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Studies of Reservoir Rock Wettability and Low Salinity Waterflooding
Sheena XieEnhanced Oil Recovery Institute
University of WyomingDenver, Colorado
January 15, 2009
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Project personnelNorm Morrow, Carol Robinson, Sheena (Xina) Xie, Li Yu Nina Loahardjo, Siluni Wickramathilaka, Hu Pui, Wei Wang (students)
Ron Borgialli, George Twitchell (Machine shop)
Ligang Yu, Xuanqi Zhang (visiting professors)
Jill Buckley, Geoff Mason, Koichi Takamura (adjunct professors)
CollaborationPegui Yin, Shaochang Wo, et al. (EORI staff)Mark Knackstedt (Australian National University rock physics group)Arne Graue (U. of Bergen)Doug Ruth (U. of Manitoba)
EORI and company supportEnhance Oil Recovery Institute, University of WyomingIndustry: ARAMCO*,BP*,Chevron, ConocoPhillips, Shell, StatoilHydro*, Total*, INL* includes provision of reservoir rock and crude oil
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Recent Publications Low salinity/cyclic flooding/spontaneous imbibition
Society of Core Analysts, Calgary, 2007J. Coll. Int. Sci. 2007aAm. Soc. Min. and Reclam., Gillette, 2007. SPE, ATCE, Anaheim, 2007Trans. in Porous Media, 2007SPE REE, 2007SPE IOR, Tulsa, 2008 SPE REE, 2008Int. Symp. Res. Wettability, Abu Dhabi, 2008 Trans. in Porous Media, in press 2009aSPE REE, in press, 2009 Trans. in Porous Media, in press, 2009bJPSE in press, 2007Langmuir, in press, 2009
Papers can be downloaded from: http://wwweng.uwyo.edu/economic/psc/
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Ongoing Projects
Reservoir Rock Wettability Studies –◊
evaluate reservoir rock wettability
◊
chemical stimulation to improve oil recovery Low Salinity Waterflooding
◊
Wyoming reservoirs ◊
rocks and oils provided by oil companies
◊
cyclic waterflooding
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Reservoir rock wettability studies –vital to all EOR processes◊
Evaluation of reservoir rock wettability♣
Muddy sandstone from the Grieve Field♣
Hatfield sandstone♣
Other crude oil/brine/rock combinations as needed◊
Chemical stimulation to improve recovery by
spontaneous imbibition from fractured reservoirs
♣
Tensleep reservoir rock oil recovery ♣
Cottonwood Creek reservoir rock oil recovery◊
Removal of water blocks ♣
Wamsutter tight gas deliverability
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Spontaneous imbibition
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0
20
40
60
80
100
1 10 100 1000 10000 100000
Oil
reco
very
, %
Dimensionless imbibition time
very strongly water-wet
F-A 6827F-A 6960F-A 6515F-A 6972
0
20
40
60
80
100
1 10 100 1000 10000 100000
Oil
reco
very
, %
Dimensionless imbibition time
very strongly water-wet
F-C/B F-C/B F-C/B F-C/B
Spontaneous imbibition - Grieve muddy sandstone/crude oil/formation brine (2177 ppm) –Used to estimate initial water saturation prior to CO2 injection
Permeability < 1 md Permeability < 1 md
Wettability of Grieve Field Sandstone
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0
20
40
60
80
100
1 10 100 1000 10000 100000
Oil recovery, %
OOIP
Dimensionless Imbibition time
#6073, Phi = 5.9%
#5952, Phi = 2.9%
#6095, Phi = 3.4%
#5839, Phi = 1.3%
VSWW
Strongly water‐wet curve
Spontaneous imbibition of Hatfield reservoir rock/crude oil/Tensleep formation brine in Hatfield (5590 ppm) – Reservoir response better to low pump rate, concluded that imbibition is the main production mechanism for this low permeability fractured reservoir
Hatfield Sandstone
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Tensleep Sandstone – Crude oil recovery by spontaneous imbibition
Cores from a dry well (water saturated) Cores from an oil well
0
10
20
30
40
50
60
0 20 40 60 80 100 120 140 160
Oil recovery, %
OOIP
Imbibition time, day
5501B
5501A
0
10
20
30
40
50
60
0 5 10 15 20 25
Oil
rec
ove
ry,
%O
OIP
Imbibition time, day
T1AT1CT2BT2C
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Surfactant enhanced imbibition –Surfactant screening*
Compatibility with formation/injected brine salinityCompatibility at reservoir temperature
Rock types: Tensleep sandstoneCottonwood Creek dolomite
* Surfactants provided by Stepan, AkzoNobel Help from Dr. George Hirasaki and his group
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Tensleep formation water solutions
RatioSurfactant +
Co‐Surfactant
Precipitation @
Room Temp.
Precipitation
@ 75 0C
1 to 1 A1+C8 Y YA1+C1 N YS3A+S2 Y YS3A+C1 Y YS1+S2 Y YS1+C1 Y YS1+C3 Y Y
B. PAS‐8S+S3A Y YT91‐8+S3A Y YT91‐8+S2 Y Y
3 to 1 S3A+S2 N YS3A+C1 N YS1+S2 N Y
B. PAS‐8S+S3A Y YT91‐8+S3A Y Y
RatioSurfactant +
Co‐Surfactant
Precipitation
@ Room
Temp.
Precipitation
@ 75 0C
1 to 1 A1+C8 Y YA1+C1 N YS3A+S2 Y YS3A+C1 N YS1+S2 Y YS1+C1 Y YS1+C3 Y Y
B. PAS‐8S+S3A Y YT91‐8+S3A Y YT91‐8+S2 Y Y
3 to 1 S3A+S2 N YS3A+C1 N YS1+S2 N Y
B. PAS‐8S+S3A Y YT91‐8+S3A Y Y
2 wt.% Surfactant/ Co‐Surfactant, 2 wt.%
Co‐Solvent (DGBE), and 1 wt.% NaB(OH)4
1 wt.% Surfactant/ Co‐Surfactant, 2 wt.%
Co‐Solvent (DGBE), and 1 wt.% NaB(OH)4
Tensleep formation water: 3030 ppm (Ca + Mg = 340 ppm, HCO3 = 70 ppm)
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Cottonwood Creek formation water solutions
RatioSurfactant + Co‐
Surfactant
Precipitation @
Room Temp.
Precipitation
@ 75 0C
1 to 1 S1+C1 Y YS1+C3 Y Y
B. PAS‐8S+S3A Y YT91‐8+S2 Y YT91‐8+S3A Y YS1+S2 N Y
3 to 1 S1+S2 Y YT91‐8+S3A N Y
B. PAS‐8S+S3A Y Y
1 wt.% Surfactant/ Co‐Surfactant, 2 wt.%
Co‐Solvent (DGBE), and 1 wt.% NaB(OH)4
Cottonwood Creek formation water: 23,740 ppm (Ca + Mg = 4,000 ppm, HCO3 = 2,200 ppm)
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Tensleep Sandstone
Imbibition at reservoir temperature 75°C for cores from dry wells
0
10
20
30
40
0 10 20 30 40 50
Oil recovery, %
OOIP
Imbibition time, day
5517B: 168.4 md
Surfactant: Petrostep S1 (3000 ppm) + NaB(OH)4 (0.1 wt%)
5523A: 194.2 md
Formation brine imbibition
Surfactantimbibition
0
10
20
30
40
0 10 20 30 40 50
Oil recovery, %
OOIP
Imbibition time, day
5523E: 146.8 md
5517C: 130.6 md
Surfactant: Petrostep S2 (3000 ppm) + NaB(OH)4 (0.1 wt%)
Formation brine imbibition
Surfactantimbibition
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0
10
20
30
40
0 20 40 60 80
R, %
OO
IP
Imbibition time, day
Surfactant: T91-8
1T
2T
3T
4T
5T
6T
%5.22%,12,11:6
%0%,4.15,56:5
%1.13%,5.10,06.0:4
%3.1%,6.16,83:3
%0%,42.11,2.14:2
%89.31%,26.17,456:1
===
===
===
===
===
===
wig
wig
wig
wig
wig
wig
SmdkT
SmdkT
SmdkT
SmdkT
SmdkT
SmdkT
φ
φ
φ
φ
φ
φ
Surfactant enhanced imbibition - Cottonwood Creek Dolomite
60°C
Formation brine imbibition
Surfactant imbibition
In brine
In T91-8 solution
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Fundamentals of surfactant enhanced imbibition
◊
Surfactants interact with the adsorbed materials from the crude oil, resulting in the release of the adsorbed organic materials. The rock surface becomes less oil-wet and imbibition rate increased (effect of surfactant and adsorption on capillary driving forces on imbibition are being investigated in detail)
◊
Interfacial tension between oil and brine decrease (or increase in the Bond number) can contribute to improved oil recovery through gravity segregation.
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Objective: Evaluate the potential of low salinity waterflooding for Tensleep* and Cottonwood** Creek reservoirs using CBM water composition
*Minnelusa is the most prolific producer in Wyoming and has comparableorigin and mineralogy to the Tensleep
**Estimated that only about 10% of the oil in the Cottonwood Creek reservoirhas been produced
Low Salinity Waterflooding -Disposal of coal bed methane (CBM) water and improved recovery from Wyoming reservoirs
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0
20
40
60
80
100
0 5 10 15 20 25 30 35Brine injected, PV
R f, %
OO
IP
0
5
10
15
Δ P, p
si
Test A:R1/C1WP crude oil, Swi = 40.6%q = 2.6 ft/D
RIB(29,690 ppm)
R
ΔP
0
20
40
60
80
100
0 5 10 15 20 25 30 35Brine injected, PV
R f, %
OO
IP
0
5
10
15
ΔP, p
si
WP crude oil, Swi = 40.6%
RIB(29,690 ppm)
R
ΔP
LSB(1,480 ppm)
16.2%
0
20
40
60
80
100
0 10 20 30 40 50 60Brine injected, PV
Rf,
%O
OIP
0
5
10
15
ΔP, p
si
LC crude oil, Swi = 13.6% (LSB)
R
ΔP
RIB(29,690 ppm)
NaCl(8,000 ppm)
NaCl(1,500 ppm)
12.7%
LSB(1,480 ppm)
4%Divalent ions
removedSalinity
decreased Divalent ions
added
Low salinity waterflooding to improve oil recovery
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CBM water Underground Injection Control: Class V restrictions
CBM water for oil and gas recovery: Class II (less restricted disposal)
Typical PRB CBM water: TDS ~ 1,800 ppmSAR (sodium adsorption ratio) ~ 25
Unsuitable for irrigation or surface discharge when: TDS > 3,000 mg/LSAR > 8
Wyoming CBM water disposal
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Imbibition tests show Tensleep cores are very weakly water-wet
0
20
40
60
80
100
1.E+00 1.E+02 1.E+04 1.E+06 1.E+08 1.E+10
R, %
OO
IP
Dimensionless imbibition time
E2
VSWW (Ma et al., 1997)
1000 μm
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0
10
20
30
40
50
60
70
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30 35
Pre
ssur
e D
rop,
psi
Rec
over
y,%
Injected PV
CBM Brine1316ppm
T8104Swi=21.03%
+7.18%
Tensleep Brine3030ppm
Waterflooding of Tensleep brine followed by CBM water• Example of improved recovery from cores with very low clay content• Movement of dolomite was observed at ANU in real time micro-CT imaging• Tensleep rock properties: ongoing work
Kg = 20.7 mdφ
= 14.2%
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0
5
10
15
20
25
30
35
40
45
0102030405060708090
100
0 5 10 15 20 25 30 35 40
Pre
ssur
e D
rop,
psi
Rec
over
y, %
OO
IP
Brine Injected, PV
Tensleep H5Swi=18.62%
Recovery
Pressure
+4.57%
Waterflooding with Tensleep brine followed by CBM water
Tensleep brine3030 ppm
CBM water1316 ppm
Kg = 23.2 mdφ
= 8.8%
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Results are in the range reported by BP for 18 tests on clastic rocks but response to salinity change for the Tensleep is generally slower (2%+ in oil recovery)
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Spontaneous imbibition tests on Cottonwood dolomite /crude oil show cores are very weakly water wet
0
10
20
30
40
0 2 4 6 8 10 12
R, %
OO
IP
Imbibition time, day
1T
2T 3T4T
5T6T
%5.22%,12,11:6%0%,4.15,56:5
%1.13%,5.10,06.0:4
%3.1%,6.16,83:3%0%,42.11,2.14:2
%89.31%,26.17,456:1
===
===
===
===
===
===
wig
wig
wig
wig
wig
wig
SmdkTSmdkT
SmdkT
SmdkTSmdkT
SmdkT
φ
φ
φ
φ
φ
φ
Width = 132 μm
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0
1
2
3
4
5
6
7
8
9
10
0
10
20
30
40
50
60
70
80
90
100
0 3 6 9 12 15 18 21 24 27
Pre
ssur
e D
rop,
psi
Rec
over
y, %
OO
IP
Injected Volume, PV
30,755ppm 1,537ppm
Recovery
Pressure
+6.41%
Cottonwood 5800ASwi=48.89%
Waterflooding of Core 5800AFirst example of response to low salinity for dolomite
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Waterflooding of Cottonwood dolomite Core 5800B
0
2
4
6
8
10
12
14
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30 35
Pre
ssur
e D
rop
, psi
Rec
ove
ry, %
OO
IP
Injected Volume, PV
30,755ppm 1,537ppm
Recovery
PressureCottonwood 5800BSwi=36.27%
+6.79%
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Cyclic water flooding
Unexpected high recoveries for high salinity brine after exposure to low salinity brine lead to investigation of reproducibility of waterfloods for high salinity brine. (No data has been reported previously on this topic.)
Recoveries of crude oil for several rock types (reservoir sandstone, outcrop sandstone and outcrop carbonate) showed consistent trends of increase in recovery from one cycle* to the next.
* waterflooding and restoration to initial water saturation
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Cyclic Waterflooding
Recovery of mineral oil Recovery of crude oil from a reservoir sandstone (same trends of increase in recovery wereobtained for outcrop sandstone and carbonate)
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Cyclic flooding showed systematic increase in oil recovery.*
However, material balance after a few cycles was not satisfactory.
Now applying tracer test to provide independent check on residual oil and initial water saturations.***provisional patent filed
**with the help of Charlie Carlisle and co-workers
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Ongoing work
• Rock and crude oil characterization• Testing of reservoir rocks and oil samples
supplied by EORI and Companies• Unconsolidated reservoir sands – laboratorytechniques
• Joint UW/Australia National University projecton fundamentals of oil recovery
♣
Distribution of connate water and residual oil in mixed-wet Tensleep rocks by micro X-ray CT imaging;
♣
Effect of brine (specific ions) on silica/carbonate interactions fromatomic force measurements;
♣
Plasma cleaning: a) limitations on size of cores, b) application to cleaning cores exposed to oil base mud.
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Ongoing work continued …
Application of surfactants to improved oil recovery from fractured reservoirs by spontaneous imbibition.
Extend fundamental studies of imbibition to effects of salinity and mixed-wet imbibition (includes joint work with U. Bergen using radioactive tracers to monitor saturations during imbibition)
Tight gas sands - removal and prevention of water blocks – Wamsutter cores (joint with INL)
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Thanks !
Questions?
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Dissolution of Middle-eastcarbonate
0.0
50.0
100.0
150.0
200.0
250.0
300.0
0 5 10 15 20
Ion concen
tration, ppm
PV injected
SO4
Mg
Ca
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
900.0
1000.0
0 5 10 15 20
Ion concen
tration, ppm
PV injected
SO4
Mg
Ca
Carbonate core saturated with 2883 ppm NaCl and displaced with the same brine
Carbonate core saturated with 57654 ppm NaCl and displaced first with the same brine and then with 2883 ppmbrine
Hide: mention ongoing workof Cottonwood carbonate
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700
0
100
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900
0 10 20 30 40 50 60 70 80
EtA
c C
once
ntra
tion
(ppm
)
MeO
H C
once
ntra
tion
(ppm
)
Volume Produced (mL)
Tracer Concentration vs. Volume Produced
Berea sandstone
Tracer test to verify water content
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0
20
40
60
80
100
0 20 40 60 80
Oil
Rec
over
y, %
OO
IP
Brine Injected (PV)
OOIP
E-10 : R1/C3Swi = 18.39 %
29,000 ppm20,000 ppm15,000 ppm7,000 ppm5,000 ppm4,000 ppm3,000 ppm1,000 ppm
Gradual salinity increase for waterflooding
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Constant pressure flooding, no extra oil recovery
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100
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0 10 20 30 40
pH o
r Pre
ssur
e D
rop,
psi
Oil
Rec
over
y, %
OO
IP
time, hours
pH
ΔP
R
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Minelusa Oil
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15
20
25
30
35
0 2 4 6 8 10 12 14
pH
IFT
[mN
/m]
0.01 [M]
0.1 [M]
1 [M]
0
5
10
15
20
25
30
35
0 2 4 6 8 10 12 14pH
IFT
[mN
/m]
0.01 [M]
0.1 [M]
1 [M]
Cotton Wood
Effect of salinity and pH on interfacial tensions
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BEAKER
PRESSURE TRANSDUCER
BRINE
VOLT METER
CLOSED FUNNEL
OIL
CORE
Effect of surfactant on imbibition back pressure
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100
t (hours)
Qo/Vφ
xf/Lc
0
2
4
6
8
10
Pend
(kPa)fab
Qo
/Vφ
Tested core: IS1
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100
t (hours)
Qo/Vφ
xf/Lc
0
2
4
6
8
10
Pend
(kPa)
Pend
xf/Lc
Qo/Vφ
fab
Liquid changed
Brine imbibition alone
Brine imbibition to almost half way along the core; then switched to surfactant Imbibition