Laboratory Comparisons of CO2 and Rich Gas Injection on Oil

Transcription

Laboratory Comparisons of CO2 and
Rich Gas Injection on Oil Recovery from
Bakken Reservoir Rock and Shales
2014 Williston Basin Petroleum Conference
Bismarck, North Dakota
May 20–22, 2014
*Steven B. Hawthorne, Ph.D., Charles D. Gorecki, James A.
Sorensen, SPE, Edward N. Steadman, and John A. Harju
Energy & Environmental Research Center
Steve Melzer
Melzer Consulting
© 2014 University of North Dakota Energy & Environmental Research Center.
Greg Hild (Chevron), November 5, 2013, SPE
Unconventional Resources Conference.
“We must start thinking way outside of the box.”
Non-traditional thoughts on
CO2 and associated gas EOR from the lab.
The International Center for Applied Energy Technology®
Executive Summary
Background:
Present methods leave ca. 95% of Bakken oil in
the reservoir.
Good news:
In the lab, we can recover more than 90% of oil
from upper, lower, and middle Bakken rock using
only CO2 (and maybe using associated gas).
Bad News:
We need to understand the controlling
mechanisms better to make it cost-effective.
(Even a 1% increase in recovery could be ca. 2-9 billion
barrels.)
Potential for Associated Gas EOR Assumptions
Application of the U.S. DOE methodology for estimating CO2 EOR and storage
capacity in the Bakken suggests 37 to 58 Tcf of CO2 would yield 4 to 7 billion
bbl of incremental oil.
This assumed a utilization factor of approximately 8 Mcf of CO2 per barrel of
incremental oil.
North Dakota Bakken wells produce approximately 1 Bcf/day of associated gas.
Preliminary data suggests that the ability of methane (and 85/15 methane/ethane)
to remove oil from Bakken rocks may be similar to that of CO2.
• When corrected for density differences, on a molar basis it appears that 1asdlkjf
1 Bcf/day of Bakken gas could be as effective for EOR as 1 Bcf/day CO2.
• For Bakken associated gas, let’s assume a potential range of utilization
factors of 3 to 16 Mcf per barrel of incremental oil.
Potential for Associated Gas EOR
Using previous assumptions yields a potential for Associated Gas EOR:
• 1 Bcf/day of Bakken associated gas could yield between 66,000 and
330,000 bbl of incremental Bakken oil/day.
• For perspective, the Weyburn/Midale EOR projects use about 200
MMcf/day CO2, so 1 Bcf/day of Bakken associated gas could
possibly supply 5 Weyburn/Midale-scale EOR operations.
What are we trying to do, and why?
Hypothesis:
EOR mechanisms will be very different in the Bakken than
in conventional reservoirs. This may mean that different
fluids and different conditions (vs MMP) may be effective
(or not).
Approach:
If we can understand and exploit the controlling EOR
processes, we can recover more oil.
So—how do we do this?
Differentiate, understand, and exploit the physiochemical
processes that control conventional and unconventional
reservoir oil recovery.
Most of the concepts have been
developed using CO2, but have recently
been applied to “associated gas.”
 MMP (minimum miscibility pressure)
 Rock extractions at reservoir conditions.
How do MMP values with CO2 and
associated gas compare under Bakken
conditions (110 C)?
MMP by vanishing
interfacial
tension/capillary
rise.
1.12, 0.84, 0.68 mm i.d.
Patent pending
MMP by capillary rise.
Bakken Crude Oil X, Capillary MMP
7
Capiillary Height, mm
6
RSQ =
0.998
0.997
0.991
MMP =
3738
3632
3628
y = ‐0.0022x + 8.1397
R² = 0.9982
5
MEAN
3666
SD
RSD
62
2%
y = ‐0.0015x + 5.4982
R² = 0.9967
4
3
2
y = ‐0.0011x + 3.9581
R² = 0.9912
1
0
500
1000
1500
2000
2500
3000
3500
Pressure (psi)
confidential
MMP (psi) Values for Bakken Live Oils
Live oil A
Live oil B
129 C
126 C
CO2
CO2
Cap Rise
EOS
slim tube
3180 ±114
3196 ±139
3220
3150
3161
Capillary Rise MMP CO2 and Methane Comparison (psi)
CO2
Live oil A
Well head oil B
Well head oil C
Conventional
CH4
CH4/CO2
110 C
110 C
110 C
3180 ±114
4010 ±131
3254 ±145
5330 ±181
5316 ± 58
6379 ±142
1.7
1.3
2.0
42 C
1492 ± 45
3793 ± 111
2.5
MMPs with methane are higher than with CO2,
but still within reasonable Bakken pressures.
So MMP is higher with CH4 than CO2, but
can we get oil from the rock?
Four general mechanisms for CO2 EOR
1.
CO2 “flushes” the oil through the rock (conventional reservoirs
only—mimicked by the slim tube?).
2.
CO2 changes the bulk oil to make the oil more mobile.
> swelling, lower viscosity
3.
Oil is mobilized by the CO2.
> suspension, solvation of oil hydrocarbons
4.
A “new” mobile phase of mixed CO2/oil is produced at a
threshold pressure.
> a functional definition of multiple contact miscibility
Miscible or
immiscible
mechanisms
Hypothesis: The mechanism(s) for CO2 EOR in the
Bakken will be different from conventional
reservoirs.
• Conventional reservoirs: CO2 sees the reservoir as a rock with
interconnected porosity, and flows through the pore throats of the
reservoir rock. Oil is produced by sweeping (“plug” flow), swelling,
lowered viscosity, and (with enough pressure) multiple contact “miscibility.”
Displacement is the major mechanism for recovery.
• Fractured reservoirs: CO2 no longer flows through the reservoir rock.
Instead, it flows rapidly through fractures to contact exposed surfaces of
the reservoir rock.
The rock sees that it is soaking in CO2, but not being swept internally
by CO2. “Plug” flow is no longer relevant.
Implications? CO2 must mobilize oil from the rock by
some mechanism other than sweeping it from the rock.
S3
Slide 13
S3
"Surround" is optimistic - how about contact the exposed units
Steve-HP, 10/22/2013
Four Three general mechanisms for CO2 EOR in
the Bakken play.
1. CO2 “flushes” the oil through the rock (conventional reservoir only).
Mimicked by slim tube (?)
2. CO2 changes the bulk oil to make the oil more mobile.
> swelling, lower oil viscosity
3.
Oil is mobilized by the CO2.
> suspension, solvation of oil hydrocarbons
4.
A “new” mobile phase of mixed CO2/oil is produced.
> a functional definition of multiple contact miscibility
Hypothetical Steps in CO2 EOR
for fracked reservoirs
The hypothetical steps address transporting the oil in
the rock matrix to the bulk CO2 in the fractures.
These mechanisms do NOT address subsequent
production/recovery steps.
Hypothetical Steps in CO2 EOR
for fracked reservoirs
1. CO2 flows rapidly into fractures, displacing some oil/water and
contacts exposed rock surfaces. The rock now only sees nonflowing (static) CO2.
2. CO2 starts permeating the rock, carrying oil in, which could lower oil
production during the initial exposure.
3. At the same time, oil near the rock surface swells, which could
increase initial production of incremental oil.
4. As the CO2 more deeply permeates the rock, oil production
continues to be enhanced by swelling and lower viscosity.
5. When CO2 has fully permeated the rock (no ∆ P), oil is produced
only by diffusion-based concentration gradients from the rock to bulk
CO2 phase.
CO₂
Step 1
Initial injection: CO2
flows rapidly through
fractures.
Step 2: CO2 starts to permeate rock based on
pressure gradient.
CO2 carries oil into
the rock (bad).
and CO2 swelling pushes oil
out of the rock (good).
or
Step 3
As CO2 permeates
into the rock, oil
migrates to bulk CO2
in fractures based on
swelling and lower
viscosity.
Step 4
CO2 pressures equalize
inside of rock.
 Oil production is now
based only on
concentration gradient
driven diffusion.
 Oil in bulk CO2 is
swept through
fractures to production
well.
Extraction of Source and Reservoir Rock,110 C
ca. 3X9X9 mm chicklets
ca. 9X9X30 mm sq. rods
ca. 10 mm dia rod
Sample rocks are from two thermally-mature
areas of the Bakken and one conventional
reservoir.
Conventional reservoir: 25% porosity, ca, 1000
millidarcies permeability.
Middle Bakken has ca. 4.5-8.1% porosity,
0.002 to 0.04 millidarcies (Kurtoglu, 2013)
Upper and lower Bakken, much lower permeability
than middle Bakken.
Supercritical Fluid Extraction (SFE)
pump
5000 psi (34.5 Mpa) CO2
(Isco 260D)
6000 psi CH4
rock core
6 to 10 g. rock
sample cell
110 oC (230 F)
(heated)
flow control
extract
collection
1.3 mL/min liquid CO2 ,
3. 3 mL/min CH4
10 mL solvent
(acetone, CH2Cl2)
Experimental Procedures
The rock is exposed to 5000 psi CO2 (6000 psi CH4 and
CH4/ethane), with no outlet flow for 50 minutes (or up to
24 hours), then swept with fresh CO2 to collect
hydrocarbons for 10 min (ca. 2 cell void volumes).
Extracts are analyzed by GC/FID, residue is crushed
and solvent extracted to determine unrecovered oil.
“Conventional” reservoir 1‐cm rod, static mode
5‐6 hour extraction
Final Residue
C36
C7
Retention Time (Minutes)
FID Response
FID Response
Middle Bakken, 1‐cm rod, static mode
Final Residue
C7
Bulk Bakken Crude Oil
FID Response
FID Response
C36
Lower Bakken, 1‐cm rod, static mode
Final Residue
FID Response
FID Response
C7
C36
CO2 oil recovery from upper, middle, and lower
Bakken from the one well (24 h).
Conv. 1-cm rod
Low Bak, <3.5 mm
Up Bak, <3.5 mm
Mid Bak, 1-cm rod
Up Bak, 1-cm rod
Low Bak, 1-cm rod
CO2 oil recovery from upper, middle, and lower
Bakken from one well (1st 8 hours).
Conv. 1-cm rod
Low Bak, <3.5 mm
Up Bak, <3.5 mm
Mid Bak, 1-cm rod
Up Bak, 1-cm rod
Low Bak, 1-cm rod
So, you can get oil out of Bakken
rock with CO2, but what about
associated gas?
Middle Bakken, 11 mm round rod, 85/15 CH4/Et extraction (static)
Final Residue
4-6 hour extraction
FID Response
FID Response
2-4 hour extraction
1-2 hour extraction
0-1 hour extraction
72-96 hour
extraction
48-72 hour
extraction
24-48 hour
extraction
8-24 hour extraction
C7
Bulk Bakken Crude
Oil
C34
6-8 hour extraction
Lower Bakken, 11mm round rod, 85/15 CH4/Et (static)
Final Residue
4-6 hour extraction
72-96 hour
extraction
FID Response
FID Response
2-4 hour extraction
1-2 hour extraction
0-1 hour extraction
48-72 hour
extraction
24-48 hour
extraction
8-24 hour extraction
C7
Bulk Bakken Crude
Oil
C34
6-8 hour extraction
Upper Bakken, 11 mm round rod, 85/15 CH4/Et extraction (static)
Final Residue
FID Response
FID Response
C7
Bulk Bakken Crude Oil
C34
Oil is efficiently recovered from Middle Bakken
11 mm Round Rods, CO2 vs CH4 and 15% Et‐CH4
100%
90%
80%
Conventional, CO2
Mid Bakken, CO2
Mid Bakken, 85/15 CH4/Et
Mid Bakken, CH4
% of total HC
70%
60%
50%
40%
30%
20%
10%
0%
0
10
20
30
40
50
60
exposure time, hours
70
80
90
100
11 mm Round Rods, CO2 vs CH4 and 15% Ethane‐CH4
Conventional, CO2
Mid Bakken, CO2
Mid Bakken, CH4
100%
90%
80%
% of total HC
70%
60%
50%
40%
30%
20%
10%
0%
0
2
4
6
8
10
Thermal desorption contributes to HC
recovery, but is not primary.
11 mm Round Rods, CO2, CH4, 15% Ethane‐CH4, N2
100%
90%
Conventional, CO2
Mid Bakken, CO2
Mid Bakken, CH4
Mid Bakken, N2
80%
% of total HC
70%
60%
50%
40%
30%
6000 psi N2
20%
10%
0%
0
10
20
30
40
50
60
70
80
90
100
Hydrocarbon Recovery using CH4 and CO2, 11 mm Round Rods, Upper, Middle, and Lower Bakken
120%
CO2 middle
CH4 middle
100%
% of total HC
80%
CO2 lower
60%
CH4 upper
CH4 lower
CO2 upper
40%
20%
0%
0
10
20
30
40
50
60
70
80
90
100
Lower Bakken, 11 mm Round Rods, CO2, CH4, 15% Ethane‐CH4, N2
100%
90%
80%
% of total HC
70%
CO2
60%
CH4/Et
50%
40%
CH4
30%
20%
N2
10%
0%
0
10
20
30
40
50
60
70
80
90
100
Smaller rock sizes increase rate of oil recovery.
Lower Bakken, 11 mm rods vs 2‐3 mm chicklets, CO2 and CH4
100%
90%
CO2, chicklets
CH4, chicklets
80%
70%
% of total HC
CO2, rd rod
60%
50%
CH4, rd rod
40%
30%
20%
10%
0%
0
10
20
30
40
50
60
70
80
90
100
100%
Upper Bakken Shale, CO2
90%
Both CO2 and CH4/Et
recovery favor lighter
hydrocarbons, but CH4/Et
favors them more.
sum C #
7
9
10
12
15
17
20
70%
60%
50%
40%
30%
20%
10%
0%
0
20
40
60
80
100
CO2 exposure time, hours
100%
Upper Bakken Shale, 85/15 CH4/Et
90%
80%
% of total HC
% of total HC
80%
sum C #
7
9
10
12
15
17
20
70%
60%
50%
40%
30%
20%
10%
0%
0
20
40
60
80
85/15 CH4/Et exposure time, hours
100
Contact time is more important than CO2 volume.
75 g CO2
19 g CO2
6 g CO2
So—can we take these lab results and make
them useful to reservoir models? (big question!)
Simple two-site exponential model
2-site Empirical Model Fit to Experimental Data
F = 0.54
k1 = 4.5 hr -1
k2 = 1.2 hr -1
F = 0.13
k1 = 0.6 hr -1
k2 = 0.02 hr -1
F = 0.50
k1 = 1.7 hr -1
k2 = 0.1 hr -1
F = 0.15
k1 = 0.5 hr -1
k2 = 0.01 hr -1
Observations on mechanisms of
associated gas and CO2 EOR in Bakken
1. The experimental design is successful for studying the injected CO2 or
associated gas flowing “around” the rock rather than “through” the rock—
and results to date support the proposed mechanisms for EOR in
unconventional reservoirs.
2. The strong preference for low MW (more volatile) hydrocarbons
demonstrates that hydrocarbon mobilization into CO2 (and associated
gas) is the primary production mechanism, not CO2 dissolution into the
bulk oil.
3. The unexpectedly high recoveries using CH4 and CH4/ethane indicate
that thermal desorption may be important, but the nitrogen results show
it’s of minimal importance.
4. Exponential decay in recovery rates with time, and the large effect of
particle size show a mass-transfer limited recovery process.
Summary of Observations and Conclusions
1. CO2 and associated gas are capable of mobilizing oil from upper,
middle and lower Bakken (thermodynamics are favorable), but
we need to work on increasing the rate (kinetics) of the recovery
processes.
2. MMPs are higher for methane than CO2, but are still within
Bakken pressures.
3. Since most of the oil can be extracted from 1-cm rods, even
upper and lower Bakken shales have sufficient connectivity to be
accessed by CO2 and associated gas.
4. All samples show an initial “fast” recovery of ca. 20-70% of the
oil, followed by an exponential decline.
5. Oil recovery is mass transfer limited—enhanced by contact time
and more exposed rock surface area.
Since even a 1% incremental recovery is huge, perhaps research
should focus on the first few percent of the recovery curve?
Questions?
Thank you!
The authors thank Basak Kurtoglu (Marathon Oil) and the
North Dakota Geological Survey for providing the samples
used in these investigations. Financial support from the U.S.
Department of Energy, National Energy Technology
Laboratories (NETL) and the North Dakota Oil and Gas
Research Council are also gratefully acknowledged.
Please stop by to see us at Booth 1208 for
more information!
Energy & Environmental Research Center
University of North Dakota
15 North 23rd Street, Stop 9018
Grand Forks, ND 58202-9018
World Wide Web: www.undeerc.org
Telephone No. (701) 777-5256
Fax No. (701) 777-5181
Dr. Steven Hawthorne, Senior Research Manager
[email protected]
What might happen after we get oil into
the bulk CO2?
The hypothetical steps just discussed address
transporting the oil in the rock matrix to the bulk CO2 in
the fractures.
What about subsequent production/recovery steps?
Is MMP sufficient CO2 pressure to ensure oil recovery?
Does anything interesting happen
above and below MMP?
Bakken crude/CO2
behavior, 110 oC
CO2 pressure
increased from
ambient to 5000 psi,
then reduced back to
ambient.
Bakken Crude Oil
110 oC (230 F)
MMP = 2800 psi
© Energy and
Environmental
Research
Center, 2013
Does anything interesting happen
above and below MMP?
Conventional crude/CO2 behavior, 42 oC
CO2 pressure increased from ambient to 2300
psi, then reduced back to ambient.
© Energy and
Environmental
Research
Center, 2013

Laboratory Comparisons of CO2 and Rich Gas Injection on Oil

Transcription

Similar documents

Rebekka Bakken - C Major Entertainment

Meeting Agenda - Kubiak Research Group

SOS 2015 DECK.key - Shale Play Water Management

Energy and CO

Aubade

How fossil fuels are formed

It`s more than just cow farts METHANE:

project poster - Joint Institute for Strategic Energy Analysis

Binary Stream Gas Analyser

Presentation - Harvard University