表面活性剂对水驱普通稠油油藏的乳化驱油机理

Oil Emulsion and Displacement Mechanism of Surfactants during Water Flooding in Common Heavy Oil Reservoir

为了研究乳化降黏驱油剂对不同渗透率的水驱普通稠油油藏的驱油效率和孔隙尺度增效机理,选取了烷基酚聚氧乙烯醚(J1)、α-烯基磺酸盐类表面活性剂(J2)、十二烷基羟磺基甜菜碱(J3)、J3与烷基酚聚氧乙烯醚羧酸盐复配表面活性剂(J4)作为驱油剂,开展了4种驱油剂一维驱油和微观驱油模拟实验,明确了乳化降黏驱油剂在孔隙尺度的致效机理。结果表明,降低界面张力对提高驱油效率的作用大于提高乳化降黏率。在油藏条件下,乳化降黏驱油剂需要依靠乳化降黏和降低界面张力的协同增效作用,才能大幅提高驱油效率。乳化降黏驱油剂的乳化能力越强、油水界面张力越低,驱油效率增幅越大。当化学剂乳化降黏率达到95%时,油水界面张力从10^(-1)mN/m每降低1个数量级,化学剂在高渗透和低渗透岩心中的驱油效率依次提高约10.0%和7.8%。乳化降黏驱油剂注入初期通过降低界面张力,使得高渗透岩心和低渗透岩心中的驱替压力分别为水驱注入压力的1/2和1/3,从而提高注入能力。注入后期大块的原油被乳化形成大量不同尺寸的油滴,增强原油流动性,提高驱油效率。乳化形成的界面相对稳定的稠油油滴,能暂堵岩石的喉道和大块稠油与岩石颗粒形成的通道。油滴的暂堵叠加效应,使高渗透和低渗透岩心的驱替压差分别为水驱压差的5.2倍和32.3倍,大幅提高了注入压力,从而扩大平面波及面积。降黏驱油剂驱油实现了提高驱油效率的同时扩大波及范围。研究结果为水驱稠油开发用驱油剂的研发提供参考,为大幅提高水驱普通稠油采收率奠定基础。

Alkylphenolpolyethoxylate(J1),α-alkenyl sulfonate surfactant(J2),dodecyl hydroxysulfobetaine(J3)and combinational surfactants(J4)were selected as oil displacing agents,in order to study the oil displacement efficiency and pore scale enhancement mechanism of emulsification viscosity reducing oil displacing agents in water flooding for common heavy oil reservoirs with different permeability.The simulation experiments of one-dimensional displacement and micro-displacement of 4 kinds of displacement agents were carried out.The mechanism of emulsifying viscosive-reducing oil displacement agent at pore scale was clarified.The results showed that reducing interfacial tension had more effect on improving oil displacement efficiency than increasing emulsification viscosity reduction.Emulsified viscosity reducing oil displacement agents relied on the synergistic effect of emulsified viscosity reducing and interfacial tension reduction,in order to significantly improve oil displacement efficiency in reservoir.The stronger the emulsification ability and lower the interfacial tension between oil and water of emulsified viscosity reducing oil displacement agents,the greater the increase in oil displacement efficiency was.When the viscosity reduction rate of chemical emulsification reached 95%,the interfacial tension between oil and water decreased by one order of magnitude from 10-1 mN/m,the oil displacement efficiency of chemical agents in high permeability and low permeability cores increased about 10.0%and 7.8%respectively.At the initial stage of oil displacement agent injection,the displacement pressure of high permeability and low permeability core was 1/2 and 1/3 of the water flooding pressure by reducing the interfacial tension respectively,so as to improve the injection capacity.At the later stage of injection,large blocks of crude oil were emulsified to form a large number of oil droplets with different sizes,which enhanced the fluidity of crude oil and improved the efficiency of oil displacement.The viscous oil droplets formed by emulsification with relatively stable interface could temporarily block the throat of rock and the channel formed by large heavy oil and rock particles.Through the temporary plugging superposition effect,the displacement pressure in high permeability and low permeability core was 5.2 times and 32.3 times as high as that of water flooding respectively,so the injection pressure was greatly increased and then the plane sweep area was expanded.Viscosity reducing oil displacing agent could improve oil displacement efficiency and expand the sweep range at the same time.The research results pointed out the direction of research and development of water flooding agent for heavy oil,and laid a foundation for greatly improving the recovery of water flooding for common heavy oil.