zeta potential changes at mineral- brine and oil-brine interfaces ... 10.… · zeta potential...

Zeta potential changes at mineral-brine and oil-brine interfaces control improved oil recovery during ‘smart’ waterflooding

Matthew JacksonDawoud Al-Mahrouqi, Shuai LiDepartment of Earth Science and Engineering, Imperial College London

Low salinity (‘smart’) waterflooding successesIn sandstones………

Example from RezaeiDoust et al. (2011) reproduced in Jackson et al., Fuel, (2016)

© Imperial College London

Low salinity (‘smart’) waterflooding successes

(Yousef et al., 2010)

In carbonates………


All looking rosy……but……

Example from Nasralla and Nasr-El-Din (2014) reproduced in Jackson et al., Fuel, (2016)


All looking rosy……and……


0

10

20

30

40

50

60

0 3 6 9 12 15

FMB 100dFMB

Cum

ulat

ive o

il re

cove

ry %

PVs injected

0% incremental

(Austad et al., 2011)

‘Smart’ waterflooding: what we don’t know

• Why it doesn’t always work and/or is not always repeatable

• How to identify candidate reservoirs without conducting numerous costly core-flooding experiments

• How to predict the optimum modified (controlled) injection brine composition

Jackson et al., Fuel, (2016)


Why zeta potential?Measure of electrical charge at an interface (mineral-brine, oil-brine, gas-brine etc…..)

Controls the electrostatic interactions between mineral surfaces and polar species in aqueous and non-aqueous solution

Probes mineral surface so sensitive to wetting state

Mechanisms invoked to explain improved recovery during smart waterflooding cause changes in zeta potential at mineral-brine interface

• Concentration of ‘potential determining ions’ (PDIs)• Ion exchange on mineral surfaces• Double layer expansion

Jackson et al., Fuel, (2016)© Imperial College London

Zeta potential at mineral-brine interfaces

Glover and Jackson (2010)


Sandstones and potential determining ions (PDIs)


• Zeta potential depends on pH for metal oxides (protonation and deprotonation reactions at mineral surface)

• Zeta potential also depends on adsorption of salt species onto mineral surfaces (e.g. Ca2+, Mg2+)

• ‘Indifferent’ ions do not directly interact with surface

Ishido and Mizutani, 1981

Zeta potential and double layer expansion


• Generally assumed zeta potential at mineral-brine interfaces increases in magnitude during dilution

• Zeta potential also depends on adsorption of salt species onto mineral surfaces (e.g. Ca2+, Mg2+)

Example from Vinogradov et al. (2010) reproduced in Jackson et al., Fuel, (2016)

Carbonates and potential determining ions (PDIs)


• Zeta potential depends on pH in unbuffered experiments (pCa allowed to vary)

• Zeta potential constant in buffered experiments (pCafixed)

• Proton is not a PDI for the carbonate mineral surface

Foxall et al., 1979


-20

-15

-10

-5

0

5

0 0,5 1 1,5 2 2,5 3 3,5

Zeta

pot

entia

l (m

V)

pPDI

Ca Mg SO4

FMB SW

• Identical behavior of Ca and Mg within experimental error• Sensitivity to SO4 much lower (not a PDI?) AlRoudhan et al., Col. Surf. A, 2016


-14

-12

-10

-8

-6

-4

-2

0

2

4

0 0,5 1 1,5 2 2,5 3 3,5

Zeta

pot

entia

l (m

V)

pCa

0.05M

2M

0.5M

• Sensitivity to pCa and pMg decreases with increasing total ionic strength

AlRoudhan et al., Col. Surf. A, 2016

Increasing ionic strength

Similar to 10x dilute seawater

Similar to typical formation brine


0 0.5 1 1.5 2 2.5 3 3.5-12

-10

-8

-6

-4

-2

0

2

4

6

8Ze

ta P

oten

tial (

mV)

pCa

NaCl = 0.5 M

NaCl = 2 M

NaCl-EQ experiments

Estaillades

Ketton

Portland

• Different carbonates exhibit different behaviourAlMahrouqi et al., Adv. Col. Int. Sci., 2017

Ketton and Portland

Estaillades

Measurement of zeta potential: The zetameter

Example from Malvern

• Measurement of zeta potential is routine in materials science

• Off-the-shelf commercial equipment available

BUT….• Require powdered samples• Limited range of

pressure/temperature/ionic strength

• Only one fluid phase present

IN NATURE……• Intact rocks• High P/T/I• Oil + water


Experimental setup

O

BB

O

Pump

Oil reservoir

Core holder

NI Data Acquisition

System

M

P1 P2

Manometer

Confining pressure

pump

Pressure transducer

SamplingSampling

V1

V2

V3V4

V5V6

Thermocouple

Metering valve

Oven

Coiled flowline

Vinogradov et al., 2010FP

VCrww

w

j σµςε

=∂∂

==0

Typical experimental results

AlRoudhan et al., Zeta Potential of Intact Natural Limestone: Impact of Potential-Determining Ions, Col Surf A 2016

-0,99

-0,94

-0,89

-0,84

-0,79

-800

-600

-400

-200

0

200

400

600

0 1000 2000 3000 4000 5000 6000

Volta

ge, m

V

Pres

sure

, kPa

Time, s

Synthetic Formation Brine (2M, c. 250,000ppm)

-30

-25

-20

-15

-10

-5

0

5

10

Zeta

pot

entia

l (m

V)

Sst Carbonates

FMB to dilute seawater

Zeta potential in brine-saturated (water-wet) carbonates and sandstones

Link between zeta potential and wettability

Increasing oil wetnessModified from Jackson et al., Sci. Rep. (2016)

-7

-5

-3

-1

1

3

5

7

9

00,20,40,60,81

Cha

nge

in z

eta

pote

ntia

l afte

r agi

ng (m

V)

Amott Water Wetting Index (-)



-7

-5

-3

-1

1

3

5

7

9

00,20,40,60,81

Cha

nge

in z

eta

pote

ntia

l afte

r agi

ng (m

V)


+++

++++

+++

+

+

++++

+

+

+

+++

Water wet

Water wet

+ ++ +++ ++ ++ +++

Water wet

+



-7

-5

-3

-1

1

3

5

7

9

00,20,40,60,81

Cha

nge

in z

eta

pote

ntia

l afte

r agi

ng (m

V)


Water

Oil wet

Oil wetOil wet

Water wet

Water wet Water wet

Oil

---

-

- - - -- - -- --- -+++++

-- - - - - - -

---

++

+



-7

-5

-3

-1

1

3

5

7

9

00,20,40,60,81

Cha

nge

in z

eta

pote

ntia

l afte

r agi

ng (m

V)


Trend indicates negative zeta potential at oil-brine interface



-7

-5

-3

-1

1

3

5

7

9

00,20,40,60,81

Cha

nge

in z

eta

pote

ntia

l afte

r agi

ng (m

V)


Water

Oil wet

Oil wetOil wet

Water wet

Water wet Water wet

Oil

+

+ +++++++++++++++ +

+

++++ + +

++++++

++++

++++++




-7

-5

-3

-1

1

3

5

7

9

00,20,40,60,81

Cha

nge

in z

eta

pote

ntia

l afte

r agi

ng (m

V)



Trend indicates positive zeta potential at oil-brine interface



-7

-5

-3

-1

1

3

5

7

9

00,20,40,60,81

Cha

nge

in z

eta

pote

ntia

l afte

r agi

ng (m

V)



Trend indicates positive zeta potential at oil-brine interface

Sandstone

Link between zeta potential and EOR in carbonates: Conventional LSW with –ve oil

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35

SPM

1

ζ F

SPM

2

ζ i(sw

)

SPM

3

ζ i(20

dsw)

Cumulative incremental oil recovery

FMB SW 20dSWCum

ulat

ive

oil r

ecov

ery

(%)

Pore volume injected, ml

Oil D

Jackson et al., Zeta potential in oil-water-carbonate systems and its impact on oil recovery during CSW, Scientific Reports 2016

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35

SP

M1

ζ F

SP

M2

ζ i(sw

)

SP

M3

ζ i(20

dsw)

FMB SW 20dSWCum

ulat

ive

oil r

ecov

ery

(%)


Link between zeta potential and EOR in carbonates: Conventional LSW with +ve oil

Oil A

Jackson et al., Zeta potential in oil-water-carbonate systems and its impact on oil recovery during CSW, Scientific Reports 2016

Link between zeta potential and EOR in carbonates: Inverted LSW with +ve oil

Improved recovery with oil A by increasing salinity!Change in zeta potential is key, not change in salinity

0102030405060708090

100

0 5 10 15 20 25 30 35

SPM

1

ζ F

SPM

2

ζ i(sw

)

SPM

3

ζ i(FM

B)Cumulative

incremental oil recovery

20dSW SW FMBCum

ulat

ive

oil r

ecov

ery

(%)


Jackson et al., 2016

Link between zeta potential and EOR in sandstones

0

10

20

30

40

50

0

10

20

30

40

50

60

70

0 20 40 60 80

Pres

sure

diff

eren

ce (p

si)

&pH

Oil

Rec

over

y, %

OO

IP

Pore Volume

Oil D

SW30dFMB2

0

5

10

15

20

25

0

10

20

30

40

50

60

70

0 5 10 15 20 25

Pres

sure

diff

eren

ce (p

si)

&pH

Oil

Rec

over

y, %

OO

IP

Pore Volume

Oil A

SW30d FMB2

Incremental oil recovery during conventional CSW with –ve oil is around 5.25% OOIP

Incremental oil recovery during inverted CSW with +ve oil is around 3.25% OOIP

Correlation between IOR and change in zeta potential – all experiments

Normalize the change in zeta potential resulting from CSW by the change in zeta potential corresponding to wettability alteration

Jackson et al., Sci. Rep. (2016)

FMBSorSw

FMBSw

CSWSw

FMBSw

n−==

==

−−

=11

11

ζζζζζ

0

2

4

6

8

10

12

14

0 2 4 6 8 10 12 14 16

IOR

(%)

Zeta potential of oil droplets

Hexadecane droplets in 0.4 mM NaClO4Suggested that hydroxide ions charge and stabilize dropletsBut emulsions become unstable > 5mM salt (how measure zeta potential?)(from Beattie and Djerdev, 2004)

Zeta potential and CSWIf the oil-water interface has a negative zeta potential:• IOR observed by CSW to produce a more negative zeta

potential on mineral surfaces • conventional approach of diluting formation brine and/or

seawater is successfulIf the oil-water interface has a positive zeta potential:• IOR observed by CSW to produce a more positive zeta

potential on mineral surfaces • increasing the concentration of Ca or Mg ions may be

successful in carbonates

Studies that have failed to observe improved recovery using the conventional (dilution) approach to CSW may have been dealing with a positive zeta potential at the oil-water interface

zeta potential changes at mineral- brine and oil-brine interfaces ... 10.… · zeta potential...

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