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

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). Outline. Introduction Associative polymers chemistry Adsorption in porous media

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

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

  2. Outline • Introduction • Associative polymers chemistry • Adsorption in porous media • Conclusion • Additional results IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  3. Polymer flooding: aqueous polymer solutions aqueous phase viscosity  reduction of mobility ratio R = (kw/hw)/(koil/hoil)  areal sweep efficiency improvement  vertical sweep efficiency improvement  (k2 > k3 > k1) • Well treatments: aqueous polymeric gels or microgels selective permeability reduction controlled adsorption   kW producing wells: water shutoff  injecting wells: profile/conformance control Introduction 1/3Polymers in IOR/EOR : polymer flooding and well treatments minimum adsorption is required IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  4. polymers with hydrophilic backbone bearing hydrophobic groups along the chains, capable of creating physical links between each other (Hydrophobically) Associative Polymers = • "Super" thickeners viscosity (Pa.s) a) Higher viscosities above cac b) Mechanical stability associative 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) non- associative c) Salt tolerance concentration (g/mL)  salinity   hydrophobic bonds   viscosity (≠standard polyacrylamides)  less polymer needed to achieve a given viscosity  high permeability reductions (well treatments) • Strong adsorption on surfaces associative polymers likely adsorb as multilayers Introduction 2/3Advantages of (hydrophobically) associative polymers for IOR/EOR IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  5. Associative polymers static adsorption • Volpert et al. -- Langmuir, 14, 1870-1879 (1998) • Li -- Oilfield Chemistry, Vol. 23, No. 4, 349-351 (2006) • 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 for well treatments • Eoff, Dalrymple & Reddy (2000's)  Halliburton's "Waterweb" process Introduction 3/3Associative polymers for IOR/EOR: literature review • Injectivity? Adsorption? • What makes a associative polymer more suitable for polymer flooding or well treatment operations ? IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  6. Outline • Introduction • Associative polymers chemistry • Adsorption in porous media • Conclusion • Additional results IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  7. 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) AP +equivalent non-AP • Polymers type 2: polyacrylic acids with alkyl hydrophobic groups ; (post-modification) AP +equivalent non-AP Associative polymers chemistry IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  8. Outline • Introduction • Associative polymers chemistry • Adsorption in porous media • Conclusion • Additional results IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  9. SiC (silicon carbide) sharp-edged grains, 50µm in size • k = 1000±50 10-15 m² ; j = 40±1% • hydrodynamic pore throats diameter dh≈ 10 µm Adsorption in porous media 1/6Experimental set-up (cont'd) & experimental procedure • Model granular packs • Polymer solutions • adsorption study injection of diluted polymer solutions • all solutions filtered on 3 µm calibrated membranes prior to injection • Experimental procedure • 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 eh : IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  10. Adsorption in porous media 2/6Polymers type 1: mobility reduction with equivalent non-AP Polymer solution injected: C = 0.84 g/L hr = 4.3 ; h = 3.5 cP • close to piston-like in-depth propagation • stabilized mobility reduction IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  11. Adsorption in porous media 3/6Polymers type 1: mobility reduction with AP Polymer solution injected : C = 0.45 g/L hr = 2.6 ; h = 2.1 cP • entry-face & internal plugging trend (?)  strong polymer adsorption IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  12. Adsorption in porous media 4/6Polymers type 1: adsorbed layers thicknesses estimations internal section 2-5 cm only AP • eh depends on the amount of polymer solution injected • eh ≈ 1.4-1.5 µm after only 1.3 PV injected  likely multilayer adsorption equivalent non-AP • eh does not depend on the amount of polymer solution injected • eh≈ 0.2 µm ~ single-chain size in solution IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  13. Adsorption in porous media 5/6Polymers type 2: mobility reductions with equivalent non-AP and AP internal section 2-5 cm only Polymer solutions injected : • equivalent non-AP (20g/L NaCl): • C = 1.5 g/L ; hr = 2.0 • AP 20 g/L NaCl: • C = 1.6 g/L ; hr = 2.2 • AP 58.4 g/L NaCl: • C = 3.2 g/L ; hr = 4.1 same volume fraction j = 0.3 • good in-depth propagation of both equivalent non-AP and AP IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  14. Adsorption in porous media 6/6Polymers type 2: adsorbed layer thicknesses estimation 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 IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  15. Outline • Introduction • Associative polymers chemistry • Adsorption in porous media • Conclusion • Additional results IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  16. Conclusion • 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 IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

  17. Outline • Introduction • Associative polymers chemistry • Adsorption in porous media • Conclusion • Additional results IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia 17

  18. Adsorption in porous media: additional results 1/3Polymers type 1 (micellar copolymerization): impact of molecular structure vs. salt concentration vs. polymer concentration • 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) Thickening ability IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia 18

  19. Adsorption in porous media: additional results 2/3Polymers type 1: long-term injections (0.5 mol-% C12) Pressure taps layout • Coreflood experiments: • SiC granular packs (50 µm grains) ; k = 1D ; f = 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 ; jeffective = 0.2 ; hrbulk = 1.7 1-5 cm • flow 3 Injected PV 130 Injected PV 0-1 cm 5-9 cm • viscous front propagation + polymer adsorption (Rm > hrbulk) • breakthrough, with C/C0 = 1 • entry-face plugging trend ? • "secondary adsorption" front propagation • entry + internal stabilization trends (?) • stable effluent concentration  origin of the secondary adsorption ? IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia 19

  20. 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 front reaches 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 IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia 20

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