rodstar - doverals.com

Transcription

RODSTAR
Modern Design and Simulation
of Rod Pumping Systems
for Deviated or Ver tical Wells
3075 E. Imperial Hwy Suite 125
Brea, CA 92821 USA
Telephone #: (562) 694-3297
Fax #: (562) 694-8641
gotheta.com
Email Addresses:
Product Manager: Kevin Lo, [email protected]
Software Support: [email protected]
Sales: Christy Kukula, [email protected]
© Theta Oilfield Services, Inc., 2014.
All Rights Reserved. This manual may not be reproduced in whole or in part without the written permission of Theta Oilfield Services, Inc.
XROD, XROD-V, RODSTAR, RODSTAR-D, RODSTAR-V, RODDIAG, XDIAG, XDIAG-V,
XDIAG-D, XBAL, XTOOLS, XANIMATE are trademarks of Theta Oilfield Services, Inc.
Third Edition, April 2014
RODSTAR | iii
Contents
Technical Support . . . . . . . . . . . . . . . . . . . v
System Requirements . . . . . . . . . . . . . . . . . v
1Introduction
1
1.1 Program Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Advanced Capabilities and Program Limitations . . . . . . . . . . . . . . . 2
1.3 Help System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Software Installation
5
2.1 RODSTAR Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Questions About Installation . . . . . . . . . . . . . . . . . . . . . . . 5
2.3 Installing the Software Sentinel. . . . . . . . . . . . . . . . . . . . . . 5
3
Starting and Setting Up RODSTAR
7
3.1 Starting RODSTAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2 Exiting RODSTAR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3 Setting up RODSTAR . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3.2 General setup options . . . . . . . . . . . . . . . . . . . . . . . 11
3.3.3 Defaults, Limits, and Rod Guide Setup. . . . . . . . . . . . . . . . 12
3.3.4 Output Options . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.3.5 Pumping Unit Options . . . . . . . . . . . . . . . . . . . . . . . 16
3.3.6 Rod Grade Options . . . . . . . . . . . . . . . . . . . . . . . . 19
3.3.7 Batch Mode Options. . . . . . . . . . . . . . . . . . . . . . . . 20
4
Running RODSTAR
23
4.1 RODSTAR’s User Interface. . . . . . . . . . . . . . . . . . . . . . . . 23
4.1.1 RODSTAR’s Help System. . . . . . . . . . . . . . . . . . . . . . 24
4.2 Entering Rod Pumping System Data. . . . . . . . . . . . . . . . . . . . 24
4.2.1 Entering Well Information Data. . . . . . . . . . . . . . . . . . . 25
4.2.2 Entering Production Information. . . . . . . . . . . . . . . . . . 27
4.2.3 Entering Pump and Tubing Information Data. . . . . . . . . . . . . 29
4.2.4 Entering Rod String Data . . . . . . . . . . . . . . . . . . . . . 31
4.2.5 Entering Wellbore Deviation Data (Deviated Mode) . . . . . . . . . . 36
4.2.6 Entering Pumping Unit Data. . . . . . . . . . . . . . . . . . . . 40
4.2.7 Entering Motor Information and Energy Cost . . . . . . . . . . . . . 50
iv | Table of Contents
5
Changing, Loading and Saving Data
53
5.1 Visual Input. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
5.2 Storing Data Files. . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
5.3 Running and Viewing the Output . . . . . . . . . . . . . . . . . . . . . 54
5.3.1 Saving the output. . . . . . . . . . . . . . . . . . . . . . . . . 56
5.3.2 Running in Batch Mode. . . . . . . . . . . . . . . . . . . . . . 56
5.4 Loading Data from Disk. . . . . . . . . . . . . . . . . . . . . . . . . 58
5.4.1 Viewing Previously Saved Output . . . . . . . . . . . . . . . . . . 59
5.5 Manipulating Input Windows. . . . . . . . . . . . . . . . . . . . . . 60
6
Rod Pump System Design
61
6.1 Understanding RODSTAR’s Output. . . . . . . . . . . . . . . . . . . . 62
6.1.1 Dynamometer and Permissible Load Plots . . . . . . . . . . . . . . 62
6.1.2 Torque Plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
6.1.3 IPR Plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
6.1.4 Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
6.2 RODSTAR (Deviated Mode) Output. . . . . . . . . . . . . . . . . . . . 70
6.2.1 Deviation Plots. . . . . . . . . . . . . . . . . . . . . . . . . . 70
6.3 Rod Pump System Design Guidelines. . . . . . . . . . . . . . . . . . . 74
6.3.1 Shallow, High Rate Well Simulation . . . . . . . . . . . . . . . . . 74
6.3.2 Selecting the Target Production. . . . . . . . . . . . . . . . . . 75
6.3.3 Avoiding Rod Compression . . . . . . . . . . . . . . . . . . . . . 75
6.3.4 Minimizing Power Consumption. . . . . . . . . . . . . . . . . . 75
6.3.5 Reducing Gearbox Torque. . . . . . . . . . . . . . . . . . . . . 76
6.3.6 Using RODSTAR for Correct Equipment Sizing . . . . . . . . . . . . 76
6.3.7 Using RODSTAR for Diagnostic Analysis. . . . . . . . . . . . . . . 77
6.3.8 Using RODSTAR for better Wellbore Designs. . . . . . . . . . . . . 77
Technical Support
Technical Support for RODSTAR is provided by
phone and e-mail to customers with a current Annual Technical Support Agreement.
The first year of technical support is provided free
with the initial purchase of a license.
Support for customers with an expired agreement
is billed at $100/hour with a one-hour minimum
per incident.
Please include the Serial Number from your Sentinel bitlock when contacting support.
Phone Support:
Monday-Friday 8:00 AM - 4:00 PM PST.
(562) 694-3297
E-Mail Support:
[email protected]
System Requirements
Processor: 1.6 GHz or higher
Operating System: Windows XP/Vista/7/8
Memory: 1 GB of RAM or higher
Hard Disk Space: 125 MB available disk space
Display: 1024 x 768 or higher
RODSTAR | v
RODSTAR | 1
1
Introduction
RODSTAR™ is a powerful, easy-to-use rod
pumping system simulator and design tool. With
RODSTAR you can design new rod pumping installations or make changes to existing rod
pumping systems. It is a tool that you can use to
compare pumping units, pumping speeds, plunger
sizes, rods, motor types, etc. You can evaluate the
effect of pump fillage, fluid level, or an out-of-balance unit. Also, you can study the effect of prime
mover speed variation, stuffing box friction, etc.
RODSTAR also allows you to combine sophisticated rod pumping system modeling with inflow
performance data for even more powerful capabilities.
There are two versions of RODSTAR: deviated
and vertical. This manual applies to both for
most items since the program’s user interface is
practically identical except for an additional input
window in the deviated version for entering the
wellbore deviation survey. The deviated version is
primarily for rod pumping systems with deviated
wellbores, while the vertical version is for vertical
wellbores (little to no deviation).
When the program discusses “RODSTAR” it
applies to both versions of the program. If there
are differences between the deviated and vertical
versions, the description in the manual will specify
the version (deviated, or vertical).
RODSTAR is very easy to use, flexible, customizable, and fast. With a single click of the mouse you
can access any input screen at any time. You can
change an input by simply clicking on it, and when
you have a question, simply press ! for context
sensitive help for any input item. You can also take
advantage of standard Windows features such as
being able to copy the dynamometer, torque plots,
or IPR plots to the clipboard and then paste them
in any other Windows document.
By taking advantage of the program’s powerful
“expert” knowledge you can save time and come
up with better answers. This makes it possible to
optimize rod string designs, find out the pumping
speed and plunger size you need for a target production, etc. in minutes instead of hours. RODSTAR makes it possible to get these answers even
with little rod pumping expertise.
1.1 Program Features
RODSTAR remembers the information you type
when you start a case from scratch. You can exit
RODSTAR while in the middle of entering data
for a new case, and RODSTAR will save the data
you have entered so far. This works the same way
if the program crashes. The next time you start
RODSTAR, the program will ask you if you want
to resume entering data. If so, you will be returned
to the data entry window you were using when you
left RODSTAR, with all the data you had entered
already in place. RODSTAR contains data for
all common pumps, rod sizes, rod grades, pumping units, tubing sizes, etc. Also, it “knows” when
you need slim hole couplings or a thin wall pump,
what rods fit in the tubing size you selected, the
maximum recommended pumping speed for any
system design, etc.
RODSTAR can read well files created with RODDIAG™, XDIAG™ (Theta Oilfield Services,
Inc.’s diagnostic computer programs) and XBAL™
(Theta Oilfield Services, Inc.’s pumping unit
balancing program). RODSTAR can read all the
data contained in a RODDIAG or XDIAG file,
including the measured dynamometer card. This
2| Introduction
allows you to redesign pumping systems without
having to reenter system data. RODSTAR can
display and print the measured dynamometer card
overlaid on the same plot as the predicted surface
dynamometer card. This feature has many uses
that include finding the correct rod-tubing friction,
or determining whether the load cell used to record
the dynamometer card may be out of calibration.
By being able to read XBAL files, RODSTAR can
get the existing maximum counterbalance moment
based on the existing position of the counterweights. This eliminates the need for a field measurement of counterbalance effect. Also, you can
enter the calculated balanced maximum counterbalance moment back into XBAL to find out how
to balance the pumping unit in one step.
RODSTAR can simulate any pumping system and
can accurately predict its performance. For a system you specify, the program predicts the surface
and downhole dynamometer cards. Also, it calculates the peak gearbox torque and gearbox loading,
structure loading, rod loading, pump stroke, minimum required pump length, plunger length, pump
spacing, expected production rate, the counterbalance needed to balance the unit, the prime mover
size, overall system efficiency, daily energy consumption, monthly electricity bill, and other useful
information. Also, RODSTAR allows you to enter
inflow performance data so that you can easily design a pumping system for any pump intake pump
intake pressure, calculate the expected production
rate, pump intake pressure and pump condition for
any rod pumping system, find out the maximum
production rate you can get, and more.
Also, in contrast to the conventional trial and error
system design, with RODSTAR you can enter a
target production and ask the program to simultaneously calculate the strokes per minute, plunger
size, and rod string design. It even recommends
the pumping unit size you need. Or, you can enter
IPR data and have RODSTAR calculate the target
production and design the system for that target
production based on any pump intake pressure or
fluid level you want.
RODSTAR comes with a large pumping unit
database so that you can easily select and compare
pumping units without having to get the unit
dimensions yourself. RODSTAR can model any
pumping unit geometry including long stroke units
such as the Rotaflex. Also, you can enter your own
pumping unit data in case your unit is not in the
program’s database. Advanced error trapping and
warning messages help prevent errors and make
you aware of special requirements necessary for
proper system operation.
RODSTAR deviaed version also allows you to
enter a deviation survey and calculates side load,
dogleg severity, rod guide spacing recommendations, etc.
After you run your case, RODSTAR will score
your design. Based on surface loading, rod string
loading, and pump performance, RODSTAR will
score the design so that you will know what sections may need improvement.
1.2 Advanced Capabilities and
Program Limitations
RODSTAR has many advanced features that enable you to accurately predict system performance
for any rod pumping system. It can simulate wells
of any depth including very deep or shallow wells.
It is the only program of its kind that models fluid
inertia effects that are present in wells that pump
incompressible fluids with larger than 2.00” plungers from depths of less than 4000 feet. The deviated mode can simulate deviated wells, while the
vertical mode can only be used for wells that are
vertical or have little deviation.
By calculating the minimum stress at the bottom
of each rod section, RODSTAR shows whether
the rods are in compression or not. This is vital for
fiberglass rods which must never be in compression
to avoid premature failures. This is also important
for steel rods since excessive compression can cause
buckling failures.
RODSTAR | 3
RODSTAR can model the effect of prime mover
speed variation and pumping unit inertia and can
accurately calculate electricity consumption and
the monthly energy bill. Because RODSTAR uses
actual motor efficiency curves, the results are very
accurate. You can use this capability to compare
the energy consumption of systems with different
rod designs, plunger sizes, or pumping unit types.
RODSTAR’s Inflow Performance Relationship
(IPR) capabilities allow you to select the IPR
relationship you want RODSTAR to use (Vogel or
Fetkovich), your can enter one to ten test points,
and can integrate IPR and rod pumping system
models to predict the maximum production rate
possible, the fluid level and pump condition for a
given pumping speed, or the target production for
any fluid level or pump intake pressure you want.
Because of all these features, RODSTAR has virtually no limitations and is the most advanced and
easiest to use program of its kind.
RSWIND.exe
RODSTAR.CDB
CUSTOM32.PUD
Files ending in .PUD
1.3 Help System
RODSTAR takes full advantage of Microsoft
Windows to bring you state-of-the-art contextsensitive help for any input field by simply press-
ing the ! key. Also, you can search help for any
other item.
Files beginning with
demo_
Files ending in .RST
Files ending in .RSVX
Files ending in .RSDX
The program file for
RODSTAR deviated
cases. It is the file that
your Desktop Icon runs
when you double-click
it.
Contains the costs for
both rods and pumping
units. Once you create
this file by entering rod
and pumping unit cost
data, you can provide
copies to other users in
your company.
This file contains the
measured pumping
unit information you
entered in Setup. Once
you create this file, you
can distribute copies
to other users in your
company.
The program’s pumping
unit database. When
updates are announced
on our Website for new
pumping units that
have been added, you
can download a zipped
file that contains additional PUD files to add
to your folder.
Several files are included that are example
cases to demonstrate
the program functions.
During installation,
there are copies of these
files placed in the folder
used when opening
case files.
Case files saved by
RODSTAR release
prior to 3.0.
Case files saved by
RODSTAR in vertical
mode.
Case files saved by
RODSTAR in deviated
mode.
4| Introduction
Files ending in .RDG
Files ending in .XDG
Files ending in .CBLX
or .XBLX
SENTINEL.INI
Case files saved by
RODDIAG.
Case files saved by
XDIAG.
Case files saved by
XBAL
For installations using
a Network license, this
file is located in the
program folder on the
client PC and has the
name or IP address of
the license server being
used.
The RODSTAR program is protected and cannot
run without a software sentinel supplied by Theta
Oilfield Services, Inc.. See Chapter 2 for details on
how to install the software sentinel.
RODSTAR | 5
2
Software Installation
Before you install the program, make sure you
have the hardware and software you need to run
RODSTAR.
RODSTAR cannot read files created with a new
version of the software.
2.1 RODSTAR Installation
Nothing. When you install or reinstall RODSTAR, only program files are replaced. The latest
version of RODSTAR saves files in the XML file
format but can read files created with older versions of RODSTAR as well.
RODSTAR can be downloaded and installed from
our website, gotheta.com. It is recommended that
you install the software into the default directory;
however, you can still select a custom directory.
If you require assistance downloadng or installing
your software, please contact support@gotheta.
com.
2.2 Questions About Installation
The following are some answers to questions you
may have about installing RODSTAR.
Do I need to uninstall previous versions of
RODSTAR before I install?
No. When updating versions of RODSTAR, the
program defaults to install to the “C:\Program
Files\Theta\RODSTAR” directory. If your previous copy of Rodstar is in another directory, you
can specify to install over it. It will not replace any
of your case files, just the old version of the program.
The installation defaults to setting “C:\THETA”
as the common folder for your case files. Using a
common folder is a good idea since several of the
Theta applications that you might have can all
share the same case files.
Although a new version of RODSTAR can read
files created with older versions, an older version of
What happens to files I have created with older
versions of RODSTAR?
What happens to the Setup Settings from previous versions?
If the previous version is not very old (before the
new setup options were developed) then your settings will be preserved.
2.3 Installing the Software
Sentinel
Your RODSTAR license is validated and protected
by a security bitlock called a Sentinel. For Standalone installations, this is a USB key that is attached to your PC. For Network Licenses, the key
is attached only to the Network License Server.
RODSTAR communicates with the sentinel and
although the program can be copied, it will not
operate without a sentinel supplied by Theta Oilfield Services, Inc..
If the sentinel is not installed correctly, the program will warn you that the sentinel does not appear to be connected. If this occurs, make sure the
sentinel in properly installed and the connection is
not loose. If the sentinel is properly installed but is
not working, it may have been damaged. Frequent
plugging and unplugging, and static electricity can
6 | Program Installation
damage the sentinel. If this occurs, contact Theta
Oilfield Services Inc. to determine if you need a
replacement. Do not discard the damaged sentinel.
Even if it is damaged, you must return it to Theta
Oilfield Services, Inc. before a replacement can be
sent out. When RODSTAR first starts, it reads
and displays the serial number of your sentinel on
the opening screen.
Theta Oilfield Services, Inc. uses Sentinel “SuperPro” and Sentinel “HASP” for software protection.
Both USB Sentinel types can be plugged into any
available USB port or hub on the PC or it can be
plugged into a network USB switch.
RODSTAR | 7
3
Starting and Setting Up RODSTAR
3.1 Starting RODSTAR
The RODSTAR installation program will put an
Icon on your Desktop and an entry in your Start
Programs for access to RODSTAR. To start the
program, simply double-click on its icon.
RODSTAR has a “getting-started” window,
shown in Figure 3.1, that appears whenever you
start the program. The window shows the most
common toolbar icons you need to know to begin
using RODSTAR.
3.2 Exiting RODSTAR
To exit RODSTAR,
double click on its
Control-menu box (upper left hand corner)
or select File and then
Exit. Another way to
exit RODSTAR is to
press A+ $. Before
exiting RODSTAR
make sure you have
stored your data to disk
(RODSTAR asks you
if you want to save the
data when you exit, if
you have changed your
data since the last time
you saved it). Otherwise
it will be lost.
The RODSTAR Window
Figure 3.2 shows the RODSTAR window that
appears when you start the program. RODSTAR
behaves like any other standard Windows program. You can use the mouse to move and size
windows, move and restore icons, select text,
choose commands from menus, and dialog boxes,
and complete almost any other task in RODSTAR
aside from typing text.
Following is an explanation of the parts of the
RODSTAR window as shown in Figure 3.2.
The control-menu box is in the upper-left corner
of each window. The control menu is most useful
if you use the keyboard. You can use the control
menu commands to resize, move, maximize, minimize, and close windows. Also, you can use it to
switch to other applications. (If you use a mouse,
Figure 3.1 - The “Getting Started” Window
8 | Starting and Setting Up RODSTAR
Figure 3.2 - RODSTAR’s main window
you can perform these tasks by clicking and dragging.) Double-clicking on the control menu box
closes RODSTAR.
dow to fill the entire screen. After you maximize
the RODSTAR window, the maximize button
shows a double box and is called the restore butThe title bar shows the name of the application and ton. Clicking on the restore button re-sizes the
RODSTAR window to the size it was before you
the name of the file currently in memory. If more
maximized it.
than one window is open, the title bar for each
active window (the one that you are working with) Using the mouse you can resize RODSTAR’s
is a different color or intensity than the other title
main windows. When you resize RODSTAR’s
bars.
window to a size smaller than required to display
all information, it will display vertical or horizonThe menu bar lists the available menus. A menu
tal scroll bars as necessary. You can use these scroll
contains a list of commands, or actions, you can
bars with the mouse to view unseen portions of
carry out with RODSTAR. For example, click on
entry windows that do not fit in the allotted space.
the Help menu to see a list of helpful choices.
The Minimize button reduces RODSTAR to an
icon. After you minimize RODSTAR, you can
reopen it by double clicking on the RODSTAR
icon at the bottom of your screen.
The Maximize button causes the RODSTAR win-
The Close button causes RODSTAR to exit. It’s
easier to click the Close button once than to select
Exit from the File menu.
The Status bar shows useful messages during data
entry, when you load a case from disk or when you
RODSTAR | 9
point to a toolbar icon.
The toolbar (Figure 3.3) gives you quick access to
menu commands using your mouse. When you
first load RODSTAR, only some of the buttons on
the toolbar are active. When you enter data or read
a file from disk, then the print button and all the
buttons that correspond to input windows become
active. If you load a file that contains output then
the report icon also activates. Otherwise, if the
file contains only input then the report icon remains inactive until you run the case. For a quick
reminder of what each toolbar button does, simply
place the mouse pointer on it. A small message box
called a “tool tip” appears that tells you what the
toolbar icon does. Also, the status bar shows more
information about the same tool bar item.
Following is a more detailed explanation of each
button on the toolbar from left to right:
New file - This is the first button on the toolbar
and shows a picture of a blank page. Click on this
button to start entering data for a new case.
Open file - This is the second button on the toolbar
and shows the standard open file icon used by most
Windows programs. Click on this button to read
a RODSTAR, RODDIAG, or XDIAG file that
was previously stored on disk.
Save file - This is the third item on the toolbar and
shows a picture of a diskette. Click here to save the
data in memory to disk. If this is the first time you
are saving this case, RODSTAR asks for a new
file name. After you save a file, or after you load
a file from disk and make changes to it, click on
this button to quick-save the data under the same
file name. To save it under a different file name
click on File on the menu bar and then select Save
As....
Setup - This is the fourth item on the toolbar.
Click here to see RODSTAR’s Setup window.
This allows you to specify inputs and preferences
that normally do not change often such as: your
company name, electricity cost, units of measure,
standard sucker rod length, custom sucker grades,
measured pumping unit data, pumping unit and
sucker rod cost, batch run options, printed report
options, and custom summary spreadsheet formats.
Well information - This is the fifth item on the
toolbar and shows a picture of a file cabinet. Click
here to open the well information window. When
you first load RODSTAR this icon (and the next
five icons) is inactive until you enter well information data or until you load a file from disk. The file
information window contains data such as pump
depth, run time, pump condition, tubing and casing pressures, fluid gravity, etc.
Production information - This is the sixth item on
the toolbar and shows a picture of a barrel. Click
here to open the production information window
that has data for items such as fluid level, pump
intake pressure, target production, IPR data, etc.
Pump and tubing information - This is the seventh item on the toolbar and shows a picture of a
downhole pump . Click here to see data for tubing
size, pump type and size, tubing anchor depth,
rod-tubing friction, and fluid inertia effects.
Rod string information - This is item eight on the
toolbar and shows a picture of a sucker rod. Click
here to open the rod string information window.
This is where you specify what kind of rod string
you want RODSTAR to design for you. Also, you
can enter your own rod string design, specify the
service factor you want to use, etc.
Deviation Survey Input - This is the ninth item on
the toolbar and shows a picture of a deviated wellbore. It is only available in deviated mode, since
this is the input window for the deviation survey
of the well. Click here see the deviation survey and
also to see the 3-D plot of the wellbore.
Pumping unit information - Click here to open
the pumping unit information window that has
data for pumping unit type, crank rotation, stroke
Figure 3.3 - RODSTAR’s toolbar
length, structural unbalance and counterbalance
data.
Motor information - This icon shows a picture of
a motor. Click here to open the motor information
window that has data for electricity cost, power
meter type, motor type and size, moments of inertia and whether to include motor speed variation.
Previous window - This icon shows an arrow
pointing to the left. Click it to go back to the previous input window.
Next window - This shows an arrow pointing to
the right. Click here to advance to the next window when entering data for the first time or when
you are changing data.
Run - This item follows the arrow icon on the
toolbar and shows a picture of surface and downhole dynamometer plots. Click here to run RODSTAR after entering all your data or after you
change an input.
Report - This item follows the run icon on the
toolbar and shows a picture of a printed page.
Click here to view the output in memory. This
allows you to view the output saved in a file you
just loaded from disk, or to return to the output
screen. If this button is inactive (dimmed) it means
that there is no output report in memory. To make
it active, run the case, or load a case with saved
output.
Email Icon - Click on this icon to email one or
more cases to Theta Oilfield Services, in case you
have questions.
Print - This button follows the Report button on
the toolbar and shows a picture of a printer. Click
it to send the output to the printer.
If you have entered data for a case, but haven’t run
the calculations yet, you can get a printout of your
input data by itself. You get the same one-page
output, except that only the input data appears on
the page.
The Print… command on the File menu allows
you to select exactly which parts of the output you
want printed. For more information, see section
3.3.4, Output Options under Setup.
Export CBM - This item is second from last on
the toolbar and shows a picture of a crank and
counterweight. This button becomes active after
RODSTAR runs or after you load a file with saved
output. Click it to place the maximum counterbalance moment for balanced conditions on the
clipboard for use in XBAL.
Help - This is the last item on the toolbar and
shows a picture of a question mark. Click this button at any time to get help.
3.3 Setting up RODSTAR
Click on the Setup button on the toolbar to open
RODSTAR’s Setup window. Another way to
access Setup is to open the Tools menu and then
select RODSTAR Setup. This window as shown
in Figure 3.5 allows you to enter items that do
not normally change from run to run. Also, Setup
allows you to customize RODSTAR by entering
your company name, default electricity cost,
custom rod grades, measured pumping units, rod
and pumping unit cost data, and a lot more. The
measured pumping unit data you enter is saved
in the CUSTOM32.PUD file in the program
directory; the cost data you enter for rods and
pumping units is saved the RODSTAR.CDB
file in the program directory. RODSTAR stores
all other information you enter in Setup in the
registry.
3.3.2 General setup options
Measurement Units
For measurement units you can select English,
Canadian, or Metric/SI. English units are mainly
used in the USA and South America. If you select
this option RODSTAR will ask for pump depth
in feet, production rate in BFPD, plunger and rod
diameters in inches, etc. The “Canadian” option
provides you with the common mix of English
and Metric units used in Canada. The “Metric/
RODSTAR |11
SI” option will cause RODSTAR to
use Metric/SI units for most inputs.
Regardless of the units you select,
you can press @ while entering
numeric data to convert from one
system of units to the other. When
you press @ to convert units, the
background of the input field box
changes color from light blue to
light green.
Show Visual Input Window
Figure 3.4 - RODSTAR’s Setup window
If you uncheck this checkbox you
will deactivate the Visual Input feaXDIAG if you do not locate the original XDIAG
ture in RODSTAR. This feature is
accessed through the toolbar or windows tab of the file.
menu bar. The Visual Input Window allows you to
select an input parameter by clicking on that part
Exit Program if Idle
of a graphical representation of the well. For more
information on the visual input feature see section This feature was primarily designed for network li5.1.
censes, but can be utilized to save your work if you
are away from your computer for a set amount of
time. If the checkbox is checked, the program will
Save XDIAG Imported Dyno Card to RODSTAR File
exit after the set amount of time. In the case of
the network license, this will release the license for
When opening an XDIAG file in RODSTAR,
the measured surface
dynamometer card is
shown in the surface
dynamometer card
graph of the output
report. This allows you
to perform a history
match to determine the
amount of friction that
is in the well. Check
this checkbox if you
would like the measured
surface dynamometer
card imported from the
XDIAG file to be saved
to the RODSTAR file.
This will allow you to
use the RODSTAR file
Figure 3.5 - Help for RODSTAR’s setup
in the future to run in
another user to use. This avoids the problem where
the license may be locked onto that computer
because the user left the software running but left
there computer for an extended amount of time.
There is also a checkbox to save your work before
the program exits in this fashion. This will allow
you to retain what you have worked on before the
program exits.
• Pump efficiency
• Pump fillage
• Pump load adjustment
• Run time
• Standard steel sucker rod length
• Steel rod service factor
• Stuffing box friction
3.3.3 Defaults, Limits, and Rod Guide Setup
• Tubing pressure
• User name
The “Defaults” input window in Setup for the
vertical mode is shown in Figure 3.6. Here,
• Water cut
RODSTAR allows
you customize the
default information
used by the program
when you begin
entering data for a
new case. You can
also change the rod
stress loading limits
used by RODSTAR
in a steel or fiberglass rod design, so
that RODSTAR
will use larger rods
rather than exceed
the loading limits
you specify.
Figure 3.6 - Setting up default quantities for the vertical mode
Any of the following
items can be customized:
• Water specific gravity
• Casing pressure
• Company name
• Electricity cost
• IPR correlation
• Motor type
• Oil gravity
• Plunger size
• Pump condition
The program uses the standard steel sucker rod
length (typically 25 or 30 ft.) to calculate steel rod
string section lengths that are evenly divisible by it.
This works whenever RODSTAR designs the rods
string (when RODSTAR calculates a steel rod
string taper design, whether for a steel rod string,
or a tapered steel rod section beneath a fiberglass.)
For Corod rod strings, RODSTAR ignores this
number. For fiberglass rods, the program uses the
standard length of 37.5 feet. Below the defaults,
you can set the rod loading threshold for steel and
fiberglass sucker rods. When RODSTAR designs
a rod string it begins with a single taper using the
smallest diameter set by the user. Once the tapers
are set, the program balances the rod string then
the program checks the rod loading against these
values. If the rod loading is more than what is
entered in these fields, it will redesign the string
with stronger rods, rebalance the string, and check
the loading against these values again. This routine
will continue until either the rod loading is equal
to or less than the values entered here, or until the
strongest rods are used.
Here you will also see a checkbox which is labeled
“Use all diameters when designing Rod String”.
RODSTAR will use a single taper in designing the
rod string if it will satisfy the lifting requirement.
In cases where the loading is low enough to warrant a single taper design, checking this checkbox
will force RODSTAR to use a tapered design with
all the diameters between and including the max
and min diameters set by the user. This feature was
designed for users that use only tapered rod string
designs.
RODSTAR |13
be selected from the option on the setup window.
Once you select a guide for RODSTAR to use,
you can specify the amount of side loading each
rod guide is designed to inhibit, and the amount
of friction that the rod guides have against the
tubing. A friction coefficient value of 0.2 models
the friction between bare steel rods against steel
tubing. To determine the friction value to use for
your selected rod guides, consult the manufacturer.
The manufacturer should be able to tell you, in
reference to the steel rod friction value, what the
rod guide friction value is for your rod guides. The
manufacturer may tell you the rod guides have 2
times the amount of friction as bare steel on steel
tubing, then you would enter 2 * 0.2 which is 0.4.
You can also specify the maximum and minimum
number of rod guides per rod. When RODSTAR
recommends the rod guide placement, it will use
the minimum number of rods per guide if the calculated number is less than the minimum number.
The same is true for the maximum rod guides per
rod. If the calculated number of guides per rod is
Figure 3.6d shows
the Defaults input
window for the deviated mode. Here,
in addition to the
default values and
rod stress loading
limits discussed
above, you can also
specify the type
of rod guides you
want to use. There
are two main options to the rod
guide selection, you
may enter the rod
guide information
manually or have
RODSTAR design
Figure 3.6d - Setting up default quantities for the deviated mode
the rod guides for
you. To have the
program design the
more than the maximum value, then the recomrod guides for you, the preferred rod guide must
mendation will use the maximum number.
3.3.4 Output Options
RODSTAR gives you full control over what is
shown on the printed output. Using the Output
Options tab in Setup, shown in Figure 3.7, you
can select the items you want included on the
output. The options you select here are the items
printed by default when you select Print… from
the File menu, or use the Print toolbar button.
from the well information window or the rod
string information by clicking those respective
buttons in this window.
♦♦
Scoring Page
This option will generate a scoring page for the
output report which displays the overall score of
the design in basic letter grade format. If there are
any areas of concern for
the design which may
have caused a low score,
the software will display
the issues here and
recommend solutions
to the problems. If
the system receives a
good score without
recommendations, then
the scoring page will not
be displayed.
Figure 3.7 - Selecting output options
The system design is
scored on the following
You can choose from among the following:
items:
This option will generate a cover page for the
output report which contains all your company
information and the recipient’s information. You
can edit what information is on this page in the
setup window under defaults. The user information
that is set in defaults (such as user name and
company name) is your information. The items
that are labeled as “Second Company” before the
item in defaults are for the recipient’s information.
For example, “Second Company Name” is the
name of the recipient’s company. To add additional
information to the cover page, you may go to the
well information window and click the “+” button
next to the comment entry field. You can also edit
the cover page after the case is ran by clicking
the “+” button on the bottom of the output report
window. After clicking the “+” button, you will
see the main cover page editing window. You can
insert items such as the well information comment
The maximum gearbox loading when the unit is
balanced. It is important to note that this score
is based on a balanced unit. If your unit is not
balanced, the actual loading will not correspond to
the loading percentage displayed in this section. Be
sure to observe the actual loading of the gearbox if
the unit has not been balanced.
♦♦
Cover Page
•
Balanced Gearbox Loading
•
Maximum Rod Loading
This score is based on the maximum rod loading
of all tapers of the rod string. For example, if the
rod string has three tapers, and each taper has a
rod loading of 90%, 99%, 47% respectively, then
the score will be based on the 99% loading of
taper two. If the loading is low, the score will be
lowered slightly because the rod string is over-sized
or over-designed. If the rod loading is overloaded
then the score is lowered severely as that will lead
to premature failure in the rod string.
•
Structure Loading
•
System Efficiency
The structure loading score is based on the peak
loading at the surface on the polished rod (peak
polished rod loading). This load is compared to the
structural rating of the pumping unit to calculate
the structural loading. Similar to the rod loading
score, the structure loading score is lowered
slightly if the unit is oversized and lowered severely
if the unit is overloaded.
This score is dependent on pump depth and
production rate. This is because the maximum
efficiency fluctuates depending on the depth
and production. To further explain, a very deep
well requires a lot of energy to lift the rod string.
Comparing the energy required to lift the rod
string to the energy required to lift the fluid (at
the given production rate) the maximum efficiency
drops. Based on this principle, the scoring of the
efficiency is adjusted so that the grade is calculated
on the appropriate scale.
•
Bottom Minimum Stress
This refers to the bottom minimum stress of
the sucker rods. This score is not affected by
the bottom minimum stress of sinker rods or
sinker bars. If the bottom minimum stress on
the sucker rods is negative, the score is lowered
because compression in the sucker rods may cause
buckling. Buckling rods can cause tubing leaks
and premature failures. If the stress on the bottom
minimum stress of the sucker rods is high, the
score is lowered slightly. This is because the sinker
bars are too long, which cause the high tension
on the bottom of the sucker rods, and the well
requires more energy to lift throughout the cycle
than necessary.
•
Minimum Polished Rod Loading
The minimum polished rod load is used to
determine this score. If the minimum load on
the polished rod is negative, the score is lowered
because the rod string will float. A floating rod
string is where the pumping unit begins the downstroke and, due to friction or speed of the pumping
RODSTAR |15
unit, the rod string doesn’t follow carrier bar and
separates from the pumping unit. This causes a
severe problem where the system will suffer a
shock at the bottom of the stroke as the pumping
unit begins the upstroke and the rod string comes
down on the carrier bar. The effect is like a very
large hammer, with the weight of the rod strong
and fluid over the plunger, hitting the top of the
carrier bar on each stroke.
♦♦
Input data and calculated results
♦♦
Cost analysis
♦♦
Inflow performance (IPR) chart
♦♦
Dynamometer cards and Torque Plots
This option prints one page showing all the input
data and the results of the calculations, as well
as miniature predicted dynamometer and torque
plots.
This option prints both the rod string and the
pumping unit costs. You must already have entered
the costs into RODSTAR’s cost database (see section 3.3.6, “Cost Database,” on page 23 for more
information).
Selecting this option gives you an additional page
with the IPR plots, the IPR data including the test
points, and a table of pressure versus production.
Selecting this option prints a separate single page
containing the predicted surface and downhole
dynamometer cards with the predicted permissible
load diagram. It also prints the net gearbox torque
plots for existing and balanced conditions on the
bottom half of the page. The dynamometer card
plot may also show the actual (measured) surface
dynamometer card (if you loaded a RODDIAG or
XDIAG case into RODSTAR).
Additional items on Output Options:.
♦♦
Deviation Charts
If selected, it will add a page with deviation related
charts such as side load as a function of measured
depth, axial loading, buckling tendency, dogleg
severity, and the wellbore trajectory views from
North to Looking down.
♦♦
Recommended Guide Report
♦♦
Measured Deviation Survey
This will print a report of rod guide placement
(depending on type of rod guides selected in the
“General” section of setup).
Selecting this option will add pages which show
the entered deviation survey. This is helpful if you
need to send the results to a customer or coworker
that does not have the digital file. If they need to
recreate the case, the deviation survey is included
with the rest of the well information.
♦♦
Overlay actual (measured) dynamometer card
If you load a RODDIAG or XDIAG case into
RODSTAR, the program can plot the surface
dynamometer card that was stored in the RODDIAG or XDIAG file on the same plot as the
predicted dynamometer card.
♦♦
Omit Dyno cards and Torque Plot from
calculate results page viewing
Select this option if you would like to remove the
dynamometer cards and torque plot graphs from
the calculated results page. No other data will be
removed from the calculated results page other
than these graphs from the bottom of the page.
units displayed by the program at the pumping
unit selection window. Here you can select the
pumping unit manufacturer and the pumping unit
sizes you have for each manufacturer in the field.
After you customize the pumping unit list, you can
select pumping units faster since the program will
only show the units you have in the field instead of
displaying all the pumping units in the pumping
unit database. This saves you time by minimizing
the time and effort required to select a pumping
unit. For example, if you only have 12 different
sizes of Lufkin Conventional, 10 sizes of Mark
II, and 14 American Conventional unit sizes, you
can setup RODSTAR to show only these units in
the pumping unit selection screen. To customize
RODSTAR’s pumping unit list, do the following:
1. Click on the “+” symbol on the left of “Pumping Unit Options.” Then, click on “Custom
pumping unit list”. This opens the window
shown in Figure 3.8.
2. Drop down the manufacturer list by clicking
on the down arrow next to “Manufacturer:”
3. Select a manufacturer you want to add to your
custom pumping unit list as shown in Figure 3.9. If this is a new manufacturer for the
custom list, all available pumping units will
appear in the window on the right side of the
screen.
3.3.5 Pumping Unit
Options
Under this item, there
are two sub-items,
Customize Pumping
Unit List, and Measured
Pumping Unit List. Let
us take a look at each of
these items:
♦♦
Customize
Pumping Unit List
This option allows you
to customize the list of
Figure 3.8 - Customizing the pumping unit database
RODSTAR |17
first).
5.
To remove a
unit from the customized list, simply drag
it from the list on the
left, and drop it in
the list to the right.
Or, you can click on
a unit once and then
click the Remove>>
button (in the middle
of the screen). To
make sure you select
the correct pumping unit, highlight it
Figure 3.9 - Selecting a manufacturer
(click on it once with
the mouse) and the
4. You can select the units to include in the cusName: and Other:
tom pumping unit list using drag and drop. To
fields on the bottom of the screen will show
add a unit from the list of available units to the
additional information about the pumping unit
custom database list, you simply drag (click on
as shown in Figure 3.10. This is especially useit with the mouse and hold the left mouse butful for manufacturers (for example, American
ton while moving it) the units you want from
conventional) who have more than one unit
the list on the right to the custom list on the
with the same designation but different crank
left. Or, you can click on a unit once to select
types. In such a case, the Other: field shows
it, and then click on the <<Add button (in the
the crank type of the unit or other information
middle of the screen). The program automatithat helps identify the pumping unit type. This
cally arranges the units in the proper order
is not the only way to customize the pumping
(largest stroke length and largest gearbox size
unit database. As
discussed in the section dealing with the
pumping unit information screen, you
can also select a unit
you want to add to
the customized unit
list by first selecting it from the full
database and then
selecting to use the
custom pumping unit
list. At that point
RODSTAR will ask
you if you want to
Figure 3.10 - Customizing the pumping unit database
add this unit to the
custom pumping unit
database. If you do, then select Yes.
6. After you are done customizing the pumping
unit list, click on OK.
of the pumping unit dimensions (see Figure 3.12).
To get more information on any of the dimensions
you see, simply click on it with the mouse. For example, you can click on the “P” box to see detailed
help on the P dimension. Also, you can click
on the “See Also” hot
button to get help for
any other pumping unit
related item.
3.3.6 Rod Grade Options
Entering Custom Rod
Grades
Figure 3.11 - Entering custom pumping unit information
♦♦
Measured Pumping Unit List
following:
To enter a rod grade
that is not in the program’s database, do the
Here you can enter data for pumping units that are 1. From the setup window, click on “Custom
not in RODSTAR’s main database. If you have the
Rod Grades.”
dimensions you need for these units you can enter
2. To add a new rod grade, click on the “+” button
them here to make them a permanent part of your
(to the left of the pencil icon). This opens up a
RODSTAR software. To enter dimensions for a
new window where you can enter the name of
pumping unit, do the following:
the rod you want to add, the tensile strength,
1. Click on “Measured Pumping Unit List”.
and the stress analysis method you want RODSTAR to use for this rod as shown in Figure
2. Click on the “+” symbol (on the left of the pen3.13.
cil symbol). This will open the window shown
in Figure 3.11.
3. Enter the data in this window starting with the
pumping unit manufacturer name.
4. Enter the pumping unit data for your pumping
unit.
5. When you are done entering data click on
“OK”.
If you need help with one of the items you have
to enter, press ! to get context sensitive help on
that item. For example, if you press ! when you
are in one of the pumping unit dimension input
fields, the program will show you an outline drawing of the pumping unit with a visual explanation
3. You can also specify that this is a sinker bar by
clicking on the “Sinker bar” option at the lower
left hand corner of this window.
4. Enter the rest of the information for the rod
you want to add and then click on the “OK”
button.
RODSTAR allows you to select any of the available stress analysis methods. Once you enter a
special rod grade to the program, it becomes part
of the program’s equipment database and it works
exactly the same way as RODSTAR’s built-in rod
grades.
For example, once you enter a special rod grade,
you can enter cost information for it, and you can
RODSTAR |19
in Figure 3.15, after
you select the manufacturer, RODSTAR
displays a mini-spreadsheet that you can use
to enter pumping unit
costs. To enter the cost
for a pumping unit,
click on the cell to the
right of the pumping
unit and enter the cost.
When you are done
entering pumping unit
costs for the pumping
units you want, click
on OK. Or, if you
want to enter rod string
cost data, Select “Rod
string costs” and then
select the rod type and
rod grade. RODSTAR
Figure 3.12 - Custom pumping unit help
will display a minispreadsheet for you to
select it from the same rod grade menu that RODenter the cost per foot (or per meter) for each rod
STAR uses for the built-in rod grades.
diameter as shown in Figure 3.16. You do not have
The modify (Pencil Icon) and delete (“X” Icon)
to enter cost data for all the rod diameters you see.
options allow you to change or erase custom rod
Simply enter the cost only for the rod grades and
grades you have already entered.
diameters you use.
3.3.7 Cost Database
When you click on this
item in Setup, RODSTAR displays a window,
shown in Figure 3.14,
that allows you to enter or
change pumping unit or
rod string costs. To enter
or change pumping unit
costs select “Pumping
unit costs” This makes
the window change by
showing a drop-down list
box that you can use to
select the pumping unit
manufacturer. As shown
Figure 3.13 - Entering custom rod grade information
3.3.7 Batch Mode Options
When you click on this
tab, RODSTAR displays
a setup page that allows
you to choose different
options relating to the
batch run capabilities of
RODSTAR. The top portion of this input window allows you to select
whether you want RODSTAR to print the results
of each case it runs in
batch, whether to create a
summary spreadsheet file,
Figure 3.14 - Cost Database Setup Window
or whether to rerun cases
output” check box, RODSTAR will not rerun
that contain saved output.
cases that have saved output. When you run
Also, it lets you choose what action to take when
RODSTAR in batch mode, RODSTAR saves
you load a file that contains custom rod grades as
the output in the same file as the input data. Also,
shown in Figure 3.17. For example, if you want
when you run one case at a time, you can save
to update the setup information with the data in
the file, then select the option “Update Setup with the output by saving the file to disk when you are
looking at the output. The option to avoid rerunfile’s information.”
ning cases that contain output is useful when you
If you check the Make Printouts check box,
want to create more than one spreadsheet file using
RODSTAR will print out every case you run
different spreadsheet formats. Once the files have
in batch. If you check
the Create summary
spreadsheet check box,
RODSTAR will summarize the results of all
the files you run in batch
in a Excel spreadsheet
file. If you select the
option “View spreadsheet
file”, after you run several cases with the batch
process, the program will
automatically create an
Excel spreadsheet and
will load it into Excel
automatically.
If you check the “Don’t
re-run cases with saved
Figure 3.15 - Pumping unit cost database
RODSTAR |21
been run with batch, each
file will contain all the
output calculations.
For example, let us assume
that there are two different users (John and Paul)
who are running RODSTAR and they each have
their favorite spreadsheet
formats. John can run 20
cases in batch mode and
create a spreadsheet that
summarizes the values he
is interested in. Later Paul
can run the same cases in
batch mode and create a
Figure 3.16 - Entering rod string cost in Setup
spreadsheet with the items
he is interested in which are
button to exit Setup.
different that John’s. Since John ran all 20 cases,
the files now contain both input and calculated re- If you have not created any spreadsheet formats,
the only format that appears is the (Default)
sults. When Paul runs the same cases in batch, he
format that RODSTAR will use when you run it
checks the Don’t re-run cases with saved output
in the batch mode and choose to create a summary
option to save time. Since the output results are
already saved in the RODSTAR files, Paul’s batch spreadsheet file. To create a new spreadsheet forrun will proceed very quickly since all RODSTAR mat click on the ”+” button. This opens the spreadsheet setup window that you see in Figure 3.18.
has to do is extract the calculated values that Paul
specified in his spreadsheet format from these 20
The list on the left side shows the columns that
cases.
are in the spreadsheet now and their order. The
Creating and/or Changing
spreadsheet formats
As shown in Figure 3.17,
you can click on the “+”
icon at the “Spreadsheet
Setup” section of the
batch window to add a
new batch spreadsheet
format (design of the
spreadsheet). Also, this
section lists the spreadFigure 3.17 - Batch mode options
sheet formats you have
saved. To use one of these
spreadsheet formats for your next batch run, high- list on the right shows additional variables you
light it by clicking on it and then click the OK
can add to the spreadsheet. You can use drag and
drop to move an item
from one list to the
other. For example, to
add rod string cost as
the last column in the
spreadsheet, locate it on
the table on the right
(variables are listed in
alphabetical order) and
drag it (click and hold
while moving with
the left mouse button) to the other side.
When you drag a value
Figure 3.18 - Spreadsheet setup
into the table on the
left, the cursor shows
an arrow that shows
where this new value will be added. After you drop
the new item in the spreadsheet table, it remains
highlighted. Then, to move it up or down in the
list click on the Move Up or Move Down buttons
below the list of spreadsheet variables. Or, you can
click on the Remove>> button to send the highlighted variable back to the “Available values” list
on the right.
Another way to add items to your spreadsheet is by
highlighting a value on the list on the right, highlighting a value on the list on the left, and clicking
the <<Add Before or <<Add After buttons in the
middle of the screen. However, using the mouse is
much easier. After you are done designing the format of the spreadsheet, you can save it by entering
a name for it in the Format name: field at the bottom of the screen. Then click OK to return to the
previous screen. From here, you can create another
spreadsheet format, or modify or delete one of the
existing formats.
To modify an existing format, click on its name
and then click on the edit icon (pencil). Or, to delete an existing format, highlight it, and then click
on the delete icon (X).
4
RODSTAR |23
Running RODSTAR
To start RODSTAR, double click on its icon.
After a few seconds you will see RODSTAR’s
introductory window and then the RODSTAR
main window. When RODSTAR first loads, only
the new file, open file, setup, and help buttons are
active on the toolbar. If you have not set up RODSTAR then do so before entering a new case (see
Chapter 1 for information on setting up RODSTAR).
example, all Windows programs have a menu bar
with drop-down menus and a control menu box at
the top left corner. You can access all menu items
using either the mouse or the keyboard. Using the
mouse is by far the easiest way.
4.1 RODSTAR’s User Interface
♦♦
An item followed by an ellipsis (...) needs
more information before taking action; normally,
the additional information is entered into a dialog box. (For example, click on File and click on
Open…)
RODSTAR has a user-friendly interface that
simplifies and speeds up data entry. The program
uses standard Windows features along with other
unique features we designed to make entering and
changing data as easy as possible. Figure 4.1 shows
how to access the most recently saved files and
select the file you want to load into RODSTAR.
If you are not familiar with Microsoft Windows,
please take some time to study your Windows
manual. Teaching you
how to use Windows is
beyond the scope of this
manual (although many
Windows procedures are
explained). By taking the
time to understand and
learn how to use Windows, you will be able to
effectively use not only
RODSTAR, but any other
Windows program.
RODSTAR’s interface
has most of the elements
that are common to all
Windows programs. For
When selecting an item from a menu, visual clues
tell you what will happen next.
♦♦
An item followed by no markings starts an
action. (For example, click on File and then click
on New.
An easy way to load files you recently saved:
RODSTAR has a most-recently-used file list on
the File menu, as shown in Figure 4.1. Selecting
Figure 4.1 - The most recently saved file list
24 | Running RODSTAR
the Recent Files sub-menu will show you up to
nine of the most recently accessed files. A file is
placed at the top of the list whenever it is loaded,
or saved with a new name. This list can also be accessed by clicking on the drop-down button on the
toolbar to the right of the open file icon.
diagram, press “P” and then click on Permissible
load diagram.
4.1.1 RODSTAR’s Help System
4.2 Entering Rod Pumping System
Data
RODSTAR has a powerful help system that provides context sensitive help for every input item.
Also, it allows you to easily locate help on any
subject relating to system design and simulation. It
even includes a complete artificial lift glossary that
provides instant access to definitions for hundreds
of artificial lift terms. Also, the help system helps
you learn how to use it by including extensive help
on itself.
RODSTAR has context sensitive help for each
input item. To access the help, simply press !
while in the input field in question.
When entering data in RODSTAR’s input windows, it helps to know the following:
♦♦
To replace the contents of an input box,
Click on the Help drop-down menu to see the
Help menu choices which are:
♦♦
Contents..
♦♦
Search..
♦♦
♦♦
Index..
About RODSTAR..
To see RODSTAR’s version number, and your
sentinel’s serial number, click on About RODSTAR..
Click on Contents to see a list of items RODSTAR can provide help for. As you can see, RODSTAR shows text and pictures in its help screen.
For example, RODSTAR displays a picture of the
toolbar and instructs you to click on the button you
want help for. Using the mouse, you can resize or
move the Help window.
Next, click on Help and then click on Glossary to
see an alphabetical listing of artificial lift terms. To
see the definition of any of the terms in the glossary, click on it. For example, click on API gravity to see a definition. Also, you can click in the
list of items in the Glossary and then type a letter
to go to the terms that start with that letter. For,
example, to find the definition for Permissible load
Figure 4.2 - RODSTAR’s Artificial
Lift Glossary
RODSTAR |25
Figure 4.3 - The Well Information input window
double click it before typing in it.
♦♦
If an input window contains a name that is
made up of more than one word, double click any
word to select it. Then, to replace it, simply type a
new word.
To enter rod system data in RODSTAR for the
first time, click on the first icon on the toolbar or
open the File menu and select New. This opens
the Well Information input window, shown in
Figure 4.3. You can move this window with the
mouse by dragging it to the desired location. Also,
you can use the mouse to resize this input window.
RODSTAR’s input windows use the following
unique color scheme:
♦♦
Required data input fields appear with a
yellow background. You must enter data in these
fields before closing the window, continuing to the
next window, or running the calculations.
♦♦
The active input field or list box appears in
cyan.
This color scheme helps you to easily see what data
you need and where you are in the input window.
ing data in fields with yellow background color,
their color changes to white when you move to the
next field.
You can get context sensitive help for any input
field by pressing !. Please use the context sensitive help as often as possible because it contains
important information that will allow you to make
better use of RODSTAR. Also, the context sensitive help makes you aware of program assumptions
or limitations.
4.2.1 Entering Well Information Data
If you entered a company name in Setup, it appears
in the Company name field. This saves you from
having to enter the same company name every
time you enter data. The date defaults to the date
in your computer’s memory. If the date in your
computer is not correct, you can type over it. The
well name is required because RODSTAR uses it
to create the default file name when you save data
to disk.
There are two ways of moving around in an input
window. You can click the input field you want,
The pump condition panel allows you to select
pump condition and pump efficiency or pump
fillage. To select one of these input fields click on
press S+ T to move backwards. After enter-
The option to have the pump condition and fillage
or you can enter data in order by pressing T to
move forward from field to field. Also, you can
the input field or its label. Press ! while in one of
these fields for some useful information.
calculated works along with the Production Information window. When you select this option you
must enter a pumping speed and IPR data in the
second input window. Based on the SPM you enter, RODSTAR calculates the pump displacement
versus maximum available production from the
IPR data as well as the final pump intake pressure.
RODSTAR uses an iteration scheme to converge
to the correct pump condition and pump fillage
that will result from the SPM you enter, along
with the calculated pump intake pressure.
The Production Information window also gives
you the option of having RODSTAR calculate the
required pumping speed based on a target production you enter. However, the option of calculating the SPM from your target production is
only available if you select a full pump. For fluid
pound or gas interference, you must enter a pumping speed in the Production Information window.
Other input data in the Well Information window:
Comment
You can enter a comment about the case. You can
type up to 100 characters in the comment field.
The comment string you enter is included on the
screen and printed outputs.
Pump Load Adjustment (Vertical Mode Only)
The pump load adjustment allows you to increase
the fluid load picked up by the plunger. Usually
this is unnecessary. However, this input allows you
to account for extra downhole loads due to excessive downhole friction (for example due to wellbore
deviation), or due to the “plunger effect” of large
sinker bars. It is recommended that you use zero
for this number unless you have more than 1000
feet of large sinker bars such as 15/8’’ or 1¾’’ bars
in 2’’ tubing. The value of this number in pounds
is typically 5% to 10% of the pump depth in feet.
For example, for a pump depth of 6000 feet, enter
a value of 300 to 600 pounds (but only if you use
more than 1000’ of large sinker bars). RODSTAR
will not allow you to enter a value that is larger
than 15% of pump depth. Also, you can use this
input to add pump load for more conservative
predictions.
Please note that RODSTAR assumes that the
tubing-casing annulus is full of oil. It calculates the specific gravity of the oil from the API
gravity you enter. If you do not agree with this
assumption then change the oil API gravity
to correspond to the specific gravity you want
RODSTAR to simulate. For example, if you
want to simulate water in the casing-tubing
annulus instead of oil, then enter an API
gravity of 10 (which corresponds to a fluid
specific gravity of 1.0).
Percent water cut
The percent water cut input along with oil API
gravity allows RODSTAR to calculate a default
specific gravity for the produced fluid. Also, it uses
this data to calculate $/bbl (or $/m3) electricity
costs.
Oil API gravity
RODSTAR uses the oil API gravity to calculate
fluid load on the plunger and the default specific
gravity of the produced fluid. Also, as discussed
above, RODSTAR uses this number to calculate
the specific gravity of the fluid in the casing-tubing
annulus which it assumes to be 100% oil.
Fluid specific gravity
RODSTAR uses the oil API gravity and percent water cut you entered to calculate the default
specific gravity of the produced fluid. The program
will display this value when it prompts you to enter
the fluid specific gravity. RODSTAR calculates
the default specific gravity without considering free
gas. This is okay for designing new wells since we
prefer to be more conservative. However, if you
want to simulate an existing system that produces
gas, you must enter a lower number than the one
RODSTAR |27
calculated by RODSTAR. With some experience
and with “history-matching” between predicted
and actual dynamometer cards you can come up
with effective specific gravities that will accurately
model your rod pumping systems. If you use a
specific gravity that only considers liquids, it will
result in higher predicted loads, power consumption, etc.
or you can select to calculate the target production
from inflow performance data.
If you are designing a new system and you are not
sure what the specific gravity is, use the higher
value you expect to have to make sure that your
system will not be overloaded when in operation.
However, when matching measured dynamometer
cards, use a specific gravity that is as close as possible to the actual value.
If you choose to enter IPR data, the Production
Information window expands to reveal the data
you must enter. This includes the correlation you
want to use for the inflow performance relationship
(IPR), the depth from surface to the middle of the
perforations, the static bottom hole pressure, and
bubble point pressure. Also, you can enter from
one to 10 test points. If you select to use the Vogel
method for the oil IPR calculations then you only
need one point. If you use Vogel and enter more
than one point, then only the first point is used.
You can enter more than one test point if you use
the Fetkovich method. The pressure that corresponds to each production test point can either
be pump intake pressure or flowing bottomhole
pressure (in the middle of the perfs). To add a new
pair of Pi and Fluid production data, click on the
add button (top right) icon. To delete a set of data
points, click on the remove icon (bottom right).
Remember that pressing @ converts to the opposite system of units. For example, if you selected
English units but want to enter the pump depth
You can get help for any input item by pressing !
when in the input field or by clicking on the question mark icon on the toolbar.
After you finish entering data for the Well Information window click on the next screen button
(right arrow) on the toolbar to open the Production
Information input window. To move back to the
previous window, simply press the left arrow icon
on the toolbar.
in feet, press @ before entering the value. If the
value for any field with units
has already been entered,
If you do not know what the bubble point pres-
pressing @ will show it in
the opposite units.
4.2.2 Entering Production
Information
The Production Information
input window allows you to
enter a fluid level or pump
intake pressure as shown in
Figure 4.4. Also, you can
select to enter a pumping
speed, enter a target production (the program will calculate the pumping speed to
get the target production),
Figure 4.4 - The Production Information input window
on the screen by clicking on the Print button
at the bottom right hand
corner of the screen, or
you return to the production information screen by
clicking on Close.
RODSTAR offers you the
option to enter the value
of n for the Fetkovich IPR
correlation as shown in
Figure 4.6. The window
includes a check box,
labeled Calculate ‘n’, that
tells RODSTAR whether
you want to enter the
value or have RODSTAR
calculate it from your
data. If you enter only one
test point, RODSTAR
uses a value of 1.0 for n
Figure 4.5 - The inflow performance relationship (IPR) plot
unless you select to input
your own value. However,
sure is, but you know the well is producing below
if you enter two or more
the bubble point pressure, then leave the bubble
test points, RODSTAR calculates n from a log-log
point pressure field blank and click on “Producing plot.
below bubble point” or in the check box next to
If you enter inflow performance (IPR) data,
it. After you enter the last piece of IPR data, click
to a different input field, press T or click on the
“Update prod.” button to allow RODSTAR to
calculate the maximum oil, water, and fluid production rates and target production.
You can see the IPR plot by clicking on the IPR
Plot... button (under the target production field).
When the IPR plot is displayed as shown in Figure 4.5, you can move the cyan line that you see
on the plot with the mouse to see the calculated
production rate for any bottomhole pressure. To
move this line, point to it with the mouse until the
mouse cursor changes shape and then drag the line
to any pressure point on this plot. As you are moving this line, the producing bottom hole pressure,
pump intake pressure, oil production, water production and total fluid production are dynamically
recalculated. You can print the IPR plot you see
Figure 4.6 - Fetkovich ‘n’ value
RODSTAR can calculate the pump intake pressure using the target production you have entered
(see Figure 4.7). You can select to have RODSTAR calculate the pump intake pressure from
the IPR data, or if there is no IPR data available,
you can enter a pump intake pressure or fluid
level yourself. Usually, for new systems, it is recommended that the system be designed for the
highest possible fluid load on the plunger. This is
accomplished by entering a fluid level that is equal
to pump depth.
RODSTAR |29
4.2.3 Entering Pump and
Tubing Information Data
Figure 4.7 - Options for calculating pump intake pressure
On the third input
screen, you can select
the rod-tubing friction for you. The friction factors
the tubing size, tubing
calculated by RODSTAR are estimates for average
anchor depth (if anchored), pump type, plunger
friction for a vertical wellbore. If you are simulatsize, and the upstroke and downstroke rod-tubing
ing a system with excessive downhole friction, you
friction coefficients. Also, for shallow, high rate
must enter your own rod-tubing friction coeffiwells, you can include fluid inertia effects. If you
select to include fluid inertia1 effects then you must cients for more accurate results. There are several
also enter the fluid compressibility index. For more downhole conditions that increase rod-tubing friction such as: wellbore deviation, a well with heavy
information on this option read the discussion
that follows later in this section, or use the context oil production, paraffin or scale problems, etc.
sensitive help system.
The most accurate way to figure out the rod
tubing friction in RODSTAR is to imYou can select the pump plunger size from a list
port a measured dynamometer card from a
of standard sizes, or you can enter a non-standard
RODDIAG or XDIAG file. Then, “historysize by selecting “Other” from the list of plunger
match” this actual card by manually adjustsizes. If you are simulating a full pump and you
ing the friction. You do this by varying the
entered a target production, you can select to have
upstroke and downstroke rod-tubing fricRODSTAR recommend the pump plunger size for
tion coefficients until the surface dynamomyou. This option is only available when you enter
eter card predicted by the program matches
a target production and select full pump for pump
the measured dynamometer card. This
condition.
technique allows you to find the rod-tubing
Please note that the pump type you select affects
friction that gives the best results when
the plunger size that the program will recommend.
simulating this system. From then on you
It may be interesting to make one run with an
can use these friction factors every time you
insert pump type and one with a tubing pump to
simulate this pumping system.
see what RODSTAR recommends.
Please note that this “history-matching” technique
works only if the dynamometer card that you measure corresponds to a pump condition that RODOther input data in the Pump and Tubing Information STAR can simulate (full pump, fluid pound, or gas
window:
interference). For example, if the pump is worn out
or is hitting up or down, etc., then this technique
Rod-tubing friction coefficients
will not work as well. This is because you will be
For rod-tubing friction , the vertical mode allows
unable to get a good match between predicted and
you to enter upstroke and downstroke friction
measured dynamometer cards.
coefficients yourself, or you can have the program
If you do not have a measured dynamometer card,
calculate them for you. If you do not know what
to enter, then choose to have RODSTAR calculate use the following guidelines for entering rod-tubing friction coefficients in RODSTAR:
1
Fluid inertia effects are dynamic effects
that increase fluid load on the plunger in wells less
1. First select to have RODSTAR calculate the
than 4000 feet with pump plungers larger than 2.0
rod-tubing friction coefficients for you. You
inches
can use these calculated values as guidelines to
decide what values to enter yourself to better
simulate your rod pumping system.
friction coefficient. For example, the friction ratio
default value for molded rod guides is 1.5. This
means that if you use molded rod guides, you need
2. For heavy oil or for wells with paraffin or scale to increase the rod-tubing friction coefficient by
50% to accurately simulate the additional rodbuildup, use 2-3 times the value calculated by
tubing drag. So, if you use molded rod guides,
RODSTAR. You can use the same guideline
for deviated wells when the deviation is close to you need to enter a friction coefficient of 0.3
(0.2*1.5=0.3) for the section of the rod string with
the bottom of the wellbore.
the molded rod guides.
3. For deviated wells with the deviation close
Rod guide manufacturers need to provide you with
to the surface you may need to enter a larger
number such as 4-6 times as high as the values friction ratio values for the different rod guides
they make.
calculated by the program. Also, it may be
appropriate to use different values for upstroke
and downstroke frictions to better match your
Buoyancy effects
downhole conditions.
The option to include buoyancy effects should
The above comments refer to the vertical mode.
be left unchecked in most cases. This is because
The deviated mode can calculate the effect of
buoyancy does not cause buckling of the rod string.
deviation (such as side load) from the deviation
However, for fiberglass-steel rod strings, after the
survey.
design is finalized, It is recommended that an additional run be made including buoyancy effects to
ensure that the fiberglass portion of the rod string
RODSTAR Friction Coefficients
is not in compression. If it is in compression, then
In the deviated mode, the upstroke and downmore sinker bars must be used, the pumping speed
stroke rod-fluid damping coefficients on the pump need to be reduced, or both.
and tubing information window are only for fluid
damping on rods. Also, the deviated mode allows When buoyancy is not included, the bottom of
each rod section except the last section should have
you to enter rod-tubing friction (drag) coefficients
a positive stress. Otherwise the rods may be going
for each rod string section in the rod string input
into buckling. It is normal for the very bottom of
window. The default bare rod rod-tubing drag
the rod string to be in compression if you enter a
friction coefficient is 0.2. The range for this value
pump friction that is not zero (a minimum pump
is from 0.1 (for oil lubrication between smooth
friction of 200 lbs is recommended).
rods and tubing) to 0.3 (for high water cut wells
and rough rod and tubing surfaces). Again, the
For more information on the theory behind these
best way to determine what to use is by plotting a
recommendations, please read SPE paper nummeasured dynamometer card on the same plot as
ber 25416 “Interpretation of Calculated Forces on
the predicted dynamometer card and changing the Sucker Rods” by J. F. Lea and P. D. Pattillo. Prevalues of the rod-tubing friction coefficients for
sented at the Production Operations Symposium
each section of the rod string. You can do this by
in Oklahoma City, March 1993.
loading a RODDIAG or XDIAG file into RODSTAR.
To simulate the effect of rod guides, you need to
adjust the friction coefficients for each section
of the rod string. You can use the ratio of guide
friction to bare rod friction to adjust the default
Fluid inertia effects
If the well depth is less than 4250 feet and the
pump plunger size is larger than 2.00 inches,
RODSTAR allows you to consider fluid inertia
effects. These dynamic effects become important
in wells with plungers larger than 2.0” and pump
depths of 4000 feet or less. However, there is no
exact “magic” depth for which fluid inertia becomes important. Therefore, RODSTAR allows
you to include these effects for wells up to 4250
feet deep and with a plunger size equal to or larger
than 2.0”. Another important factor is fluid compressibility. The more compressible the fluid is, the
less prominent the fluid inertia effects are.
If you include fluid inertia effects, RODSTAR will
prompt you for the fluid compressibility index. The
default is 3 but you can vary this number between
1 and 7 (x10-6 psi-1). The compressibility index
tells RODSTAR how compressible the fluid in the
tubing is. The value of the compressibility index
affects the shape of the predicted dynamometer
cards (surface and downhole). If you are not sure
what number to use, experiment with different
values until you can match measured dynamometer
cards for the well you are simulating. When you
include fluid inertia effects, pump efficiency becomes
a variable that affects the dynamic fluid load on the
plunger. Therefore, using 90% pump efficiency gives
higher peak polished rod load than using 80%.
The option to include fluid inertia effects is only
available if you are modeling a full pump. Please
do not confuse fluid inertia effects with the moments of inertia of the pumping unit that have to
do with gearbox torque due to prime mover speed
variation. Fluid inertia effects refer to additional
dynamic forces on the plunger caused by the
pickup and rapid acceleration of the fluid load.
RODSTAR simulates fluid inertia effects with
a second wave equation that models the pressure
waves in the fluid in the tubing. This increases
simulation accuracy by accounting for pressure
pulses traveling up and down in the tubing fluid.
These pressure waves have a direct affect on the
pump plunger. Since the program has to do many
additional calculations when you include fluid
inertia effects, RODSTAR may take 60%-80%
longer to run.
RODSTAR |31
4.2.4 Entering Rod String Data
The fourth input window deals with the rod string
design. As Figure 4.8 shows, you can select one of
the three available rod string entry options:
RODSTAR Steel design, RODSTAR FiberglassSteel design, or Manual rod string entry. The
symbols for these options are explained in Figure
4.8.
Figure 4.8 - Rod string entry options
RODSTAR Steel Design
If you select this option, RODSTAR displays
a window such as the one shown in Figure 4.9.
Here, you can select the maximum and minimum
rod diameters to consider, whether to include
sinker bars, the service factor, and additional rod
costs.
If you want to include sinker bars then you must
enter the diameter and length of the bar (or sinker
rod). RODSTAR does not calculate the length of
the sinker bar section because there is no industry
consensus on how to design sinker bars. However,
RODSTAR will design the rod string above the
sinker bar section you specify.
RODSTAR attempts to design an optimum rod
string based on the rod grade and the maximum
and minimum rod diameters you enter. First,
RODSTAR figures out how many rod tapers are
needed. Then, it automatically adjusts the length
of each section until the stress loading is the same
at the top of each rod section. This equalizes and
minimizes stress loading on the rod string. This
“stress balancing” approach gives the lowest cost
rod string with equally distributed stress loading,
for the rod grade you select.
This approach works the same regardless of steel
rod grade or type. For example, you can have
RODSTAR design a Corod rod string for semi
elliptical “Ultra” Corods using a maximum diameter of 17/16”, a minimum diameter of 13/16”, and
a 375’ section of 1 5/8’’ sinker bars on the bottom. RODSTAR uses only the rod sizes it needs.
For example, if the loads are not high enough to
require the use of the 17/16” rod diameter then
RODSTAR will go to the next size (16/16”). If
this is still too big, it will use the 15/16”.
The maximum rod loading used by RODSTAR
to decide when the next larger diameter rods
are needed is 95% by default. However, you can
change this number if you like by going to the
Setup “Defaults” window.
Fiberglass/steel RODSTAR design
If you select the option to have RODSTAR design
a fiberglass-and-steel rod string, you will see the
data input screen in Figure 4.10. For example, let
us say you want to use a design with fiberglass rods
on top followed by a tapered steel section with 1”
and 7/8” rods, and then 375 feet of 1” sinker bars.
RODSTAR is able to design this rod string for
you. Also, it balances the steel design under the
fiberglass section (for two or more rod sections) so
that there is equal stress loading at the top of each
section as shown in Figure 4.11.
This Figure shows a fiberglass-steel rod string designed with RODSTAR. RODSTAR can design
tapered steel rod strings under the fiberglass section for any type of steel rod, including non-API
high strength rods, and Corods. If you want to
fine-tune a RODSTAR design, select to enter your
own rod string design by clicking on the manual
Figure 4.9 - Steel rod string design options
RODSTAR |33
Figure 4.10 - Fiberglass rod string design window
rod string entry icon. RODSTAR will show you
the current rod string design in memory as if
you entered it yourself. Then, you can make any
changes you want to the rod string without having
to reenter everything.
Also, you can have RODSTAR design the rod
string while calculating the pumping speed and
plunger size, to get the target production. However, because of the complexity of the calculations,
simultaneous use of all or most of RODSTAR’s
“smart” options will result in longer run times.
This is especially true if you also select to include
the effect of prime mover speed variation. Also,
depending on the case, RODSTAR’s run time
may be longer if you enter a target production that
is too large for the pumping system.
If you select only sinker bars on the bottom (without regular steel rods between the fiberglass and
sinker bar) then RODSTAR will calculate the
length of the sinker bar section for you. If you
select both sinker bars and a tapered steel design
between the sinker bars and the fiberglass rods,
then you must enter the length of the sinker bar (or
sinker rod) section. RODSTAR will determine the
Figure 4.11 - RODSTAR Designed Fiberglass-Steel Rod String
Figure 4.12 - Selecting rod grades in RODSTAR
length and diameters of the tapered steel portion
based on the maximum and minimum diameter
limits you enter.
RODSTAR may reject a steel rod diameter if it is
not needed. For example, if you asked RODSTAR
to design a rod string with fiberglass on top, a
tapered steel section under the fiberglass, and a
500 foot 1.5 inch sinker bar section on the bottom.
RODSTAR will determine the fiberglass diameter
and length you need, and the steel rod section and
tapers you need. If RODSTAR cannot balance the
steel rod string design because the 3/4’’ section is
not needed, it will not use any 3/4” rods.
Another interesting capability of RODSTAR is
that if you use continuous rods (Corod or Prorod)
instead of regular rods under the fiberglass, it may
skip a rod diameter, if it has to, in order to balance the rod string stress loading. This is not a bug.
Sometimes the program has to do this to successfully balance the steel portion of the rod string.
Entering Your Own (Manual) Rod String
This option is primarily used for entering rod
string data for an existing system you want to
simulate, or to modify a design that RODSTAR
itself came up with (when you select to have the
program design the rod string for you). This is
not a good option to use when you first design a
new system because it requires the most work and
experience.
When you select this option, you can enter data for
either steel or fiberglass rods as Figure 4.12 shows.
You can enter the number of rod sections, the service factor you want to use, and rod string data for
up to ten rod sections. For each section, you can
select the rod type or grade, diameter, and length.
For Fiberflex fiberglass rods you can also specify
the sucker rod length. In the deviated mode, for
each rod section, you may also enter the rod-tubing
friction coefficient, the type of rod guide, and
number of rod guides per rod. The rod-tubing friction is used to calculate the friction between the
rods and the tubing. This is different from the fluid
friction coefficient which is used to calculate the
friction between the rods and the fluid. In order
to enter the number of rod guides for each section,
you must activate this feature in Setup. There is
more information about this in section 3.3.3.
If you select one of the fiberglass manufacturers
listed on the drop down list next to the rod grade
input field, the program knows the weight per foot
and modulus of elasticity and will not prompt you
for them. The program warns you about rods that
RODSTAR |35
do not fit in the tubing. Also, it warns you
if the rod string length
is shorter or longer than
the pump depth. The
total length of the rod
string can be up to 50
feet shorter than the
pump depth. However,
it cannot be longer than
the pump depth. For
example, if the pump
depth is 5000 feet, you
can enter a rod string
that is between 4950
and 5000 feet. When
entering rod string data
for the first time, RODFigure 4.13 - Wellbore deviation entry window
STAR shows a default
length for the last rod
RODSTAR asks for confirmation whenever you
section equal to the
remove sections from the rod string, whether by
difference between the pump depth and the rod
using the Remove rod section button or by reducstring length you entered so far.
ing the number of rod sections.
Selecting the option to enter your own rod string
gives you maximum flexibility. However, it requires the most expertise to come up with a good
The meaning of the term “Sinker Bar” in RODSTAR
rod string design. You can use this option to select
In RODSTAR, the term “sinker bar” means a
different rod grade or manufacturer for each rod
steel rod that is made specifically to be used at
section. In general, this option allows you to enter
any rod string design, no matter how unusual. The the bottom of the rod string for weight such as 1
minimum length you can enter for any rod section
is 25’ (length of a single sucker rod).
When entering the rod string data manually,
RODSTAR allows you to add and remove rod sections from anywhere in the rod string, instead of
only at the bottom. The window has icons on the
left side for inserting a rod section, for removing
a rod section, or for moving a section up or down.
For example, if you want to remove a rod section,
first click on it and then click on the Delete Rod
rod section icon.
To add a rod section, click on an existing rod section and then click on the Insert/Add Rod Section icon. The new section will be added below
the selected section.
Figure 4.14 - Deviation entry icons
“Other” for the rod size.
4.2.5 Entering Wellbore Deviation Data
(Deviated Mode)
Figure 4.15 - Enter the number of entries
The deviated mode has an additional
input window for entering wellbore
deviation shown in Figure 4.13. Figure
Figure 4.16 - Entering deviation data manually
3/8”, 1½”, 1 5/8”, etc. The term “sinker rod” means
a regular rod such as a 1” or 7/8” rod that is
placed on the bottom of the rod string for
weight. For a 1” or 7/8” rod to be considered a
“sinker rod” it must be larger than the diameter of the rod above it.
When entering the rod string manually, make
sure you select “Sinker bars” in the list of rod
grades for sinker bars as shown in Figure
4.11. Do not select “Steel” rod type and then
Figure 4.17 - Import Wizard Options
RODSTAR |37
The easiest way to enter
the data is by using the
tab key to move from
field to field.
The “Add Entry” and
“Remove Entry” buttons can be used as
needed. At any time
during the data entry,
you can click on the
“Plot Survey” tab to see
a 3-D plot of the wellbore deviation entered
so far.
When inputting the
Azimuth, RODSTAR
recognizes both degrees (i.e. 340) and deFigure 4.18 - Step 1 of the Deviation Import Wizard
grees/minutes formats
4.14 explains the meaning of the icons shown on
(i.e. N20W or N20
the left side of this input window. You can activate 0W). As you continue to enter the deviation data,
these icons by clicking on them with the mouse.
the program calculates the numbers in the other
columns of the deviation input window. These
numbers are Dogleg severity, True Vertical Depth
Manual Entry of Deviation Survey
(TVD), North-South distance (N-S), and EastTo enter the deviation survey manually,
you need to know how
many deviation points
you have and the measured depth, inclination and azimuth of
each deviation survey
point.
Start by entering
the number of survey points as shown
in Figure 4.15. As
soon as you enter this
number, the program
will created the correct
number of rows for
you to enter the data as
Figure 4.19 - Step 2 of the Deviation Import Wizard
Figure 4.20 - Step 3 of the Deviation Import Wizard
Figure 4.21 - The last screen of the Deviation Import Wizard
RODSTAR |39
Figure 4.22 - The deviation survey after it was imported
West (E-W) distance in feet or meters.
Double-check your data to make sure you are entering the numbers correctly (especially if you see
dogleg severity numbers in red).
If RODSTAR is being used to analyze an existing well, the Deviation Survey Direction Toolbar
should be disabled. To disable this toolbar, click
the Setup icon, click the Defaults option, and uncheck the box labeled “Show Deviation Direction
Toolbar”. The Deviation Survey Direction Toolbar
is used to design a deviated well. While the toolbar
is active, the Azimuth is input in degrees and the
toolbar is utilized to designate a direction. Select
a direction first, then input the degree value. The
field will be automatically updated with the direction once the field is left.
NOTE: The NE direction is the default and will
not display any directional indicators (i.e. N20E or
N20 0E will be displayed as 20).
Using the Deviation Survey Import Wizard
You can use the deviation import wizard option to
import an Excel spreadsheet or CSV file with deviation data, or to import a deviation survey from a
Theta software file which contains deviation data.
The two Theta file types that contain direction
survey data are RODSTAR files (extension “.rsdx”)
and XDIAG-D files (extension “.xddx”).
To Import a Deviation Survey, click the “Import
Wizard” button. Using the Import Wizard Dialog window, select the source of your Deviation
Survey. In this example we are using a Microsoft
as shown in Figure 4.18.
Step 2 allows you to select the Workbook and
Spreadsheet to use in cases where there are more
than one in the Excel file as shown in Figure 4.19.
Step 3 automatically locates the columns in the
spreadsheet where the values are stored for the
Measured Depth, Inclination, and Azimuth as
The next step loads the data and then finishes as
Figure 4.23 - The 3-D Plot of the deviation Survey
Excel spreadsheet.
Step 1 prompts you to select the file to be imported
Click “Done” and view the imported deviation
survey data as shown in Figure 4.22.
RODSTAR |41
Figure 4.24 - Pumping unit manufacturer list
Please keep in mind that for program to be able to
load the deviation data from an Excel spreadsheet,
it must see three columns with the deviation data.
These columns need to be labeled as follows:
“Measured Depth (ft)” or “MD (ft)”, or “MD (m)”
“Inclination”
“Azimuth”
Clicking the “Plot Survey” tab on the right side
of the window will display the Deviation Plot as
shown in Figure 4.23. From this screen, you can
rotate the plot to better understand and visualize
the wellbore deviation, you can zoom in, etc.
4.2.6 Entering Pumping Unit Data
The pumping unit input screen allows you to select
a pumping unit from the database that comes with
RODSTAR, or from your measured pumping unit
database (if you entered your own pumping unit
dimensions in Setup).
Another option is to enter a pumping unit ID.
The pumping unit ID is a unique string of letters
and numbers. RODSTAR displays the pumping
unit ID along with other unit information after
you select a unit. If you make a note of this unit
ID (in the well file for example), you can use it
to specify the pumping unit instead of having to
select it from the list. This is a unique ID for each
pumping unit in the program’s database.
Selecting a pumping unit manufacturer
RODSTAR allows you to easily select a pumping
unit manufacturer and unit size with drop-down
list boxes. To display the menu with all pumping
unit types available, click on the drop arrow next
to the “Manufacturer” field (see Figure 4.24).
This is a scrollable list of all units in the program’s
database in alphabetical order. You can go to the
}. You can jump to
the bottom of the list by pressing ~. You can
top of the list by pressing
also move up or down by pressing O (Page up)
or N (Page Down). A convenient way to move
Figure 4.25 - Measured pumping unit list
through the list is to press the first letter of the
unit name you want to use. For example, to locate
the National “E” Series pumping unit entry, you
can press n and the highlight bar will jump to
the first name in the list that starts with N. Then
simply click on the National “E” Series entry. At
the top of the list of pumping unit manufacturers is the item (Measured pumping units). This
option allows you to select a unit for which you
entered geometric data in Setup.
When you select the (Measured pumping units)
option, RODSTAR will display a list that only
shows the measured pumping units, as Figure 4.25
shows.
As Figures 4.24 and 4.25 show, there is a check
box that allows you to use the custom pumping
unit list instead of the main pumping unit list. If
you check this option, before you select a unit,
the Manufacturer list will show a shorter list that
contains only the manufacturers you selected in
Setup in your custom unit list as shown in Figure
4.26. When the “Use custom pumping unit list”
option is checked, when you select a pumping unit,
you will see a short list containing only the unit
sizes you selected for your customized list for this
manufacturer.
After you select a manufacturer you can use the
same procedure to select the unit size you want
from the pumping unit drop-down list box . You
can move through this list the same way as with
the pumping unit manufacturer selection menu.
The pumping units on this menu are ordered from
largest to smallest stroke length, gearbox size, and
structure size. However, if the window shows the
pumping unit name (for old units) the units are
listed alphabetically.
When you enter a unit, the Unit ID, the program
automatically displays the unit that the ID corresponds to. RODSTAR displays the information
necessary for you to correctly identify your unit.
For example, for American conventional units you
will see that certain unit sizes appear more than
once on the selection list. However, they have different cranks.
RODSTAR |43
Figure 4.26 - The custom pumping unit list
How to add units to the custom pumping unit list
You can use the “Use custom pumping unit list”
check box to add units from the main list to your
custom list. For example, if you run across a pumping unit that is not in your custom list yet, clear
the “Use custom pumping unit list” check box so
that you can use the general pumping unit list.
After you select the pumping unit then click on
the “Use custom pumping unit list” check box.
RODSTAR asks if you want to add this pumping
unit to the custom pumping unit database. Select
Yes to add this unit to your custom list. The program will add this unit to the custom list and also
switches to the custom list.
This option only allows you to add units to your
custom list without having to do it from Setup. To
remove units from your custom list or to add more
than one unit, go to the setup window and customize the list of units as described earlier in this
manual.
Selecting to enter a pumping unit ID
The unit ID option is the fastest way to enter
pumping unit information if you already know
the pumping unit ID for your unit. You can see
the pumping unit ID on the pumping unit entry
window after you select a unit. Once you locate
your unit, you can make a note of its ID in the well
file. Then, the next time you want to use this unit,
you can select to enter its ID. For example, for a
Lufkin Mark II M-456-305-144, the unit ID is
ML32.
To identify some units correctly, it is necessary
to know the crank number since they may have
the same API designation but different geometric
dimensions depending on crank number (primarily
units made by American International Manufacturing Company).
TIP: If your unit is not listed in RODSTAR
and you do not have the unit dimensions, then
use a unit that is closest to it. As long as you use
the same unit geometry and a unit with the same
Figure 4.27 - RODSTAR recommends a unit size based on target production
stroke length and gearbox rating, the results should
be close to actual as long as the pumping unit is
the same unit type as the one you selected.
to use uncommon unit geometries such as the
Rotaflex, then this recommendation may not be as
useful. RODSTAR makes this recommendation
without running through the predictive calculaIf after you enter a pumping unit ID RODSTAR
displays “The pumping ID you entered is not valid” tions. Therefore, it may not necessarily recommend
the best pumping unit size for your application.
this means that ID you entered is not recognized
However, in most cases it should be pretty close to
by RODSTAR. This can happen for two reasons:
the size you need.
1) You entered the wrong ID such as R0 (which
There are other important factors that you must
does not exist), or CL901 instead of CL91.
consider when deciding what unit size you need.
2) You have erased the pumping unit file by acciThese include: available used pumping units, exdent, or the pumping unit files are not in the same pected changes in well conditions, desired pumpdirectory as the program.
ing speed, etc. When you enter data for a case
for the first time and you are at the pumping unit
RODSTAR Recommended unit size
selection screen, RODSTAR will not only display
If you enter a target production instead of pumpthe recommended unit size, but will automatically
ing speed, RODSTAR will display a recommended
select the unit closest to the recommended size
pumping unit size to help you select a pumping
from the available list. If you do not want to use
unit. This recommendation can be very helpful
the unit recommended by RODSTAR then select
if you are designing a new pumping system and
another one. The recommended unit size is a push
must decide what size unit you need. RODSTAR
button, as shown in Figure 4.27. So, whenever you
recommends sizes that are closest to conventional
want to return to the pumping unit size recomunits as Figure 4.27 shows. Therefore, if you plan
mended by RODSTAR, just click the button and
RODSTAR will automatically select the unit size
that is closest to the recommended size.
In general, the size recommended by RODSTAR
will be close to the minimum required conventional
unit. RODSTAR recommends only the API unit
size. You must decide what manufacturer and
unit type to use. If you select a conventional unit
and RODSTAR predicts that the gearbox will
be overloaded, then try using the same size Mark
II or enhanced geometry unit. In some cases you
may be able to use a smaller unit by selecting a
geometry that is better suited for your application.
There are several factors that determine what unit
is best. They include, cost, gearbox loading, system
efficiency, rod compression, minimum polished rod
load (indicates separation of the polished rod from
the carrier bar if close to zero), etc.
Selecting crank hole number and crank rotation
After you select a pumping unit you must select
the crank hole number, and the direction of rotation with the well to the right (if you are using a
unit that can rotate either way). For units with a
required direction of rotation, like the Mark II ,
Torqmaster, Lufkin Reverse Mark, or American
Producer II, the program will not allow you to
change crank rotation. For units that can rotate
either clockwise or counterclockwise, RODSTAR
defaults to the direction of rotation that will usually give the lowest torque. However, this default
direction of rotation may not always be ideal for
your system design. To find out for sure which
rotation is best for your system you must make
two runs: one with clockwise crank rotation and
one counterclockwise. Then look at the effect of
rotation on gearbox torque, system efficiency, rod
loading, etc.
RODSTAR |45
in RODSTAR’s database, you can enter your own
pumping unit dimensions. To enter the data in the
program you have to first access the setup screen
of RODSTAR (click on fourth button on toolbar).
Then, double-click on “Pumping Unit Options”
tab and select “Measured Pumping Unit List” as
explained in section 3.3.5 in this manual. Then,
select to add a new unit to enter data for a new
pumping unit.
The data you must enter consists of geometric
dimensions as defined in the API 11E publication.
You can get these dimensions from the pumping
unit manufacturer or measure them yourself. Or,
you may be able to find most of the dimensions
you need from catalogs or blue prints. For old units
without an API designation on their nameplate,
you may be able to put together an equivalent API
designation. Look at the gearbox nameplate for the
gearbox rating in thousands of in-lbs. Measure the
stroke length, and try to decipher additional information from the unit’s nameplate for the structure
rating, stroke length, and structural unbalance.
If the nameplate is legible then write down the
unit’s serial number or order number. If the unit’s
manufacturer is still in business, you may be able
to get the data you need from the serial number
or order number. For help in locating dimensional
data for pumping units not in the manual call
Theta Oilfield Services, Inc..
RODSTAR allows you to enter data for Conventional, Mark II, Air Balanced, Enhanced Geom-
Entering your own pumping unit data
If the pumping unit you want to simulate is not
Figure 4.28 - Conventional/Enhanced
offset angle in degrees. For enhanced geometry
units the crank offset angle must be negative. In
the software, Beam Balanced units are balanced
using structural unbalance. This is because they are
balanced using beam weights as opposed to crank
weights. The API spec. 11E defines the above
dimensions as follows:
Figure 4.29 - Beam Balanced
etry, or Long Stroke units. When you enter your
own pumping unit dimensions, RODSTAR calculates and displays the stroke length based on the
dimensions you enter. For all pumping unit types
you must first enter the name of the manufacturer,
the unit name or model number, the gearbox rating in thousands of inch pounds, the structure
rating in hundreds of pounds, and the maximum
stroke length in inches. From these numbers
RODSTAR puts together the API pumping unit
designation. The API pumping unit designation is
a standard way of describing the size and capacity
of pumping units as the following example explains:
The first number is the gearbox rating in thousand
inch-pounds. In this example the gearbox rating is
320,000 inch-lbs. The second number is the structure rating in hundreds of pounds. In this case the
structural rating is 256. This means that to avoid
overloading the structure of the unit, polished rod
load must not exceed 25,600 lbs. The last number
shows the maximum stroke length of the unit in
inches (100 inches in this case). Following is an
explanation of the rest of the data needed for each
unit type:
Conventional, Enhanced and Beam Balanced
Geometry Pumping Unit Data
For these units you must enter pumping unit
dimensions R, A, C, I, P, and K in inches, the
structural unbalance in pounds, and the crank
Figure 4.30 - Mark II
Dimension:
Description:
R
Radius of the crank (inches)
A
Distance from the centerline of the
saddle bearing to the centerline of
the polished rod (inches)
C
saddle bearing to the centerline of
the polished rod (inches)
I
Horizontal distance from the
centerline of the saddle bearing
to the centerline of the crankshaft
(inches)
P
Effective length of the pitman
arm, in inches (from the center of
the equalizer bearing to the center
of the crank-pin bearing)
K
RODSTAR |47
Distance from the center of the
crankshaft to the center of the
saddle bearing (inches). Sometimes, instead of the K dimension, pumping unit manufacturers
supply data for dimensions H and
G instead (described below). From
these dimensions and dimension I
(defined above) you can calculate
K
Sampson Post bearing (inches)
Height from the center of the
saddle bearing to the bottom of
the base beams (inches)
crank shaft to the bottom of the
base beams (inches)
H
G
2
H
G
2
)
K as follows: K= ( H-G + I
saddle bearing to the bottom of
the base beams (inches)
base beams (inches)
Air Balanced Pumping Unit Data
For these units you must also enter pumping unit
dimensions R, A, C, I, P, and K in inches. In addition, you need data for M, S and V0.
Mark II Pumping Unit Data
For Mark II units you must also enter pumping
unit dimensions R, A, C, I, P, and K in inches,
the structural unbalance in pounds, and the crank
offset angle in degrees. This angle is positive for
Mark II units. The API spec. 11E defines the
above dimensions as follows:
Dimension:
R
A
C
I
P
Description:
Sampson Post bearing to the centerline of the polished rod (inches)
Sampson Post bearing to the center of the equalizer (or cross yoke)
bearing (inches)
Horizontal distance between the
centerline of the Sampson Post
bearing and the centerline of the
crankshaft (inches)
the equalizer (or cross yoke) bearing to the center of the crank-pin
bearing)
Figure 4.31 - Air Balanced
The API spec. 11E defines the above dimensions
as follows:
Dimension:
R
Description:
A
C
I
P
K
M
S
V0
Sampson Post bearing to the centerline of the polished rod (inches)
Distance from the centerline of
the Sampson Post bearing to the
center of the equalizer bearing
(inches)
Horizontal distance between the
centerline of the Sampson Post
bearing and the centerline of the
crankshaft (inches)
the equalizer bearing to the center
of the crank-pin bearing)
Sampson Post bearing (inches).
Geometry constant (in2). It is the
distance from the Sampson Post
bearing to air tank bearing (distance X in Figure 2.3) multiplied
by the area of the piston in the air
cylinder divided by dimension A
or: X*Ap/A, where Ap is the area
of the air cylinder piston in square
inches.
Pressure in the air counterbalance cylinder required to offset
the weight of the walking beam,
horsehead, equalizer, pitman arms,
etc. (psig).
Minimum air volume between the
plunger and cylinder at the bottom
of the stroke (in3).
For these units you must enter pumping unit
dimensions R, D, I, and K in inches and the crank
offset angle in degrees. The crank offset angle is
negative for these units. The structural unbalance
for belted low profile units is negligible and therefore zero because, when you disconnect the pitman
arms from the belt, there is no counterbalance
from the belt and bridal assembly. We define the
above dimensions as follows:
Dimension:
R
D
I
K
Description:
Diameter of the drum (inches)
which holds the belt
Horizontal distance from the
centerline of the saddle bearing
to the centerline of the crankshaft
(inches)
drum bearing (inches). Sometimes,
instead of the K dimension, pumping unit manufacturers supply data
for dimensions H and G instead
(described below). From these dimensions and dimension I (defined
above) you can calculate K
2
H
G
2
)
as follows: K= ( H-G + I
drum bearing to the bottom of the
base beams (inches)
base beams (inches)
Long Stroke Pumping Unit Data
Figure 4.32 - Belted Low Profile
Belted Low Profile Pumping Unit Data
For these units you must enter the sprocket
diameter (D), the centerline distance between
the top and bottom sprockets (distance C), the
pitman arm length (P) if one exists (usually this
is zero), and the top drum diameter ratio (usually
equal to 1). You can see a diagram of the dimensional data you need by pressing F1 in any input
RODSTAR |49
Figure 4.34 - Definition of structural unbalance
Tip: To predict energy consumption more accurately for hydraulic units using the long stroke
pumping unit model, input a pitman arm length of
zero and a drum diameter ratio of 2.
Figure 4.33 - Dimensions for long stroke units
field, or you can take a look at Figure 4.33.
You can also use this pumping unit model to
simulate any non-beam pumping unit with a
long, slow stroke. You can do this by entering
data that will produce the same stroke length as
the unit you want to model. The stroke length of a
long stroke unit is given by:
Stroke = C + D
For example, to simulate a hydraulic pumping unit
with a stroke length of 200 inches, you can enter a
sprocket diameter (D) of 20 inches and a centerline
distance between sprockets equal to 180 inches.
If you use this approach to design a system with a
hydraulic unit then the torque calculations, energy
consumption, and other results that depend on
torque will be incorrect or meaningless. However,
the predicted polished rod dynamometer card,
polished rod horsepower, stress analysis, etc. will
be valid. This technique can be used as long as the
upstroke and downstroke polished rod velocities
of the hydraulic or long stroke unit you want to
simulate are approximately equal.
Another thing to keep in mind is that even though
the combination of C and D dimensions determines the stroke length of long stroke units, the
ratio of C/D determines the acceleration and deceleration of the polished rod. For the long stroke
geometry shown in Figure 4.33, when the connection point between the belt and the chain touches
the sprocket, the polished rod speed changes
(accelerates or decelerates). When the connection
point leaves the sprocket (C section in Figure 4.33)
the speed is constant. Therefore, different combinations of C and D dimensions may be needed
to correctly simulate the polished rod motion of a
Figure 4.35 - Definition of crank offset angle
hydraulic pumping unit.
Definition of Structural Unbalance
Structural unbalance is a term used for pumping
units with walking beams. It is defined in API
11E as the force you need at the polished rod to
hold the walking beam horizontal with the pitman
arms disconnected from the crank pins. This force
is positive when acting down and negative when
acting up. See Figure 4.34 for a visual explanation
of structural unbalance. Structural unbalance for
conventional units can be either positive or negative. For Mark II units it is always negative. If you
do not know the structural unbalance for the unit
you want to simulate then enter zero. In most cases
the structural unbalance will not affect the results
significantly (especially for Conventional geometry
units).
Definition of Crank Offset Angle
The crank offset angle (or crank phase angle) is
the angle between a line through the crank holes
and a line through the counterweight arm. Figure
4.35 shows how the crank offset angle is defined.
RODSTAR expects a positive crank offset angle
for Mark II units and a negative one for enhanced
geometry units such as the Torqmaster, Lufkin
Reverse Mark, or American Producer II. For
conventional pumping units the crank offset angle
is zero.
Entering Counterbalance Information
After you select a pumping unit or enter your own
pumping unit data, the crank hole number, and
direction of rotation, you must enter counterbalance information.
Entering an existing maximum counterbalance
moment allows you to simulate an existing system to find out if the unit is overloaded or out of
balance. If you only want to find the maximum
counterbalance moment required to balance the
unit (which is usually the case for new designs)
then click on the “Unknown” check box and
RODSTAR will calculate it for you.
For beam pumping units except for air balanced,
you can enter a maximum counterbalance moment
in thousand inch-lbs. RODSTAR also gives you
the option to import the maximum counterbalance
moment from a XBAL file or from the clipboard.
If you ran XBAL before running RODSTAR,
then the value of the existing maximum counterbalance moment will be in the clipboard. Then, as
soon as you click on the Use XBAL information
button, RODSTAR will allow you to use the value
exported by XBAL or to read a XBAL file from
disk.
For air balanced units you must enter the air cylinder pressure in psig at the bottom of the stroke.
For long stroke units you must enter the counterbalance weight in thousands of pounds. For these
units, the option to read a XBAL file is disabled
since it does not apply.
If you enter existing counterbalance data, RODSTAR calculates and displays the permissible
load diagram for existing conditions. Also, the
recommended prime mover size and overall system
efficiency will be for the existing conditions. If
you select “unknown” for maximum counterbalance moment then RODSTAR calculates all these
numbers and the permissible load diagram for balanced conditions only.
The range of allowable counterweight is different for different Rotaflex units. RODSTAR takes
this into account when validating your entry for
counterbalance weight. For example, the minimum counterweight possible for the 1200 model
is 13,500 lbs. Therefore, if you try to enter a counterweight that is less than 13.5 M lbs, (M =thousands) RODSTAR will warn you that the counterweight for this unit must be between 13.5 and 32.5
M lbs.
Changing Structural Unbalance
In some cases, when the pumping unit is significantly oversized for the downhole equipment, you
RODSTAR |51
Figure 4.36 - Entering motor information
may have to add counterweights on the walking
beam next to the horsehead to balance the unit.
This changes the structural unbalance from the
catalog value. RODSTAR allows you to change
the structural unbalance even when you select a
pumping unit from the program’s database.
The structural unbalance field can also be used to
simulate beam balanced units. By changing the
value of the structural unbalance, you can figure
out how much weight you need to add or remove
from the walking beam to balance a beam balanced unit.
4.2.7 Entering Motor Information and Energy Cost
RODSTAR can simulate NEMA D or ultra high
slip motors and calculates power consumption
from actual motor efficiency curves. The program
uses the electricity cost you enter to predict the
monthly electricity bill, $/bbl fluid, and $/bbl oil
(based on water cut). RODSTAR defaults to the
cost number you specify in Setup. The $ symbol
here is meant to represent currency (not just US
dollars). As Figure 4.36 shows, under the electricity cost input box there are option buttons that you
can use to select the power meter type. You have
two options: Detent, or Non-detent. A Detent
KWH meter can rotate only in one direction. A
ratchet prevents it from turning the other way.
Therefore, if your unit is generating electricity, you
do not get credit for it. The non-detent meter can
rotate either way and so it credits you for electricity
the pumping unit generates.
Prime mover type selection
Using drop-down list boxes you can select the
motor type you want to simulate. RODSTAR has
motor performance and efficiency data for NEMA
D, Sargent Ultra High Slip, Reliance Ultra High
Slip motors, and Rotaflex Multi-HP NEMA
C motors. If you select a NEMA D motor you
can enter a motor size, or you can choose to have
RODSTAR recommend a NEMA D motor for
you. If you select an ultra high slip motor then you
must select the motor size and torque mode. If you
select a motor size or mode that is too small for
the well conditions then RODSTAR will display
a warning message and will give you the option to
change your data.
RODSTAR warns you if you select an ultra-highslip motor when you have selected an air-balanced
or long stroke pumping unit. These units have little
or no rotating moment of inertia, so using an ultrahigh-slip motor does not result in any significant
differences in the calculations. Therefore, for these
units, do not select an ultra high slip motor or to
include speed variation effects.
If you select a NEMA D motor type for a new
case, or switch from an ultra-high-slip motor to
a NEMA D motor, RODSTAR automatically
selects the option to recommend the motor size.
Motor speed variation
The option to include the effect of motor speed
variation is only available for conventional, enhanced geometry, and Mark II units. Inertia effects are negligible for long stroke and air balanced
units.
If you select not to include speed variation effects
then RODSTAR assumes constant prime mover
speed and will not model the effect of pumping
unit inertia. If you choose to include speed variation then RODSTAR gives you the option to enter
a percent speed variation or have the program
calculate the speed variation for your prime mover.
Pumping unit moments of inertia
If you select to include the effect of motor speed
variation then you can enter a rotating moment
of inertia in lbs-ft2, or have the program estimate
this number for you. For the articulating moment
of inertia RODSTAR defaults to a number that
is either the actual articulating moment of inertia
supplied by the pumping unit manufacturer, or
an estimate based on unit size. Therefore, unless
you have an even more accurate number for the
articulating moment of inertia, it is recommended
that you use the default number displayed by the
program.
For more accurate results, have RODSTAR calculate the prime mover speed variation. However,
you can also enter a speed variation value if desired. If you select to enter speed variation, RODSTAR shows a default value of 8% which corresponds to a recommended average speed variation
for NEMA D motors. You can get more conservative results by entering a speed variation that is
less than the maximum expected speed variation
for your prime mover. Selecting to include prime
mover speed variation will approximately double
RODSTAR’s run time.
What is moment of inertia?
Although this manual is not intended to teach
engineering or physics, it is important to briefly
explain moment of inertia and how it can affect
RODSTAR’s results. The mass moment of inertia
of a body is a measure of its resistance to acceleration. In other words, the higher the moment of
inertia of a body, the more difficult it is to quickly
speed it up or slow it down.
The rotating and articulating moments of inertia
are important in accurately simulating the behavior
of the pumping unit and in calculating net gearbox
torque when you use a high speed variation prime
mover. The rotating moment of inertia that RODSTAR needs is the total rotating moment of inertia. This includes the individual rotating moments
of inertia of the cranks and counterweights about
the slow speed shaft of the pumping unit, the total
gear reducer inertia, and the motor rotor inertia.
The articulating moment of inertia of the pumping
unit around the saddle bearing includes the inertia
of the walking beam, horsehead, and pitman arms.
As mentioned above, you can either enter a rotating moment of inertia, or you can have RODSTAR estimate it for you. To calculate accurately
the rotating moment of inertia you must have
moment of inertia data for the cranks and counterweights, gearbox, motor rotor, etc. Also, the
rotating moment of inertia depends on the position
of the counterweights on the cranks. Since this
data may not be known, it is recommended that
you let RODSTAR estimate the rotating moment
of inertia for you.
Since the articulating moment of inertia depends
on the walking beam size, horsehead and pitman
arms, it is a fixed number for any given pumping
unit. Therefore, it is easier to calculate than the
rotating moment of inertia. RODSTAR’s pumping unit data base contains accurate articulating
moment of inertia values that were either obtained
from unit manufacturers, or were estimated based
on unit size. The articulating moment of inertia
from the pumping unit database appears as the
default number when the program prompts you for
the articulating moment of inertia.
Including speed variation and moments of inertia
will usually result in lower predicted peak gearbox
torque, lower peak polished rod load, and higher
minimum polished rod load. This is because a
high speed variation prime mover slows down as
the torque on it increases. The rotational inertia of
cranks and counterweights causes a release of energy that lowers the torque the gearbox must supply.
The articulating inertia adds torque to the gearbox
since it opposes the acceleration of the walking
beam and horsehead. However, the effect of the
articulating moment of inertia is usually small
compared to the effect of the rotating moment
of inertia. When the prime mover slows down in
response to high torque, it causes the polished rod
to slow down as well. This results in lower dynamic
forces and therefore lower peak polished rod load.
RODSTAR |53
54 | Changing, Loading and Saving Data
5
Changing, Loading and Saving Data
5.1 Visual Input
Figure 5.1 shows RODSTAR’s “visual” input facility that makes it easy to locate a system parameter
you want to change. As you are entering the data
for a new case, or after you have loaded a case from
disk, the visual input window can be displayed by
clicking on the Visual Input button on the toolbar.
This shows an interactive picture of the pumping
system.
then choosing Save As... This brings up a standard Windows dialog box that allows you to save
your file with the file name you want. RODSTAR
shows the default file name it creates from the well
name and by adding an “.RSVX” file name extension for vertical cases or “.RSDX” for deviated
cases. If you enter data for a case in the deviated
As you move your mouse over the picture of the
system, tool tips appear naming various parts of
the system. Whenever a tool tip is showing, you
can right-click with the mouse to get a pop-up
menu listing input variables associated with that
part of the system. This visual way of changing
data is more useful when you are changing data
in existing files or when you are making “what
if...” runs. If you are entering a case from scratch,
menu items that correspond to data you haven’t yet
entered will be disabled.
Left-clicking when a tool tip is displayed opens the
data entry window associated with the part of the
system you clicked on. Another way to change data
is to click on the “Alphabetical list…” button at
the bottom of the visual input window. This brings
ups an alphabetical listing of all variables you can
change. You can locate the variable you want to
change by scrolling down using the mouse.
5.2 Storing Data Files
After you finish entering data for a system, you can
save the data to disk by clicking on the Quick Save
button on the toolbar (third from left with diskette
icon), or by selecting File from the menu bar and
Figure 5.1 - RODSTAR’s Visual Input window
RODSTAR |55
mode but do not enter deviation survey data, the
program will save the file with an extension of
“.RSVX” instead of “.RSDX”. You can change the
file name by typing over it, but you cannot change
the file name extension. When you type your own
file name, you do not have to type the file name
extension. RODSTAR automatically adds this
extension for you.
You do not have to store your data every time
you make a change. It is recommended that you
save the original data and then wait until you get
a good design before storing data to disk. After
saving data once, RODSTAR makes it very easy
to update the file with the data in memory with a
single mouse click on the Quick Save button on
the toolbar.
If you save your data after running RODSTAR
and the output is displayed on screen, then RODSTAR saves both the input and output in the file.
This is advantageous because once you save the
output then you can view and print the output
without having to rerun the case.
5.3 Running and Viewing the
Output
After you enter all your data and you press the
Next Screen button from the motor information
window, the Run button on the toolbar becomes
active. To run the program simply click on the
Run button on the toolbar (the dynamometer card
icon to the right of the right arrow icon). Another
way to run the program is to click on Run on the
menu bar. After RODSTAR runs, it displays the
output report, as Figure 5.2 shows. At the bottom
of this screen there are buttons that allow you to
view the dynamometer, torque, or IPR plots and
the report. When you select to see the dynamom-
Figure 5.2 - Summary output report - upper half
Figure 5.3 - Summary output report - lower half
eter plots, you can select to animate then surface
and downhole pump cards.
To look at different parts of the output you can
click the appropriate buttons at the bottom of the
screen (Dynamometer, Torque, IPR Plot, Dev.
Plots when using RODSTAR, or Report). When
you click on Report, you can scroll up or down
with the mouse, or you can click and drag on the
report itself. Figure 5.3 shows the bottom section
of the summary report. The summary report looks
exactly the same as the printed report.
If you have XBAL on your computer, you can have
RODSTAR export the balanced maximum counterbalance moment it calculates to XBAL. You
can do this any time the calculations have been
run (whether or not you are actually viewing them)
by clicking on the Export CBM button on the
toolbar (
mum energy consumption.
The most common way to balance a unit is for
minimum torque. However, if the gearbox is not
overloaded, you may want to balance the unit for
minimum energy consumption instead.
After viewing the output you can decide which
value of balanced counterbalance moment you
want to export to XBAL (so that XBAL can
calculate the counterweight positions required to
balance the unit). When you click on the Export
CBM... button, RODSTAR displays the window
shown in Figure 5.4 (if there are two possible ways
to balance the unit). Click on the option you want
and click on the OK button. RODSTAR confirms
that the value of the maximum counterbalance
moment has been exported by displaying the message box shown in Figure 5.5.
).
RODSTAR can calculate two possible ways to
balance a unit: for minimum torque, or for mini-
5.3.1 Saving the output
RODSTAR |57
to run in batch, click on the first
file and then, while pressing S,
click on the last file in the list. Or,
you can click on the first file and
then drag the mouse to highlight
all the files you want to run (it must
be a continuous group). To select
individual files, click on the files you
want to select while pressing C.
The selected files are highlighted
as Figure 5.6 shows. When you are
done selecting files, click OK.
Figure 5.4 - Exporting the maximum CB moment
If you save the file while the output is being displayed on the screen, RODSTAR saves the output
along with the input in the same file. Then, you
can load a file with output and you can display and
print the output without
having to rerun the program. To save the output,
click on the quick save
icon on the tool bar, or
select File on the menu
bar and then select Save
As..
When you load a file that
has output saved, the
program will tell you that
output results are available on the status bar (at
the bottom of the RODSTAR window).
At this point, RODSTAR will display the option
box in Figure 5.7 asking you to choose the options
Figure 5.5 - Maximum CB moment exported
5.3.2 Running in Batch Mode
You can run more than one case at a time by selecting to run two or more files in batch mode. The
batch mode starts automatically when you select
to load more than one file. This capability allows
you to make an unlimited number of RODSTAR
runs automatically, and without you having to be
at the computer. RODSTAR even allows you to
schedule the batch run to start at any time (from
the Setup window).
To start the batch, select to open a file (either by
clicking the Open File toolbar button, or by selecting Open… from the File menu). This brings up
the open file dialog box. To select a group of files
you want for the batch run. The first option causes
RODSTAR to create printouts for all the files
it runs. This option is unselected by default. The
second option causes RODSTAR to create a summary spreadsheet file for all the cases it runs. The
option to view the spreadsheet in Excel means that
once the cases are processed and the spreadsheet is
created, RODSTAR will automatically load Excel
and display the results for you.
The next option allows you to save the output
reports in PDF format. The reports will be saved
in the same folder as the RODSTAR files are currently stored. For example, if the RODSTAR files
that you are running in batch are located at “C:\
THETA”, then you will find the PDF files of the
output reports in the same folder after the batch
run.
STAR uses the default
spreadsheet format that
comes with RODSTAR
and contains the most
common system design
comparison variables.
Figure 5.6 - Selecting files for a batch run
The last option allows you to specify whether you
want RODSTAR to rerun cases with saved output
or not.
If you do not select the option “View spreadsheet
in Excel” when you click on “Proceed”, RODSTAR asks you for Excel file name as shown in
Figure 5.8. Otherwise, if you select to view
spreadsheet in Excel, RODSTAR starts running
in batch immediately.
Creating a summary spreadsheet is very useful
because it allows you to summarize many runs
in a very concise way. After the results are in a
spreadsheet file, you can plot one variable versus
another, you can sort the spreadsheet columns by
rod string cost, system efficiency, energy cost per
barrel of oil, etc. There is no limit to what you
can do with the results.
The spreadsheets that RODSTAR create summarize the results of all the runs and loads it directly
into Excel. Under the Setup window you can “design” and save an unlimited number of spreadsheet
formats. If you do not specify a spreadsheet format
before running many cases in batch mode, ROD-
The option “Don’t rerun cases with saved
output” allows you to
create different summary
spreadsheet files with the
same set of RODSTAR
files. When you select
this option RODSTAR
runs very fast in batch
because all it has to do
is extract the calculated
values that have already
been saved in the RODSTAR files and enter
them in the spreadsheet.
When RODSTAR starts
to run the files you selected, it displays a batch run
log window such as that shown in Figure 5.9 that
shows the number of files you selected, the number
of runs that have been completed so far, and the
overall percent completion. RODSTAR shows the
Figure 5.7 - Batch run options
name of each file that it runs. RODSTAR prints
warnings or errors after the name line while running each case. After each new run is complete,
the program prints “** Run Complete **”.
This is a useful record of the cases that RODSTAR ran and any warning or errors generated
while running them. You can cancel a batch run
RODSTAR |59
at any time
by clicking
on “Cancel”.
The program
will stop after
it finishes
running the
current case
and it will
display a message box that
says: “The
batch run was
canceled.”
overnight.
5.4
We recommend printing the batch
run log,
especially
when running
Figure 5.8 - Selecting a spreadsheet file to create
many RODSTAR cases.
The batch run log shows what files you ran, and
any errors or warnings for each case. To view an
output report of one of
your cases, double click
the blue title bar which
displays the directory
and the file name. To
return to the batch run
log click the “Close”
button on the bottom of
the output window.
Loading Data from Disk
The batch run capability is especially useful
for the deviated mode
Figure 5.9 - A batch run log
because it requires more
calculations than the
vertical mode. Because
After you enter data and store a file you can easily
of the complexity of the calculations for deviated
modify it by loading it back in memory. Also, you
wellbores, RODSTAR runs may rake a minute
can load a file with saved output and view or print
or two to run in most cases and sometimes even
longer. Therefore, using the batch process can save the output results without having to rerun a case.
You can do this by:
you from having to wait for each case to run. You
can have your case execute while at lunch or even
- Clicking on the Open button on the toolbar (sec-
ond from left).
- Clicking on File on
the Menu bar and then
on Open, or by pressing
C+ o.
Also, RODSTAR keeps
track of up to nine of
the most recent files
you saved or loaded and
allows you to quickly
load any of them. To see
a list of these files click
on the drop-down icon
between the file open
and file save icons on the
tool bar and then click
on the file you want to
load. Or, you can click
on File from the menu
bar and select “Recent
Files”
Figure 5.10 - Selecting a file to open
If there is data in memory, RODSTAR will warn
you that loading new data will erase the existing
data in memory. This alerts you and helps prevent accidental loss of your data before you have a
chance to save it.
RODSTAR has a powerful and easy-to-use file
management system. When you select to load data
from disk, RODSTAR displays the current path
and a list of files in the current directory in alphabetical order. Also, RODSTAR allows you to read
RODDIAG files, XDIAG files, and even older
RODSTAR files. RODSTAR displays a list of the
file type you selected in the current directory as
the Figure 5.10 shows.
To load one of these files, double click on it, or
click on it once and then click on OK. If the file
you want is not in the current directory, you can
easily move to any directory on any drive in your
system since this window also lists sub directories,
and system drives.
If your current directory contains many RODSTAR files, it may be faster to press the first char-
acter of the file you are looking for. For example,
if you are looking for well name “PR101.RSVX”,
click in the list once, and then press p and the
program will jump to the first file in the list that
starts with “P.”
5.4.1 Viewing Previously Saved Output
When you load a file that contains output you
can display the output without having to rerun
the case. When you load a case that contains
input data only (no output results were saved),
RODSTAR displays the first input window (well
information). Also, the report and print icons on
the toolbar are not available. However, when you
load a file that contains both input and output,
RODSTAR does not open any input windows.
The status bar at the bottom of the screen shows a
message like the following:
“Successfully loaded file: C:\Theta\RODSTAR
cases\special cases\abc#1.rsvx (output results are
available).”
Also, the report and print icons on the tool bar are
active. To see the output without having to re-run
Figure 5.11 - Minimized input windows
the case, click on the report icon on the tool bar.
To print the output, click on the printer icon (next
to the email icon).
5.5 Manipulating Input Windows
RODSTAR is a standard Microsoft Windows application and it allows you to manipulate the input
windows several different ways. After entering
data for all the input windows, or after you load
a file from disk, you can display one window at a
time, you can open all windows, or you can arrange them any way you want as explained below:
♦♦
After entering data for a case or after loading a file from disk, click on each window’s icon on
the toolbar. This loads all input windows.
♦♦
You can click on the minimize button of
each form to minimize them into icons at the
bottom of the main window as Figure 5.11 shows.
To open any of the minimized windows, double
click on its icon or click on it once and then select
Restore.
♦♦
You can use the mouse to resize windows,
or to drag a window or an icon anywhere in the
RODSTAR main window.
RODSTAR |61
62 | Rod Pump System Design
6
Rod Pump System Design
You can use RODSTAR to quickly design any rod
pumping system, compare pumping units, sucker
rod designs, insert versus tubing pumps, clockwise
versus counterclockwise crank rotation, include
IPR modeling in your predictions, etc. RODSTAR can calculate the pumping speed, pump
plunger size, and rod string design for you. Also,
it can recommend motor size and pumping unit
size based on your target production. These power-
accurate and reliable.
Because RODSTAR can predict energy consumption very accurately, you can use it to select the
most economic system designs. The following
sections explain how to apply RODSTAR to solve
common design problems. As you become more
familiar with RODSTAR you will discover many
different applications for this powerful rod pump
system design tool. RODSTAR’s capability to read
Figure 6.1 - RODSTAR Summary Report
ful features help you design rod pumping systems
faster than ever before. Also, because RODSTAR
uses state-of-the-art design algorithms, it is very
RODDIAG and XDIAG files and overlay the
measured dynamometer card on the same plot as
the predicted one is very useful. With this capability you can:
RODSTAR |63
1. “History match” existing rod pumping systems
before you make a design change. This allows
you to figure out unknown quantities such as
rod-tubing friction.
2. Detect an out-of-calibration load cell (used
to record the actual dynamometer card) by
checking for a consistent shift in actual versus
predicted dynamometer card shape.
3. Detect incorrect fluid level measurements due
to foam in gassy wells.
6.1 Understanding RODSTAR’s
Output
To maximize the benefit of using RODSTAR,
it is important to understand its output. After
RODSTAR runs, it displays the summary output
report page. Also, it shows buttons on the bottom
of the output window that allows you to access the
predicted dynamometer plot, torque plot, IRP plot
(if IPR data was entered), or return to the output
report as Figure 6.1 shows.
6.1.1 Dynamometer and Permissible Load Plots
When you click on the “Dynamometer” button
then you see the predicted surface and downhole
dynamometer card plots along with the permissible load diagram as shown in Figure 6.2 . These
plots show the predicted surface and downhole
dynamometer cards, measured surface dynamometer card from a RODDIAG or XDIAG file (if
you selected that option), and the permissible load
diagram. RODSTAR uses a permissible load
diagram that shows if the gearbox or structure
of the pumping unit are overloaded or if the
minimum polished rod load is negative. This
Figure 6.2 - Dynamometer plots and Permissible Load diagram
is different than the traditional permissible load
diagram that only shows whether the gearbox is
overloaded. This extended permissible load diagram can be made up of curved lines only, combination of curved and straight lines, or straight lines
only. If the upstroke part of the predicted surface
dynamometer card exceeds the curved line of the
permissible load diagram this indicates that the
gearbox is overloaded at that point. If the dynamometer card cuts into the straight line section of
the permissible load diagram on the upstroke, this
indicates that the structure of the pumping unit is
overloaded because the polished rod load is larger
than the structure rating of the unit.
For the exact numbers of peak net gearbox torque
and gearbox loading, look at the torque analysis section of the printout. The permissible load
diagram corresponds to existing conditions if you
entered a counterbalance moment. If you did not
enter an existing max. CB moment then the program shows a permissible load diagram for bal-
anced condition (for minimizing gearbox torque).
Note!: The above discussion about RODSTAR’s permissible load diagram refers to
beam pumping units. The permissible load diagram for long stroke units such as the Rotaflex
will have straight line segments that correspond to gearbox loading or structure loading.
Please look at the structure loading number
on the first page of the output and the percent
gearbox loading under torque analysis for the
exact percent unit loading.
In addition to showing whether the gearbox is
overloaded, the permissible load diagram also
shows how well the pumping unit matches the
load requirements of your system. If the predicted
polished rod dynamometer card fits nicely in the
permissible load envelope, this indicates a good
agreement between the pumping unit and the rest
of the system.
However, if the predicted surface dynamometer
Figure 6.3 - Torque plot
RODSTAR |65
card shows a trend that is opposite that of the
permissible load diagram, this shows that design
changes are necessary to avoid overloading the
pumping unit and to better match it to the rest of
the system. If the permissible load has a trend that
is opposite than the predicted dynamometer card,
it may indicate that the pumping unit you selected
is not the best geometry for this application. Or,
that you may have to change the spm, plunger size,
rod string design, or stroke length to get a better
match between the dynamometer card and permissible load diagram.
Including prime mover speed variation and inertia
effects will alter the shape of the permissible load
diagram. The lines will be smoother if you do not
include prime mover speed variation. If you include speed variation the permissible load diagram
will tend to reflect changes in polished rod load.
This is because the permissible load diagram in
RODSTAR includes the effect of rotating and articulating moments of inertia. As the prime mover
speed changes, this causes changes in polished rod
velocity and acceleration which in turn changes the
polished rod load and the distance between the dynamometer card and the permissible load diagram.
The output window has new buttons that allow
you to animate the calculated dynamometer cards.
Figure 6.2 shows a “play” button (the one with the
double arrow) which causes small dots to move
around the surface and downhole dynamometer
Figure 6.4 - Inflow performance relationship (IPR) plot
cards; a “stop” button which makes the movement
stop; and a “step” button (the one with the single
arrow) which lets you move the dots one time-step
at a time, while holding the button down moves
the dots in slow motion. This facility can be used
to get a better understanding of rod stretch effects
and other phenomena such as the position and
speed of the pump plunger and how this relates to
the surface dynamometer card.
From this screen you can look at any other part of
the output by clicking the appropriate option at
the bottom of the screen. For example, to view the
torque plots click on Torque. Also, you can select
to view the report on screen, or you can send the
output to the printer. After you are done viewing
the output, close the screen by clicking on Close.
6.1.2 Torque Plot
When you click on the “Torque Plot” button
RODSTAR displays the net gearbox torque plots
for existing and balanced conditions. If you entered
an existing maximum counterbalance moment,
then you may see a plot with up to three curves:
one for existing conditions, one for balanced conditions for minimum torque, and one for minimum
energy consumption. If there is no difference between the curve for minimum torque and the one
for minimum energy, then the program shows only
two curves (existing and balanced). If you selected
“unknown” max. CB moment then RODSTAR
will only show one curve if there is little difference
between balanced for min. torque vs balanced for
minimum energy consumption (see Figure 6.3).
Otherwise, it will show two balanced curves: one
for minimizing torque and one for minimizing
energy consumption.
6.1.3 IPR Plot
When you click on the “IPR Plot” button, RODSTAR displays separate oil, water, and fluid production versus flowing bottomhole pressure plots
as Figure 6.4 shows. Also, it shows a line with the
current bottom hole pressure and the test points
you entered. The line below the title of the plot
shows the correlation you selected to use for the
oil IPR and if you selected the Fetkovich method,
it shows the value of n. If you only enter one test
point, n is set to one. If you enter two or more test
points then RODSTAR calculates the value of n
by doing a log-log plot. For water, RODSTAR
uses a straight line IPR.
6.1.4 Report
To see the report, click on the “Report” button.
You can scroll this window using the mouse by
clicking or the up or down arrows at the top or
bottom of the range bar on the right edge of the
window.
Or, you can click and drag the range bar or the
report itself with the mouse.
Input and Output Summary
The summary report that appears when you first
run RODSTAR shows input data on the left side
of the page and calculated numbers on the right
size. The top part of the printout shows the company name, well name, user name, date of the run,
and comment. Following is a detailed explanation
of each item on the output.
Polished Rod Loads and Horsepower
The peak and minimum polished rod loads show
the polished rod load fluctuation predicted by
RODSTAR. The polished rod horsepower shows
how much work the pumping system is putting
into the rod string to lift the predicted production
from the present fluid level to the surface.
If you entered a target production or used IPR data
to determine the target production, RODSTAR
calculates the SPM required to get the target production.
System Efficiency
The system efficiency is calculated by regarding
the whole pumping system as a black box with
electricity going in and produced fluid coming out.
This number shows how efficiently the system converts electric power to work needed to lift the produced fluid to the surface. A system efficiency of
45% or above is excellent. In General, deeper wells
will have lower efficiencies than shallow wells since
deep wells have more rod-tubing frictional loses.
Efficiencies of 35%-45% are average, while system
efficiencies of less than 35% are poor and can usually be increased by using a longer, slower stroke
(with larger pump plunger).
Permissible Load HP
Permissible load horsepower is defined as the area
bounded by the upper permissible load line, limited by the structural rating of the pumping unit
and the lower permissible load line, limited by zero
minimum load.
The ratio PLHP/PRHP (permissible load HP
divided by polished rod HP) is a number that
should be as large as possible without overloading
the pumping unit. The larger this number is, the
more of the pumping unit potential capacity you
are using.
Fluid load on Pump
Fluid load on the pump shows how much fluid
load the plunger is carrying on the upstroke. This
is a function of pump depth, fluid level from surface, and plunger size. Fluid load on the pump is a
function of pressure difference across the plunger
and pump plunger diameter.
Unit Structural Loading
Pumping unit Structural Loading indicates whether or not the pumping unit structure is overloaded.
This is a function of the peak polished rod load
RODSTAR |67
and the structural capacity of the pumping unit
(the middle number in the API pumping unit
designation).
Buoyant Rod Weight
Buoyant rod weight shows how much the rod
string weighs in fluid. Since the rod string is immersed in the fluid inside the tubing, it weighs
less than in air. You can compare this number to
a measured standing valve load. A good standing
valve check should be close to the weight of rods
in fluid as calculated by RODSTAR for a pump
that is in good mechanical condition. If these two
numbers differ by more than 10% and the standing
valve is in good condition, it may be an indication that the load cell is out of calibration or that
the standing valve load was incorrectly measured.
Also, the sum of the buoyant rod weight plus fluid
load on the pump should be close to the traveling
valve load for a good pump.
N/No’ and Fo/Skr
The dimensionless numbers N/No’ and Fo/SKr
are defined in API RP 11L1 . N/No’ is the ratio
of pumping speed to natural frequency of the rod
string. Fo/SKr is the rod stretch caused by the
static application of fluid load, as a percent of the
polished rod load stroke. In general, the higher
the Fo/Skr is, the shorter the pump stroke will be.
Also, the higher the N/No’ the larger the pump
stroke is. These numbers also relate to system efficiency. In general, the larger N/No’ is, the lower
the efficiency will be. The larger the Fo/SKr is,
the better the system efficiency is. However, this
relationship is not linear.
For low Fo/Skr numbers (below 0.25) fiberglasssteel rod strings will have very low system efficiencies and should be avoided. For fiberglass rods try
to keep Fo/Skr above 0.3 and below .8 for best
1
API RP 11L (Third Edition) Recommended
Practice for Design Calculations for Sucker Rod
Pumping Units. American Petroleum Institute,
Dallas TX.
results. Also for fiberglass rod strings, you should
keep N/No’ below 1.0 and above .4 for best results.
Prime Mover Speed Variation
If you select to have RODSTAR calculate the motor speed variation for you then this section shows
what this number is. For NEMA D motors this
number will vary from 2% to 14% depending on
motor size. For correctly sized ultra high slip motors it can be as high as 50%. If motor speed variation is not considered then this will be indicated
on the output report.
Pumping Unit Data
This section (see Figure 6.5) shows the pumping
unit you selected, the pumping unit ID, the calcu-
lated stroke length, the structural unbalance, the
crank offset angle, crank rotation with the well
to the right, and the crank hole number. If you
entered your own pumping unit dimensions for a
unit not in the program’s database, if the calculated
stroke length is different from what you think it
should be, check the pumping unit data to make
sure you entered the right dimensions. If you selected to include speed variation and inertia effects
in the calculations, RODSTAR will also print the
rotating and articulating moments of inertia.
Torque Analysis and Electricity Consumption
In this section, the program prints the predicted
peak gearbox torque, percent gearbox loading,
cyclic load factor, maximum counterbalance moment, and counterbalance effect. Also, it calculates
electricity consumption. RODSTAR predicts the
KWH consumed per day, the estimated monthly
Figure 6.5 - Section of RODSTAR Output Report
RODSTAR |69
bill, and cost per barrel of fluid and per barrel of
oil per day. Use the cost per barrel numbers when
comparing system performance to ensure a valid
comparison. This is because a system that shows
a lower monthly bill may also be producing less
fluid.
If you enter a non-zero maximum counterbalance
moment the program calculates the above numbers for both existing and balanced conditions. If
the existing max. CB is unknown, it will calculate
the above numbers for balanced conditions only.
RODSTAR has the capability to balance pumping
units for minimum torque and minimum energy. If
the maximum counterbalance moment for minimum energy equals the one for minimum torque
then the program shows only one recommendation
for balanced conditions. However, if the two values
are more than 2% different then it shows two balanced columns: One for minimum torque, and one
for minimum energy. The torque plots show how
net gearbox torque changes throughout the pumping cycle for existing and balanced conditions.
To maximize gearbox life you must keep gearbox
loading less than 100%. The cyclic load factor
indicates how smooth the gearbox torque is. The
smaller this number is, the more uniform the net
gearbox torque is. Also, a smaller cyclic load factor
will result in higher system efficiency because of
less thermal losses in the motor.
Tubing, and Pump Information
Here you see the tubing inside and outside diameters, the anchor depth, the calculated tubing
stretch, the upstroke and downstroke rod-tubing
friction factors you entered or that were calculated
by RODSTAR, pump load adjustment., etc. Also,
this section shows the pump depth, the pump
type, and plunger size.
RODSTAR uses the pump volumetric efficiency
you enter to calculate the expected production rate.
When you ask the program to calculate the spm
by entering a target production, it will calculate a
larger spm if you enter 80% pump efficiency than
when you enter 90% pump efficiency.
Tubing, Pump and Plunger Calculations
This section shows tubing stretch and production
loss due to tubing stretch, gross pump stroke, the
Figure 6.6 - System cost analysis
Figure 6.7 - IPR report
pump spacing recommendation, minimum required pump length, and recommended plunger
length. The pump spacing recommendation should
be used as follows:
After working on the well and before you
are ready to restart the pumping unit, make
sure the tubing is full of fluid. Then lower the
rod string slowly until it tags bottom. Then
raise the rod string a distance equal to the one
recommended by RODSTAR next to: “Pump
spacing (in. from bottom): ” Then, attach the
polished rod to the bridle with the unit stopped
at the very bottom of the downstroke.
Please note that the working fluid level makes a
big difference in pump spacing and pump length.
This is especially true for fiberglass rods since the
plunger travel is strongly dependent on fluid load
on the plunger.
Rod String Design and Stress Analysis
This section shows the rod string design and service factor you selected, the calculated percent rod
loading for each rod section, the maximum and
minimum stresses at the top, and the bottom minimum stress for each rod section. To ensure your
rods are in tension, do not include buoyancy effects
(this should always be the case for steel rods).
Then, make sure there are no negative stresses on
any other rod section other than the sinker bar section on the bottom of the rod string.
If you are using fiberglass rods you would not want
to use a design with a negative bottom minimum
stress on the fiberglass section even with buoyancy
effects included. Compressive loading will cause
fiberglass rods to part. Also, to maximize rod
life, stress loading must be less than 100% in all
cases. For sinker bars, RODSTAR calculates stress
loading, top maximum and top minimum stresses
based on the elevator neck or pin undercut diameter of the sinker bars. However, RODSTAR still
uses the full body diameter in the calculation of
stress at the bottom of the sinker bar section.
Rod String and Pumping Unit Cost Analysis
This section shows the cost of each rod section as
well as the total rod string cost (see Figure 6.6).
Also, below the rod string cost is the pumping
unit cost. RODSTAR shows the cost information
only if you select this option in Setup. You must
first enter rod string and pumping unit cost data in
Setup before RODSTAR can show you accurate
cost information here.
Inflow Performance Relationship Information
This section shows the correlation used for oil
IPR, mid-perf depth, the static bottomhole pressure, and the bubble point pressure (if entered) or
whether the well is producing below the bubble
point pressure. Also, it shows a table of input test
point data of flowing bottomhole pressure versus
measured production, and a table of pressure vs.
production table. As Figure 6.7 shows, this table
RODSTAR |71
shows separate oil, water, and fluid production
rates for different pump intake pressures.
6.2 RODSTAR (Deviated Mode)
Output
In addition to the output quantities discussed
above, the deviated mode calculates and prints
numbers and plots that are related to wellbore
deviation. Following is an explanation of these
outputs that are unique to the deviated mode.
6.2.1 Deviation Plots
the bottom. It will display the first deviation
related plot as shown in Figure 6.9. This plot
shows side load as a function of measured depth.
All deviation plots show colored lines that
correspond to different sections of the rod string.
The calculated side load affects is used by the
program to determine the number of rod guides
and their spacing, using rod guide manufacturer
recommendations. Click on the “Next” button
on the bottom of this plot to see the rest of the
deviation-related plots.
The next plot is the maximum and minimum axial
loading. This plot shows how the maximum and
minimum rod loads change as a function of measured depth.
The buckling tendency shows the buckling ten-
Figure 6.8 - RODSTAR (Deviated Mode) First Displayed Page
After RODSTAR runs, it will display the
summary output page as shown in Figure 6.8.
When you click on the “Dev. Plot” button on
dency load as a function of measured depth. It is
generally accepted that buoyancy does not cause
buckling. The bottom of the rod string is sub-
Figure 6.9 - Side Load Plot
jected to negative loads because of pump friction
and other frictional effects due to wellbore deviation. According to a paper titled “Interpretation of
Calculated Forces on Sucker Rods” by J.F. Lea and
P.D. Pattillo, published in SPE production and Facilities, February 1995, the critical load necessary
to buckle a rod string is calculated as follows:
Where:
w = rod weight in fluid
I = moment of inertia of cross section (in4)
E= elastic modulus of rod = 30.5x10⁵ psi for steel
The Moment of inertia of the rod section (“I”
above) can be calculated as follows:
In the same paper referenced above, the author
shows a table of critical forces and length that will
cause rods to buckle. According to this table, a 3/4”
rod would buckle if it subjected to a negative load
of only 37.2 lbs and if at least 26.1 feet of the 3/4”
section is in compression. For 7/8” rods, buckling
would occur if the negative force on the bottom
is 56.2 lbs and the negative portion is longer than
28.9 feet long. As these examples show, the only
way to be sure the rods will not buckle is to keep
them in tension.
The Dogleg severity in degrees per 100 feet, represents the rate of change in the inclination and
azimuth of the bore hole with respect to measured
depth. Dogleg severity is not used to calculate side
load. The Dogleg severity plot is a useful guide
that shows how sharply the curvature of the wellbore changes. The same dogleg severity close to the
RODSTAR |73
Figure 6.10 - Deviation plot page
74 | Well Information
surface of the well will result in a larger side load
as compared to the same dogleg severity close to
the bottom of the hole. This is because the tension
in the rods is much higher at the surface and thus,
it results in larger side loads as compared to the
bottom of the rod string where axial load is much
lower and therefore the rods can go around the
bent more easily.
The rest of the deviation plots show different views
of the wellbore.
If you click on the “Report” button shown in
Figure 6.8, the program will show you a one-page
summary of all the deviation plots as shown in
Figure 6.10. This page looks exactly the same as
the printed page when you print the report. You
can also page up or down using the up or down arrow keys at the top of the report page to see all of
the report pages, including the rod guide spacing
recommendation pages.
Figure 6.11 - 3D rod guide recommendation plot
6.2.2 Rod Guide Recommendation Output
RODSTAR shows rod guide spacing recommendations depending on the calculated side load and
the type of rod guides you selected in Setup as
shown in Figure 6.10. These are the last pages of
the output report. RODSTAR also shows you the
recommended placement of the rod guides using
a 3D plot of the deviation survey. If you manually
enter the number of guides per rod, this 3D plot
will show your entered data. If RODSTAR calculates the rod guide placement for you, then the
program’s recommendation is plotted on the 3D
graph.
6.3 Rod Pump System Design
Guidelines
When designing a rod pumping system you
must specify the equipment, strokes per minute,
and stroke length required to get the desired
production at the lowest possible cost. In your
efforts to select the best system design for your
well you will be mostly concerned with the
following parameters:
♦♦ Production Rate
♦♦ Capital costs
♦♦ Rod loading
♦♦ Gearbox loading
♦♦ System efficiency and power costs
Ideally, the system you select will give the highest
present value profit after tax, considering capital
and operating costs. Up to now, rod system design
was a tedious trial and error process that usually resulted in a system that could be far from
ideal. Since achieving an optimum design requires
equipment and data that may not be available, only
the most obvious system parameters are usually
considered. In most cases production rate is of
highest priority, followed by rod loading, gearbox loading, and energy cost. If electricity cost is
high, you can lower it by using a larger pump and
RODSTAR |75
a slower pumping speed. However, a large pump
will increase rod loading and gearbox torque.
Also, a large pumping unit must be used. This will
increase capital cost. On the other hand, a small
pump demands a faster pumping speed and longer
stroke to maintain production. This increases energy consumption but reduces the required pumping
unit size. Usually, you must reach a compromise
between efficiency, rod loading, pumping unit size,
and cost.
A very important aspect of system design is pumping rate. If you know the maximum production
rate you can expect then design the pumping system for a production rate a little higher than that.
This ensures enough pump capacity to account for
normal pump wear and inaccurate data. However,
if the pumping rate is substantially higher than
what the well is capable of producing, then the
well will pump off. Fluid pound is a problem that
results from the common practice of over-designing the pumping capacity. Fluid pound is damaging to pump, rods and pumping unit. If you do not
take steps to minimize fluid pound it will reduce
efficiency and equipment life. You can reduce fluid
pound by slowing down the unit, shortening the
stroke length, using a smaller pump, or by installing a percentage timer or pump off controller.
Because RODSTAR can simulate fluid pound,
you can use it to see what will happen if the well
pumps off.
6.3.1 Shallow, High Rate Well Simulation
RODSTAR can simulate any pumping unit geometry and gives accurate results for any pump depth
or production rate. This is especially significant
for shallow well applications because conventional
design computer programs such as the API RP
11L and other wave equation programs give poor
results. This is because at shallow depths, polished
rod load is increasingly dependent on the dynamic
effects of fluid in the tubing. This is especially
true for high production rate shallow wells (pump
depth less than 4000 feet with larger than 2.00”
plunger).
To accurately simulate these wells, RODSTAR uses
two wave equation models simultaneously, one for the
rod string and one for the fluid in the tubing. This
unique capability allows very accurate predictions.
RODSTAR can predict the expected surface and
downhole dynamometer card shapes common to
shallow, high rate wells. When designing shallow high rate wells it is recommended that you
use pump efficiencies of 90%-95% to avoid underpredicting peak polished rod load, torque, etc.
This higher pump efficiency will result in higher
fluid velocity in the tubing and higher fluid inertia forces on the plunger. However, when you are
trying to “history match” an existing system, you
may need to use a pump efficiency of less than 90%
to better match the actual pump slippage of your
system.
6.3.2 Selecting the Target Production
To avoid severely over-sizing the displacement
capacity of your pumping system, design it with a
pump efficiency of 80%-85% or even 75% if you
expect the downhole pump to wear out quickly.
This ensures that you will get your production
without grossly over-designing the system.
To minimize energy consumption and stress loading, use the largest plunger diameter and slowest pumping speed combination possible without
overloading the rod string and pumping unit. If
you have to make a choice between stress loading
and power consumption, opt for lower stress loading especially if you are close to 100% since rod
breaks are more costly than a slightly lower system
efficiency.
Note that these are only general guidelines. Economics and local field conditions may require a
different design philosophy than the one described
above. Regardless of your objectives and design
philosophy, with RODSTAR you can design rod
pumping systems faster and more accurately than
with any other computer program.
6.3.3 Avoiding Rod Compression
RODSTAR calculates rod stresses at the top and
bottom of each rod section. It calculates the maximum and minimum stress at the top of each rod
section in order to calculate the percent stress loading. It also calculates the minimum stress at the
bottom of each rod section. The bottom minimum
stress shows if the rods are in compression.
Steel rods can tolerate some compressive force but
fiberglass rods cannot tolerate any compression
at all. This is why fiberglass rods must have steel
rods or sinker bars at the bottom. The weight of
the sinker bars overcomes the opposing hydrostatic
force and pump friction. If correctly designed, the
sinker bars or steel rods ensure that the fiberglass
rods are always in tension.
Although steel rods can be subjected to some compression without adverse effects, excessive negative
stresses can cause buckling problems. The recommended way to use RODSTAR to determine if
your rods may be subjected to compression is to
run the program without including buoyancy
effects. Then, add sinker bars or sinker rods to
overcome the negative stresses at the bottom
section of the rod string (above the sinker bar
section) . Other ways of minimizing buckling
problems include using smaller pumping speeds
and avoiding use of small diameter rods such as
5/8” or even ¾”.
6.3.4 Minimizing Power Consumption
In general, the slower the pumping speed and the
larger the pump plunger size, the less energy the
pumping system will use. However, minimizing
energy consumption must not be the sole purpose
of system design because a large pump plunger
diameter will result in large polished rod load and
gearbox torque. This will require the purchase of a
larger unit, larger rods and bigger prime mover. To
come up with the best pumping system design you
must consider the economics of the whole system
and whether you plan to use existing equipment or
buy new ones.
RODSTAR’s power and ease of use allows you to
get the most economic pumping system based on
your economic criteria. Because RODSTAR calculates the predicted energy consumption, rod sizes,
rod loading, and recommends a pumping unit size,
it provides you with the data you need for sound
economic decisions.
6.3.5 Reducing Gearbox Torque
Sometimes, using the largest unit stroke may not
be the best way to maximize production since it
can result in severe gearbox overload. If this occurs you may be able to use the next smaller unit
stroke and speed up the unit to get your production without overloading the gearbox. Another way
of reducing gearbox loading is by using a smaller
pump plunger. Another way is to use a lighter rod
string by using either high strength steel or fiberglass rods.
Also, you can reduce gearbox torque with an ultra
high slip motor. RODSTAR can predict the gearbox torque depending on the pumping unit size
and ultra high slip motor size. Also, RODSTAR
can calculate the motor speed variation and power
consumption very accurately.
6.3.6 Using RODSTAR for Correct Equipment Sizing
When designing a new rod pump system you must
ensure that the system you select has sufficient capacity to produce the well under the heaviest loads
possible during its operating life. For most systems
this will occur when the fluid level is at the pump.
Therefore, even if you do not expect the fluid level
to be at the pump, it is a good idea to design the
pumping system (especially when using steel rods)
for fluid level at the pump. This ensures that the
equipment you plan to use will not be overloaded if
the fluid level drops in the future.
For systems with fiberglass-steel rod strings, you
may get higher gearbox torque loads and higher
polished rod horsepower when the fluid level is
above the pump. This occurs because fiberglass rods
RODSTAR |77
are very sensitive to fluid load. When the fluid
level is above the pump, the fluid load on the pump
is reduced. This causes a longer pump stroke which
in turn affects the shape of the surface dynamometer card making it fatter. This in many cases brings
the predicted surface dynamometer card closer to
the permissible load diagram causing the gearbox
load to increase. Also, when the area of the surface
dynamometer card increases, the system requires
a larger motor size. This means that when you use
fiberglass rods you should run system simulations
using different fluid levels (within the expected
fluid level range) to see which fluid level results in
the highest loads and largest required motor size.
Using different fluid levels also affects the calculated pump stroke length and therefore the required
pump length and pump spacing . RODSTAR can
recommend a NEMA D motor size based on the
fluid level or pump intake pressure you enter.
TIP: You can speed up your system design considerably by asking RODSTAR to design a rod string
for you. Even if you do not plan to use the design
RODSTAR recommends, it is easy to “grab”
RODSTAR’s recommended design and modify
it. To do this, after the program runs, go to the
rod string entry screen and select the “Manual rod
string entry” option. The program will default to
the rod string it calculated, and it will display this
data as if you had entered it yourself. So, you can
simply change only the data you want to modify.
Please keep in mind that RODSTAR expects the
length of the rod string you enter to be within 50
feet of the pump depth. However, it cannot be
longer than the pump depth.
6.3.7 Using RODSTAR for Diagnostic Analysis
Although RODSTAR is primarily a design tool it
can be a very powerful diagnostic aid, when used
in conjunction with RODDIAG or XDIAG. This
is due to the powerful overlay feature that allows
direct comparison of predicted versus measured
dynamometer cards.
Using RODSTAR’s Dynamometer Overlay Feature
This feature has many different uses. For example,
it can help you figure out if your load cell is out
of calibration, if the fluid level you measured was
incorrect, etc. RODSTAR can help you find these
problems by comparing the shape and load range
of the measured dynamometer card versus the one
predicted by the program. Also, it can help verify
downhole problems such as a worn pump, leaking
traveling or standing valves, deep rod parts, stuck
pump etc. You can simulate a worn out pump or a
deep rod part by entering a fluid level of zero feet
from surface. This will result in zero fluid load on
the pump plunger.
RODSTAR cannot simulate a traveling valve leak,
a hole in the pump barrel, or a sticking pump.
But, it can predict what the dynamometer card
should look like if there were no problems. Then,
by comparing the actual dynamometer card shape
with the theoretical shape, you can have more
confidence in your diagnosis of the problem. For
example, if you have a traveling or standing valve
leak or a worn out pump, then the pump will be
doing less work and the surface dynamometer card
will have less area than the theoretical polished rod
dynamometer card.
If the pump is sticking, or if there is more friction
than normal between rods and tubing (due to paraffin, scale, etc.), the measured dynamometer card
will be fatter than normal. The theoretical polished
rod dynamometer card predicted by RODSTAR
(for average friction calculated by the program)
will be smaller than the measured dynamometer
card. By entering a larger rod-tubing friction coefficient you can get a better match between actual
and predicted dynamometer cards. This technique
helps you figure out what rod-tubing friction factor
to use for better simulation of your rod pumping
wells.
Rod-tubing friction is especially important
for fiberglass rods. Higher friction than
normal may actually reduce the area of the
predicted surface dynamometer card because
it causes the rods to stretch which results in a
small stroke at the pump.
RODSTAR allows you to change the rod-tubing
damping coefficients for upstroke and downstroke
and also the friction coefficient between rods and
tubing for each section in the rod string. This
allows you to better simulate use of different rod
guides, or more exactly match the correct friction
between rods and tubing for a better match with
the measured dynamometer card.
6.3.8 Using RODSTAR for better Wellbore Designs
RODSTAR can be a very useful tool in helping
you optimize the wellbore trajectory of your
deviated wells to minimize side loads, rod-tubing
wear and buckling, and to reduce lifting costs by
improving system efficiency.
The optimum wellbore path will be different for
each well, but by using RODSTAR you can determine which is the best wellbore trajectory by trial
and error. Normally, wellbores that avoid sharp
turns and abrupt builds to the deviated section will
produce better results.
With careful planning and wellbore path control,
deviated well design can be improved with RODSTAR.
Theta Oilfield Services, Inc., 3075 E. Imperial Hwy Suite 125, Brea, CA 92821 USA
Phone: (562) 694-3297 | gotheta.com

rodstar - doverals.com

Transcription

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