EOR by “Smart Water” Why ???
EOR by “Smart Water”Why ???Why ???
Outline
• Background– Wettability
• Capillary pressure curve• Relative permeability of oil and water
• “Smart Water” in Carbonates– Chemical mechanism– Chemical mechanism– EOR-potential
• “Smart Water” in Sandstones– Chemical mechanism – EOR-potential
Research direction
• Water based EOR by “Smart Water”
– How to optimize the ion composition of injection water to promote wettability alteration to improve oil recovery by water flooding.flooding.
– Detailed knowledge about the chemical mechanism in order to be able to evaluate actual field candidates for “smart” water.
– Carbonates and Sandstones
What is “Smart Water”?
• “Smart water” can improve initial wetting properties of the reservoir and optimise fluid flow/oil recovery in porous medium during production.
• “Smart water” can be made by modifying the ion composition. No expensive chemicals are added.composition. No expensive chemicals are added.
• Wetting condition dictates– Capillary pressure curve; Pc=f(Sw)– Relative permeability; ko and kw = f(Sw)
Wetting properties in carbonates
• Carboxylic acids, R-COOH– AN (mgKOH/g)
• Bases (minor importance)– BN (mgKOH/g)
• Charge on interfaces
- - - -
+ + + + + + +
- - - -
+ + + + + + +
Ca2+ Ca2+ Ca2+
• Charge on interfaces– Oil-Water
• R-COO-
– Water-Rock• Potential determining ions
– Ca2+, Mg2+, SO42-, CO3
2-
, pH
- - - -
- - - - -SO4
2- SO42- SO4
2-
Spontaneous imbibition into chalk
Imbibition temperature 40 °C
50
60
70
80
Oil
prod
uctio
n, %
OO
IP
Oil A. AN=0, Test 1
0
10
20
30
40
50
1 10 100 1000 10000 100000 1000000
Time, min.
Oil
prod
uctio
n, %
OO
IP
Oil A. AN=0, Test 1
Oil D. AN=0.055, Test 7
Oil B. AN=0.06, Test 5
Oil E. AN= 0.41, Test 8
Oil C. AN=0.52, Test 6
Oil F. AN=1.73, Test 9
Wettability alterationStandnes and Austad, J. Pet. Sci Eng. 28 (2000) 123-143
Cationic surfactant: n-C 12N(CH3)3Br termed C12TAB• Chalk: 2 mD, T=40 oC• Oil: AN=1.0 mgKOH/g
Imbibition temperature 40 °C
0
10
20
30
40
50
60
70
0 20 40 60 80 100 120Time, days
Oil
prod
uctio
n, %
OO
IP
C12TAB, Test 1
C12TAB, Test 2
C12TAB, Test 4
Brine, Test 3
Can SW change wetting conditions of Chalk ??
• SO42- was important as a catalyst for
wettability alteration by C12TAB.– The efficiency increased as the temperature
increasedincreased
• Can seawater act as a wettability modifier at high temperature without using expensive surfactants ???!
Question:
• Why is injection of seawater such a tremendous success in the Ekofisk field??– Highly fractured– High temperature, 130 oC.– Low matrix permeability, 1 -2 mD– Low matrix permeability, 1 -2 mD– Wettability:
• Tor-formation: Preferential water-wet• Lower Ekofisk: Low water-wetness• Upper Ekofisk: Neutral to oil-wet
Oil recovery prognoses
400
OIL
RA
TE
, MS
TB
D (
GR
OS
S)
2001: Goal: 46%
NPD;2002: 50%
0
1972
1976
1980
1984
1988
1992
1996
2000
2004
2008
2012
2016
2020
2024
2028
OIL
RA
TE
, MS
TB
D (
GR
OS
S)
OOIP∼∼∼∼18 %
OOIP∼∼∼∼46 %
2007: Goal 55 %
Model brine compositionComp. Ekofisk Seawater
(mole/l) (mole/l)Na+ 0.685 0.450K+ 0 0.010Mg2+ 0.025 0.045Ca2+ 0.231 0.013Ca 0.231 0.013Cl- 1.197 0.528HCO3
- 0 0.002SO4
2- 0 0.024
Seawater: [SO42-]~2 [Ca2+] and [Mg2+]~ 2 [SO4
2-]
[Mg2+]~4 [Ca2+]
Effects of Sulfate and T
100 oC 130 oC
• Crude oil: AN=2.0 mgKOH/g•Initial brine: EF-water•Imbibing fluid: Modified SSW
0.0
10.0
20.0
30.0
40.0
50.0
0 5 10 15 20 25 30 35 40 45
Time (days)
Rec
over
y (%
OO
IP)
CS100-5 - SSW*4S
CS100-2 - SSW*3S
CS100-4 - SSW*2S
CS100-1 - SSW
CS100-3 - SSW/2S
CS100-6 - SSW/US
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
0 2 4 6 8 10 12 14
Time (days)
Rec
ove
ry (
%O
OIP
)
CS3-1 - SSW*4S
CS3-2 - SSW*2S
CS3-8 - SSW*2S
CS3-3 - SSW
CS3-4 - SSW/2S
CS3-5 - SSW/US
Parallel tests!
Sulfate adsorption-Temp. effects
0.75
1.00
C/Co SCN FL#7-1 SSW-M at 21°C A=0.174
C/Co SO4 FL#7-1 SSW-M at 21°C
�Chromatographic separation of SCN- and SO42-
0.00
0.25
0.50
0.75
0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2PV
C/C
o
C/Co SO4 FL#7-1 SSW-M at 21°C
C/Co SCN FL#7-2 SSW-M at 40°C A=0.199
C/Co SO4 FL#7-2 SSW-M at 40°C
C/Co SCN FL#7-3 at 70°C A=0.297
C/Co SO4 FL#7-3 at 70°C
C/Co SCN FL#7-4 at 100°C A=0.402
C/Co SO4 FL#7-4 at 100°C
C/Co SCN FL#7-5 at 130°C A=0.547*(Extrapolert2.6PV)C/Co SO4 FL#7-5 at 130°C
Is Ca2+ active in the wettability alteration??
• Crude oil: AN=0.55 mgKOH/g• Swi = 0; Imbibing fluid: Modified SSW• Temperature: 70 oC
60.0
70.0
Oil
reco
very
(%
OO
IP)
0.0
10.0
20.0
30.0
40.0
50.0
0.0 10.0 20.0 30.0 40.0 50.0 60.0
Time (day)
Oil
reco
very
(%
OO
IP)
CS100-1 - SSW*4Ca
CS100-2 - SSW*3Ca
CS100-3 - SSW
CS100-4 - SSW/2Ca
CS100-5 - SSW/UCa
Affinities of Ca 2+ and Mg 2+ towards the chalk surface
0.75
1.00
C/Co SCN (Brine with Mg andCa2+) at 23C [Magnesium] 1.25
1.50
1.75
2.00
T=20 oC T=130 oC
•NaCl-brine,[Ca 2+]= [Mg 2+]= 0.013 mole/l
0.00
0.25
0.50
0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6PV
C/C
o
Ca2+) at 23C [Magnesium] A=0.084C/Co Mg2+ (Brine with Mg2+and Ca2+) at 23°C
C/Co Ca2+ (Brine with Mg2+and Ca2+) at 23°C
0.00
0.25
0.50
0.75
1.00
1.25
0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0PVC
/Co
C/Co SCN (Brine with Mg and Ca2+)at 130°C
C/Co Mg2+ (Brine with Mg2+ andCa2+) at 130°C
C/Co Ca2+ (Brine with Mg2+ andCa2+) at 130°C
CaCO3(s) + Mg 2+ = MgCO3(s) + Ca2+
Effects of potential determining ions on spontaneous imbibition
Imbibition at 70 & 100 oC (with/without Ca & Mg)
40
60
Rec
over
y, %
OIIP
25:SWx0CaMg(+Mg@43days)
26:SWx0Sx0CaMg(+Mg@ 53 days)
27:SWx2Sx0CaMg(+Ca@43 days)
28:SWx4Sx0CaMg(+Mg@53 days)
0
20
40
0 20 40 60 80 100 120Time, days
Rec
over
y, %
OIIP
70°C
100°C 130°C
Suggested wettability mechanism
High T
Test by BP on Valhall(Webb et al. IPTC 10506, Doha, 2005)
• Complete reservoir conditions, Tres=90 oC• Oil recovery using FW and SW
– Imbibition at Pc=0: FW: 22.4 %PV and SW: 31 %PV; 40% increase– Forces imbibition at Pc=-1 psi: FW: ~45%PV and SW: ~60%PV
Flow conditions
• Fractured vs. non-fractured reservoir– Spontaneous imbibition– Forced imbibition
• What is the efficiency of “Smart Water” • What is the efficiency of “Smart Water” ???
Spontaneous vs. forced imbibition
90 oC
110 oC 120 oC
Environmental aspects
• Can PW water be co-injected with SW and still act as a “Smart” EOR-fluid ???– Compatibility between SW and PW
• Precipitation of CaSO4, SrSO4, and BaSO4• Precipitation of CaSO4, SrSO4, and BaSO4
Mixtures of PW with SW at 110 oC
40
50
60
70R
ecov
ery
(%O
OIP
)
0
10
20
30
0 10 20 30 40 50Time (Days)
Rec
over
y (%
OO
IP)
SI PW1SSW8
SI PW1SSW2
SI PW1SSW1
SI PW
"FI PW"
"FI SSW"
Crude oil: AN = 1.9 mgKOH/g. Chalk
”Smart Seawater” in Chalk
110 oC 120 oC
50%
60%
70%
80%
Re
co
ve
ry F
acto
r (%
OO
IP
)
40%
50%
60%
70%
80%
Re
co
ve
ry F
acto
r (%
OO
IP
)
0%
10%
20%
30%
40%
0 10 20 30 40 50 60 70
Time (days)
Re
co
ve
ry F
acto
r (%
OO
IP
)
SSW SSW0NaCl Dil SSW 20000 Dil SSW 10000
Fig. 3. Spontaneous imbibition at 110 ºC
0%
10%
20%
30%
0 5 10 15 20 25 30 35
Time (days)
Re
co
ve
ry F
acto
r (%
OO
IP
)
SSW SSW0NaCl DilSSW 1600
DilSSW 1600 SSW4NaCl
Fig. 4. Spontaneous imbibition at 120 ºC using different imbibing fluids with different salinities and ionic composition.
EOR-potential by ”Smart Seawater” (depleted in NaCl) in Ekofisk may increase recovery by 10 % of OOIP: Money .. Money !!!!!
Forced Imbibition
• Smart SW in a tertiary process
50%
60%
70%
80%
Re
co
ve
ry F
acto
r %
0%
10%
20%
30%
40%
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00
PV Injected (ml)
Re
co
ve
ry F
acto
r %
F.W. SSW SSW0NaCl
Fig. 11. Forced Displacement at 120ºC at the rate of 1.0 PV/day; forced displacement by formation brine, seawater and seawater without NaCl
Low Salinity
0.3
0.4
0.5
0.6
0.7
Oil
Pro
duct
ion
(Tot
al P
ore
Vol
ume)
0.535 PV
0.61 PV
N. Morrow and later BP
0
0.1
0.2
0 5 10 15 20 25 30
Water Throughput (Pore Volumes)
Oil
Pro
duct
ion
(Tot
al P
ore
Vol
ume)
High Salinity Low Salinity(15,000 ppm) (1,500 ppm)
By: Webb et al. 2005.(By: Larger et al. 2007)
The average LowSal effect is ~14 %
Important parameters
• Initial wetting– Clay
• Different clays have different pH range for optimum adsorption
– Initial FB
• LowSal fluid– Composition
• Less important ?• Low ionic strength
important• Gradient in active ions– Initial FB
• Divalent vs. mono valent ions, important ??
• pH~5 (dissolved CO2)– Crude oil
• BN important• AN important
– Temperature• High and low T, OK
• Gradient in active ions– pH change
• Local increase in pH at the clay surface important ?
– Dynamic process• Flooding rate• Irreversible desorption
Suggested mechanisms
• Wettability modification towards more water-wet condition, generally accepted.
• Migration of fines (Tang and Morrow 1999).• Increase in pH lower IFT; type of alkaline flooding • Increase in pH lower IFT; type of alkaline flooding
(Mcguri et al. 2005). • Multicomponent Ion Exchange (MIE) (Lager et al.
2006).• Small changes in bulk pH can impose great
changes in Zeta-potential of the rock (StatoilHydro)• “Salting in” effects
Presentation linked to:
SPE 129767-PPChemical Mechanism of Low Salinity Water
Flooding in Sandstone ReservoirsFlooding in Sandstone Reservoirs
Tor Austad, Alireza RezaeiDoust and Tina Puntervold, University of Stavanger, 4036 Stavanger, Norway
This paper was prepared for presentation at the 2010 SPE Improved Oil Recovery Symposium held in Tulsa, Oklahoma, USA, 24–28 April 2010.
Is Low Sal effect a “salting in” effect ?Adsorption/desorption onto kaolinite
• Quinoline
1.50
2.00
2.50
mg
PTB
BA
ads
orbe
d / g
kao
linite
Ads isotherm
Desorption HS#1
Desorption HS#2
Desorption LS#1
~25000 ppm
~25000 ppm
~11200 ppm
pH ~6.3
pH ~5.4
• Carboxylic acid
1.50
2.00
2.50
mg
Qui
nolin
e ad
sorb
ed /
g ka
olin
ite
25000 ppm
16000 ppmpH ~5
11000 ppmpH ~5.27200 ppm
pH ~5.3
pH ~5
2200 ppmpH ~5.1
3100 ppmpH ~5.1
4900 ppmpH ~5.2
2000 ppmpH ~5.6
3000 ppmpH ~5.6
4900 ppmpH ~5.3
1100 ppmpH ~5.3
1000 ppmpH ~6.0
0.00
0.50
1.00
0.0000 0.0010 0.0020 0.0030 0.0040 0.0050 0.0060
Equilibrium [PTBBA], mol/l (M)
mg
PTB
BA
ads
orbe
d / g
kao
linite
Desorption LS#1
Desorption LS#2
~4600 ppm
~2300 ppm~1300 ppm
pH ~6.1
pH ~4.5
0.00
0.50
1.00
0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035
Equilibrium [Quinoline], mol/l (M)
mg
Qui
nolin
e ad
sorb
ed /
g ka
olin
ite
Ads isotherm
Desorption HS#1 pH adj
Desorption HS#2 pH adj
Desorption HS#3
Desorption HS#4
Desorption LS#1 pH adj
Desorption LS#2 pH adj
Desorption LS#3
Desorption LS#4
Suggested mechanismInitial situation Low salinity flooding Final situation
Clay
NH Ca2+
O
H
H
Clay
NH Ca2+
Clay
NCa2+
H+HO
H
Fig. 1. Proposed mechanism for low salinity EOR effects. Upper: Desorption of basic material. Lower: Desorption of acidic material. The initial pH at reservoir conditions may be in the range of 5.
C HO
H
Clay
Ca2+H+
R
HO
O H
OH
Clay
Ca2+
H+H+
R
O-
CO
Clay
Ca2+H+
R
HO
O C
Chemical equations
• Desorption of cations by low sal water– Clay-Ca2+ + H2O = Clay-H+ + Ca2+ + OH-
• Wettability alteration– Basic material– Basic material
• Clay-NHR3+ + OH- = Clay + R3N + H2O
• Acidic material• Clay-RCOOH + OH- = Clay + RCOO- + H2O
Adsorption of basic materialQuinoline
Kaolinite
Nonsweeling(1:1 Clay)
Burgos et al.
Evir. Eng. Sci.,
19, (2002) 59-68.
Montmorillonite
Swelling (2:1 clay, similar in structure to illite/mica)
Desorption of quinoline
Kaolinite
Burgos et al. Evir. Eng. Sci.,19, (2002) 59-68.
Montmorillonite
Adsorption reversibility by pH
5,00
6,00 Adsorption pH 5
Desorption pH 8-9
Readsorption pH 5.5
QuinolineSamples 1-6: 1000 ppm brine.Samples 7-12: 25000 ppm brine
0,00
1,00
2,00
3,00
4,00
5,00
0 5 10 15
Ads
orpt
ion
(mg/
g)
Sample no.
Readsorption pH 5.5
Desorption pH 2.5
What is the role of the acidic components ??
• Adsorption of benzoic acid onto kaolinite at 32 °C in a NaCl brine (Madsen and Lind, 1998)
pHinitial Γmax µmole/m2 µmole/m
5.3 3.7 6.0 1.2 8.1 0.1
Increase in pH increases water wetness.
No correlation between AN and LowSal effects has been detected (Larger et al.)
Acid – base properties similar
• BaseBH+ = H+ + BpKa=4.7
[ ][ ]B
BHpKpH a
+
+= lg [ ]B
•Acid
HA = H+ + A-
pKa = 4.9[ ]
[ ]B
BHpKpH a
+
+= lg
Fig 4. Supposed adsorption of R–COOH onto clay by H-bonding at pH 4-5. Analogue to a dimeric complex of carboxylic acid.
O C
Clay
H+
R
HO C
H
OR C
O
OR
H
O
Decrease in pH by CO 2 and H2S
5
6
7
8
pH
2
3
4
1.00E-10 1.00E-08 1.00E-06 1.00E-04 1.00E-02
mol added H2S or CO2
Varg H2SVarg CO2DW H2SDW CO2Seawater H2SSeawater CO2
Fig. 6. Simulated change in pH when CO 2 or H2S is dissolved into 200000 ppm Varg reservoir brine under pressure at 7 5 °C. Pressure was 100 atm to keep the gas in solution.
Important clay properties
Table 5 Properties of actual clay minerals (International Drilling Fluids (IDF), 1982)
Property Kaolinite Illite/Mica Montmorillonite Chlorite
Layers 1:1 2:1 2:1 2:1:1 Layers 1:1 2:1 2:1 2:1:1
Particle size (micron) 5-0.5 large sheets to 0.5 2-0.1 5-0.1
Cation exchange cap. (meq/100g)
3-15 10-40 80-150 10-40
Surface area BET-N2 (m2/g) 15-25 50-110 30-80 140
General order of affinity: Li+<Na+<K+<Mg2+<Ca2+<H+
Adsorption/desorption of cations
• Kaolinite and Chlorite– Non-swelling– Adsorption at edge surfaces– Great selectivity for Ca2+ over Na+– Great selectivity for Ca over Na– FW: significant amount of Ca2+ needed
• Illite/Mica and Montmorillonite/Smectite– Lattice substitutions are the main mechanism– Lower selectivity for Ca2+ over Na+
– FW: Low sal effect without Ca2+ possible ???
Optimal condition for low sal effect
• Balanced adsorption onto clay– Organic material– Cations
• Key process• Key process– Local increase in pH close to the clay-water
interface promoted by desorption of cations.
Salinity of Low Sal fluid
Desoroption
FWAds
orp
LS
Fig. 7 Probable/Typical adsorption isotherm of Ca2+ from high saline brine onto clay minerals of a reservoir rock at pH 4-8.
eq. conc. Ca2+
LS
Solubility of Mg(OH) 2 and Ca(OH)2 vs. pH
1E-061E-05
0.00010.001
0.010.1
1
mol
Mg2
+ or
Ca2
+
1E-111E-101E-091E-081E-071E-06
5 6 7 8 9 10 11 12 13 14
pH
mol
Mg2
+ or
Ca2
+
Mg2+ 50 °CMg2+ 100 °CCa2+ 50 °CCa2+ 100 °C
Fig. 10. Solubility of Mg(OH)2 and Ca(OH)2 versus p H at 50 and 100 oC in a 50 000 ppm NaCl brine and 6 bars.
Change in Mg 2+ can be related to precipitation of Mg(OH) 2
[Mg2+]mol/l
10-3
Fig. 11. Schematically change in Mg2+ concentration in the produced water during a low salinity flood. The concentration of Mg2+ is suggested to be quite similar for the initial FW and low saline brine.
pH>9pH≤ 8 pH≤ 8
Low Salinity
Outcrop material
• Minerals– Clay content
• Kaolinite 0 wt%• Chlorite 1.9 wt%• Chlorite 1.9 wt%• Illite 8.5 wt%
– Quartz ~57 wt%– Albite ~ 32 wt%– CaCO3 0.3 wt%
Brine and oil used
NaCl
(mole/l) CaCl2 .2H2O
(mole /l) KCl
(mole /l) MgCl2 .2H2O
(mole /l)
Connate Brine 1.54 0.09 0.0 0.0
Low Salinity Brine-1 0.0171 0.0 0.0 0.0
Low Salinity Brine-2 0.0034 0.0046 0.0 0.0
Low Salinity Brine-3 0.0 0.0 0.0171 0.0 Low Salinity Brine-3 0.0 0.0 0.0171 0.0
Low Salinity Brine-4 0.0034 0.0 0.0 0.0046
Total oil: AN=0.1 and BN=1.8 mgKOH/g
Res 40: AN=1.9 and BN=0.47 mgKOH/g
Effects if Low Sal brine composition
0
10
20
30
40
50
60
Rec
over
y (%
)
B15 - CaCl2 Brine
B14 - NaCl Brine
B16 - MgCl2 Brine
Total oil
0
0 2 4 6 8 10 12 14
PV Injected
0
20
40
60
80
100
0 2 4 6 8 10 12
Tho
usan
ds
Brine PV Injected
Sal
inity
(pp
m)
4
5
6
7
8
9
10
pH
B15-SalinityB14-SalinityB16-SalinityB15-pHB14-pHB16-pH
Effect of oil properties
40
50
60
Rec
over
y (%
)
0
10
20
30
0 2 4 6 8 10 12 14
PV Injection
Rec
over
y (%
)
B-15 TOATL Oil
B-11 Res-40 Oil
Lower initial pH by CO 2
Core No.
Swi %
TAging ° C
TFlooding ° C
Oil Low Salinity
Flood Formation Brine
B18 19.76 60 40
TOTAL Oil
Saturated With CO2
at 6 Bars
Low Salinity-1
NaCl 1000
ppm
TOTAL FW
B14 19.4 60 40 TOTAL Oil Low Salinity-1
NaCl 1000
ppm
TOTAL FW
80
Low Salinity
10
0
10
20
30
40
50
60
70
0 2 4 6 8 10 12 14 16
Oil
Rec
over
y F
acto
r (%
OO
IP)
PV Injection
B18-Cycle-1 CO2 Saturated Oil
B14-Cycle-1 Reference Curve
High Salinity
Low Salinity
High Rate
4
5
6
7
8
9
0 2 4 6 8 10 12 14
Brine PV Injected
pH
B18-Cycle-1 CO2 Saturated Oi
B14-Cycle-1 Reference Test
High Salinity
Low Salinity
HCO3- + OH- ↔ CO3
2- + H20
Is EOR by LowSal flooding a LowSal effect? Core No.
Swi %
TAging ° C
TFlooding ° C
Oil Low Salinity
Brine Formation Brine
B01 20.0 60 40 TOTAL Oil Low Salinity-7
NaCl 40000
ppm
Pure CaCl2 25000 ppm
B14 19.4 60 40 TOTAL Oil
Low Salinity-1
NaCl 1000
ppm
TOTAL FW
60
Low Salinity
10
0
10
20
30
40
50
0 2 4 6 8 10 12 14
Brine PV Injection
Oil
Rec
over
y F
acto
r (%
OO
IP)
B01-Cycle-1B14-Cycle-1 Reference Test
High Salinity
Low Salinity
High Rate
4
5
6
7
8
9
0 2 4 6 8 10 12 14
Brine PV Injected
pH
B01-Cycle-1
B14-Cycle-1 Reference Test
High Salinity
Low Salinity
Gradient in the concentration of the most active ions, Ca2+, most important.
Ca2+ + OH- ↔ [Ca--OH]+
Conclusion
• The chemical mechanism for wettability modification in sandstones and carbonates is different.
• NPD:• NPD:– 1% increase in oil recovery (OOIP) will give net
100-150 billion NOK
• Arild Nystad (former resource dir. at NPD)– IOR programs can give 3000 new billions NOK
Ongoing projects
• Carbonates– BP: limestone in Abu Dhabi– Maersk / UiS: limestone in Qatar– Total/NFR: Outcrop limestone– Total/NFR: Outcrop limestone– Saudi Aramco: limestone
• Sandstone:– Talisman/Total: low salinity
Personnel: EOR-Group