Snubbing nugget

Hydraulic Workover Unit
• A ‘Snubbing System’ is basically a well
servicing system capable of running and
retrieving jointed pipe under live well
conditions (but not necessarily high pressure).
• A snubbing unit or Hydraulic Workover (HWO)
unit can be used for:
– drilling new wells (underbalanced if
required)
– side-tracking existing wells (underbalanced
if required)
– completion (underbalanced if required)
– fishing (underbalanced if required)
– gravel packing (underbalanced)
– perforating (underbalanced)
– clean-out (underbalanced)
• Advantage is that the well does not require
killing.
• Can carry out some work as a rig as long as
tubulars are less than 103/4” OD.
• HWO Unit useful for pulling CT completions
Live Well Workovers
• less fluids lost to formation = less damage
• shorter time with well off-line
• less problems with kill fluids
Hydraulic Workover Unit
• HWO Definitions
‘Snubbing’
= process of tripping pipe in well
which as a surface pressure
great enough to eject the pipe
from the well if no restraining
force is applied.
‘Stripping’
= relates to the same operation,
but where the surface pressure
and workstring combination
would result in the workstring
failing into the well under its
own weight if unrestrained.
‘Lubrication’ = process of inserting and
removing BHA and toolstrings
from the well.
‘Hydraulic Workover’
(HWO)
= Unit to run/pull tubulars in/out
of well (with or without
surface pressure), using
hydraulic power to transmit
the required forces to the pipe.
Snubbing - An Introduction
• Snubbing is a live well workover process
that uses standard jointed tubulars
• Rig (cable) assisted snubbers date from the
1930’s
• Hydraulic snubbers a later addition.
Components
• A pipe movement system - cable assisted or
rig assisted
• A sealing stack of pipe rams that allows
passage of tool joints and equipment into
and out of a well under pressure.
A view of the pressure connection
tube between the upper isolation
chamber and the well.
Hydraulic snubber - top
of stroke.
Schematics
from Cudd
Pressure
Control
Pipe slip
elements in
hydraulic
snubber
1. Close upper or
traveling slips.
2 Open lower or
stationary slips.
3. Activate hydraulic
pressure to pull down
on pipe and force it
into the well.
Weight Necessary to Pull
Wireline into the Well, lbs
Weight Necessary to Pull Wire into a Wellhead
Under Pressure
500
450
400
350
300
250
200
150
100
50
0
0.072" Wire
0.092" Wire
0.108" Wire
0.125" Wire
3/16" Wire
5/16" Wire
0
2000
4000
6000
8000
Well Head Pressure, psi
10000
Snubbing Force or Weight
Required to Enter Wellhead,
lbs
Snubbing Pressure vs. WHP and Wire or
Tubing Size
50000
45000
40000
35000
30000
0.108" Wire
3/16" Wire
1.5" CT
2-3/8" Tbg
2-7/8" Tbg
3-1/2" Tbg
4-1/2" Tbg
25000
20000
15000
10000
5000
0
0
1000
2000
3000
4000
Well Head Pressure, psi
5000
Hydraulic snubber
nearing bottom of
stroke.
1. Close lower or
stationary slips.
2. Open upper or
traveling slips.
3. Activate hydraulics
to extend cylinders.
Tool joint nearing
slips.
Stop tool joint
immediately above top
pipe ram on snubbing
stack.
Pipe seal
elements
Tool joint above top
ram. System
pressurized below.
Middle pipe seal closed
Ready to bleed
off upper
straddled area.
Upper straddled area
bled off.
Open upper ram and
pass tool joint into
upper straddled area.
Close upper ram and
prepare to pressurize
upper straddled area.
Upper straddled area
pressurized, prepare to
open middle ram.
Open middle ram
and pass tool joint
into well.
Traveling
slips
Braided line
and pulleys
on the rig
floor.
Stationary
slips
Rig assisted
snubbing using
rig draw works
and snubbing
stack below the
table.
Perforating Guns Run Under Pressure
Description of job
Length of
guns
Location
Depth
of well
Surface
PSI
1,200’
Valhall/ N. Sea
13,123
2900
TCP guns 33/8” w/auger system using DHSV
250’
Valhall/ N. Sea
12,467
2755
TCP guns 41/2” w/ aligning knobs using DHSV
500’
Valhall/ N. Sea
14,108
3190
Halliburton Deployment system TCP guns 41/2”
850’
Statfjord B
13,123
1957
Halliburton Deployment system TCP guns 41/2”
1,100’
Statfjord C
14,108
1812
TCP guns 41/2” using DHSV
450’
Gulfaks B
15,420
1595
TCP guns 41/2” using DHSV
600’
Gulfaks C
15,092
1740
Halliburton Deployment System TCP guns 4 ½”
2,800’
Statfjord B
16,076
3552
TCP guns 4 ½” using DHSV
1,800’
Sleipner
13,780
3045
TCP guns 4 ½” using DHSV
3,200’
Gulfaks B
17,717
2755
TCP guns 4 ½” Using FIV Valve
1,400’
Veslifrik
12,795
2610
Halliburton Deployment System TCP guns 4 ½”
950’
Gulfaks C
13,780
3190
Halliburton Deployment System TCP guns 4 ½”
1,100’
Gulfaks A
13,451
2682
TCP guns 33/8” using DHSV