© IFP Controlled CO 2 | Diversified fuels | Fuel-efficient vehicles | Clean refining | Extended reserves IEA Collaborative Project on EOR – 30th Annual Workshop and Symposium – 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)

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

© IFP IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium September 2009, Canberra, Australia 3 Introduction 1/3 Polymers in IOR/EOR : polymer flooding and well treatments  Polymer flooding: aqueous polymer solutions  aqueous phase viscosity  reduction of mobility ratio R = (k w /  w )/(k oil /  oil )  areal sweep efficiency improvement   vertical sweep efficiency improvement (k 2 > k 3 > k 1 ) minimum adsorption is required  Well treatments: aqueous polymeric gels or microgels producing wells: water shutoff injecting wells: profile/conformance control   k W  controlled adsorption selective permeability reduction

© IFP IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium September 2009, Canberra, Australia 4 Introduction 2/3 Advantages 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 g/mol) (≠ standard polyacrylamides: g/mol)  less sensitivity to shear degradation (surface facilities + near wellbores)  "Super" thickeners viscosity (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)

© IFP IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium September 2009, Canberra, Australia 5 Introduction 3/3 Associative 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 )  renewed interest in the 2000's  CNOOC's offshore polymer flooding pilot in Bohai bay: Zhou et al. (IPTC , paper B IEA/EOR, Beijing)  Associative polymers static adsorption  Li -- Oilfield Chemistry, Vol. 23, No. 4, (2006)  Volpert et al. -- Langmuir, 14, (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 ?

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

© IFP IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium September 2009, Canberra, Australia 7 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

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

© IFP IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium September 2009, Canberra, Australia 9 Adsorption in porous media 1/6 Experimental set-up (cont'd) & experimental procedure  Model granular packs  SiC (silicon carbide) sharp-edged grains, 50µm in size  k = 1000± m² ;  = 40±1%  hydrodynamic pore throats diameter  d h ≈ 10 µm  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 :

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

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

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

© IFP IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium September 2009, Canberra, Australia 13 Adsorption in porous media 5/6 Polymers type 2: mobility reductions with equivalent non-AP and AP 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

© IFP IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium September 2009, Canberra, Australia 14 Adsorption in porous media 6/6 Polymers 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

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

© IFP IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium September 2009, Canberra, Australia 16  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 IFP  various injections conditions  various polymer chemistries  modeling AP adsorption in porous media Conclusion

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

© IFP IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium September 2009, Canberra, Australia 18 Adsorption in porous media: additional results 1/3 Polymers type 1 (micellar copolymerization): impact of molecular structure  Set of associative sulfonated polyacrylamides (G. Dupuis work)  same backbones: 20 mol-% AMPS ; Mw = 10 6 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

© IFP IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium September 2009, Canberra, Australia 19 Adsorption in porous media: additional results 2/3 Polymers type 1: long-term injections (0.5 mol-% C12)  Coreflood experiments:  SiC granular packs (50 µm grains) ; k = 1D ;  = 0.4 ; PV ≈ 8 cm 3  low flow rate: Q = 2 cc/h (v D ≈ 1 foot/day) ;  wall = 15 s -1  diluted polymer solution: C = 0.9 g/L ;  effective = 0.2 ;  r bulk = 1.7 Pressure taps layoutflow 1-5 cm 5-9 cm0-1 cm  viscous front propagation + polymer adsorption (Rm >  r bulk )  breakthrough, with C/C 0 = 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

© IFP IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium September 2009, Canberra, Australia 20 Adsorption in porous media: additional results 3/3 Polymers 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/C 0 =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