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IEA Collaborative Project on EOR – 30th Annual Workshop and Symposium – 21-23 September 2009, Canberra, Australia

Associative Polymers for EOR: towards a better understanding

and control of their adsorption in porous media

D. Rousseau, R. Tabary, Z. Xu, G. Dupuis (IFP)S. Paillet, B. Grassl, J. Desbrières (EPCP/IPREM)

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia2

Outline

Introduction

Associative polymers chemistry

Adsorption in porous media

Conclusion

Additional results

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia3

Introduction 1/3Polymers in IOR/EOR : polymer flooding and well treatments

Polymer flooding: aqueous polymer solutions aqueous phase viscosity reduction of mobility ratio R = (kw/w)/(koil/oil)

areal sweep efficiency improvement

vertical sweep efficiency improvement

(k2 > k3

> k1)minimum adsorption is required

Well treatments: aqueous polymeric gels or microgels

producing wells: water shutoff

injecting wells: profile/conformance control

kW

controlled adsorptionselective permeability reduction

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia4

Introduction 2/3Advantages of (hydrophobically) associative polymers for IOR/EOR

(Hydrophobically) Associative Polymers

polymers with hydrophilic backbone bearing hydrophobic groups along the chains, capable of creating physical links between each other

=

Strong adsorption on surfaces

associative polymers likely adsorb as multilayers

high permeability reductions (well treatments)

b) Mechanical stability

high viscosities with short chains (e.g. 1.106 g/mol)(≠ standard polyacrylamides: 18.106 g/mol)

less sensitivity to shear degradation (surface facilities + near wellbores)

"Super" thickeners

visc

osi

ty (

Pa.

s)

concentration (g/mL)

non- associative

associative

a) Higher viscosities above cac

less polymer needed to achieve a given viscosity

c) Salt tolerance

salinity hydrophobic bonds viscosity(≠standard polyacrylamides)

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia5

Introduction 3/3Associative polymers for IOR/EOR: literature review

Associative polymers flooding suggested in the 1980's

patents: Evani et al. (1984), Landoll (1985), Bock et al. (1987), Ball et al. (1987)

review by Taylor & Nasr-el-Din (1998, updated 2007 – Can. Int. Petr. Conf. paper 2007-016)

renewed interest in the 2000's CNOOC's offshore polymer flooding pilot in Bohai bay: Zhou et al. (IPTC 11635 - 2007, paper B7 - 2008 IEA/EOR, Beijing)

Associative polymers static adsorption

Li -- Oilfield Chemistry, Vol. 23, No. 4, 349-351 (2006)

Volpert et al. -- Langmuir, 14, 1870-1879 (1998)

Associative polymers for well treatments Eoff, Dalrymple & Reddy (2000's) Halliburton's "Waterweb" process

Injectivity? Adsorption? What makes a associative polymer more suitable

for polymer flooding or well treatment operations ?

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia6

Outline

Introduction

Associative polymers chemistry

Adsorption in porous media

Conclusion

Additional results

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia7

Associative polymers chemistry

Synthesis methods Post-modification = grafting hydrophobic groups on a pre-existing hydrophilic backbone

Micellar copolymerization = simultaneous polymerization in aqueous solutions of the hydrophilic monomers and of the hydrophobic monomers, solubilized in micelles

Present study Polymers type 1: sulfonated polyacrylamides with alkyl hydrophobic groups; (micellar copolymerization)

Polymers type 2: polyacrylic acids with alkyl hydrophobic groups ; (post-modification)

AP + equivalent non-AP

AP + equivalent non-AP

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia8

Outline

Introduction

Associative polymers chemistry

Adsorption in porous media

Conclusion

Additional results

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia9

Adsorption in porous media 1/6Experimental set-up (cont'd) & experimental procedure

Model granular packs SiC (silicon carbide) sharp-edged grains, 50µm in size k = 1000±50 10-15 m² ; = 40±1% hydrodynamic pore throats diameter

dh ≈ 10 µm/8215.115.1 kdd ch

Polymer solutions

Experimental procedure

adsorption study injection of diluted polymer solutions all solutions filtered on 3 µm calibrated membranes prior to injection

adsorption study monophasic flow conditions polymer solution injection mobility reduction (Rm) i.e. resistance factor (RF) brine injection permeability reduction (Rk) i.e. residual resistance factor (RRF)

estimation of hydrodynamic adsorbed layers thicknesses h :

)1()2/( 4/1 Rkdhh

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia10

Adsorption in porous media 2/6Polymers type 1: mobility reduction with equivalent non-AP

Polymer solution injected:

C = 0.84 g/L

r = 4.3 ; = 3.5 cP

0

1

2

3

4

5

6

7

8

9

10

0 0.5 1 1.5

# Pore volumes injected

Rm

= D

P(p

oly

mer

) / D

P(b

rin

e)

2-5 cm0-2 cm

5-10 cm

flow direction

close to piston-like in-depth propagation stabilized mobility reduction

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia11

Adsorption in porous media 3/6Polymers type 1: mobility reduction with AP

0

1

2

3

4

5

6

7

8

9

10

0 0.5 1 1.5

# Pore volumes injected

Rm

= D

P(p

oly

mer

) / D

P(b

rin

e)

2-5 cm

flow direction

0-2 cm

5-10 cm

Polymer solution injected :

C = 0.45 g/L

r = 2.6 ; = 2.1 cP

entry-face & internal plugging trend (?) strong polymer adsorption

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia12

Adsorption in porous media 4/6Polymers type 1: adsorbed layers thicknesses estimations

0.0

0.5

1.0

1.5

2.0

10 100Wall shear rate, g• (s-1)

Ad

sorb

ed l

ayer

th

ickn

ess,

h

(µm

)

Associative polymers

Equivalent non-associative polymers

equivalent non-APh does not depend on the amount of

polymer solution injectedh ≈ 0.2 µm ~ single-chain size in solution

APh depends on the amount of polymer

solution injectedh ≈ 1.4-1.5 µm after only 1.3 PV injected

likely multilayer adsorption

internal section 2-5 cm only

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia13

Adsorption in porous media 5/6Polymers type 2: mobility reductions with equivalent non-AP and AP

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4

# Pore volumes injected

Rm

= D

P(p

oly

mer

) / D

P(b

rin

e)

Associating polymers

Equivalent non-associating polymers - 20 g/L NaCl

20 g/L NaCl 58.4 g/L NaCl

flow direction

2-5 cm section only Polymer solutions injected :

equivalent non-AP (20g/L NaCl):

C = 1.5 g/L ; r = 2.0

AP 20 g/L NaCl:

C = 1.6 g/L ; r = 2.2

AP 58.4 g/L NaCl:

C = 3.2 g/L ; r = 4.1

internal section 2-5 cm only

same volume fraction = 0.3

good in-depth propagation of both equivalent non-AP and AP

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia14

Adsorption in porous media 6/6Polymers type 2: adsorbed layer thicknesses estimation

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0 1 2 3 4 5# Experimental phase

Ad

sorb

ed l

ayer

th

ickn

ess,

h

(µ

m)

Associative polymersEquivalent non-associative polymers

20 g/L NaCl

Porous medium #1

Porous medium #2

injection 1: polymers20 g/L NaCl

injection 2: brine58.4 g/L NaCl

injection 3: polymers58.4 g/L NaCl

internal section 2-5 cm only

AP adsorbed layer collapse when exposed to higher salinity brine over-adsorption occurs when AP are injected in higher salinity brine

likely salinity-controlled multilayer adsorption

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia15

Outline

Introduction

Associative polymers chemistry

Adsorption in porous media

Conclusion

Additional results

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia16

Adsorption behavior in porous media of 2 types of associative polymers (AP) has been investigated

adsorption appears as a key parameter governing AP propagation in porous media

adsorption is a key parameter to address for EOR AP applications

A control of the adsorption is and must be possible (hydrophobic bonds = low-energy bonds)

control through salinity is possible

control through shear-rate ?

Ongoing work on this topic @ IFP

various injections conditions

various polymer chemistries

modeling AP adsorption in porous media

Conclusion

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia17

Outline

Introduction

Associative polymers chemistry

Adsorption in porous media

Conclusion

Additional results

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia18

Adsorption in porous media: additional results 1/3Polymers type 1 (micellar copolymerization): impact of molecular structure

Set of associative sulfonated polyacrylamides (G. Dupuis work) same backbones: 20 mol-% AMPS ; Mw = 106 g/mol C8, C12 and C18 hydrophobic side groups 0.1, 0.2 and 0.5 mol-% hydrophobic monomers (+ equivalent non-associative polymers)

vs. polymer concentration vs. salt concentration

Thickening ability

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia19

Adsorption in porous media: additional results 2/3Polymers type 1: long-term injections (0.5 mol-% C12)

Coreflood experiments: SiC granular packs (50 µm grains) ; k = 1D ; = 0.4 ; PV ≈ 8 cm3 low flow rate: Q = 2 cc/h (vD ≈ 1 foot/day) ; gwall = 15 s-1

diluted polymer solution: C = 0.9 g/L ; effective = 0.2 ; rbulk = 1.7

•

Pressure taps layout

flowflow

1-5 cm

5-9 cm0-1 cm

viscous front propagation + polymer adsorption (Rm > r

bulk)

breakthrough, with C/C0 = 1 entry-face plugging trend ?

3 Injected PV

"secondary adsorption" front propagation entry + internal stabilization trends (?) stable effluent concentration origin of the secondary adsorption ?

130 Injected PV

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IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia20

Adsorption in porous media: additional results 3/3Polymers type 1: re-injection test (0.5 mol-% C18)

Assumption: 2 components in the polymer solutions (chemical structure heterogeneity?) vast majority of low-adsorption (weakly damaging) polymers

quick effluent breakthrough, C/C0=1 minority of strong-adsorption (strongly damaging) polymers

slow propagation of the "secondary front"

Experimental testing: effluent collection until the secondary frontreaches half of the core

"cleaned" solution effluent re-injection in a fresh core

Practical outcomes for polymer flooding with associative polymers:

towards specific in-depth filtration procedures? improvement in chemical synthesis methods? controlling the injectivity of associative polymers seems possible