Preparation of cationic polyacrylamide microsphere emulsion and its performance for permeability reduction

Pet.Sci. Preparation of cationic polyacrylamide microsphere emulsion and its performance for permeability reduction Guo Aijun 1 2 Geng Yiran 1 2 Zhao Lili 1 2 Li Jun 0 2 Liu Dong 1 2 Li Peng 1 2 0 Technical Department of Ethylene Complex, Petrochina Dushanzi Petrochemical Company , Karamayi, Xinjiang 833600 , China 1 State Key Laboratory of Heavy Oil Processing and College of Chemical Engineering, China University of Petroleum (East China) , Qingdao, Shandong 266580 , China 2 Morphology and stability of the crude product In this paper, cationic polyacrylamide microspheres (CPAM) were synthesized using acrylamide (AM) and methacryloyloxyethyl trimethyl ammonium chloride (TMAEMC) as monomers, ammonium sulfate as dispersant, poly(acryloyloxyethyl trimethyl ammonium chloride) (PAETAC) as dispersion stabilizer, and ammonium persulfate as initiator. The synthetic method was dispersion polymerization. The effects of monomer ratio (AM/TMAEMC), dispersant concentration, and dispersion stabilizer dosage on dispersion polymerization were systematically studied to determine the optimal preparation conditions. The structure and viscosity of the synthesized polymer were characterized by FTIR and capillary viscometry, respectively, and the particle sizes and distribution of the polymer tests were conducted to measure the permeability reduction performance of the microspheres at various concentrations in sand packs with different permeability. Results show that CPAM emulsion of a solids Dispersion polymerization; cationic polyacrylamide microspheres; profile modification; permeability reduction 1 Introduction During a secondary or enhanced oil recovery process, a substantial amount of oil may be bypassed by the injected Wang, 2003; Fletcher et al, 1992 ; Liu et al, 2006 ). In order to enhance oil recovery, the widely used method is injecting water cutoff materials to control formation permeability and then to divert the follow-up injected fluid into the unswept zones, without damaging oil productivity (Hou et al, 2011; Lu et al, 2012; Shi et al, 2010; 2012; Dong et al, 2010) . So it is necessary to synthesize a new water cutoff material to reduce water cut of produced fluids and improve oil-producing efficiency in formations (Fielding et al, 1994; Ning et al, 2007; Lin et al, 2008; 2009; Lu et al, 2010; Feng et al, 2010; Wang and Li, 2011; Qiao et al, 2012) . Polymer microspheres are newly developed water cutoff material. After hydration, swollen polymer microspheres progressively adsorb and deposit in pore throats to closure for such permeability control treatment: the dispersed polymer microsphere emulsion has relatively low viscosity; the polymer microsphere emulsion; and the most important is that the microspheres may be injected into formations continuously (Lei et al, 2011; Lin et al, 2003; 2011a; 2011b) . However, most polymer microspheres are nonionic, showing weak interaction with clay. In order to enhance the interaction between polymer microspheres with clay, this investigation tries to incorporate cationic monomer into polymers. Water dispersion polymerization is also a newly developed process for synthesizing polymer microspheres. This technology is simple in operation, and water is used, instead of organic solvent, to dissipate heat during reaction; hence, secondary pollution and environmental impact can be reduced. Therefore, research into water dispersion methods has important theoretical and practical values (Cho et al, 2002; Grazon et al, 2011; Semsarilar et al, 2012; Wang et al, 2011a; 2011b; 2011c; Liu et al, 2011; 2012; Ondaral et al, N,N’n H2C 2010; Song et al, 2003; Wu et al, 2008) . 2 Experimental 2.1 Experimental materials from the China National Medicines Corporation Ltd.; methacryloyloxyethyl trimethyl ammonium chloride were purchased from the Penglai Spark Chemical Co., Ltd. AM and TMAEMC were used as monomers, AS and sodium bicarbonate as dispersants, and MEDAM as a crosslinker. 2 . 2 P r e p a r a t i o n o f c a t i o n i c p o l y a c r y l a m i d e microspheres 2.2.1 Synthesis of a cationic dispersion stabilizer, poly(acryloyloxyethyl trimethyl ammonium chloride) (PAETAC) Two grams of AETAC was dissolved in 50 mL deionized was kept flowing through the flask for 45 min and then the temperature for 1-2 h under stirring. Afterwards the reaction time was extended for about 3 h at this temperature. Nitrogen m H2C O H C C NH2 + n (CH2 O CH2 CH2N CH3 Cl - ) CH3 C C O CH3 + CH3 2.3 IR characterization The copolymer after purification was dried to constant weight and pressed with KBr to disc form, and then a Fourier transform infrared spectrometer (NEXUS, Nicolet Co., USA) was used to characterize the cationic acrylamide polymer structure. 2.4 Determination of viscosity of the copolymer The apparent viscosity of the crude product was determined with a NDJ-1 rotary viscometer. The dried CPAM was dissolved in deionized water to prepare a CPAM the viscosity of (...truncated)