低界面张力下乳化程度对二元驱采收率的影响

Effect of Emulsifying Degree on Oil Recovery of Surfactant-polymer Compound Flooding with Low Interfacial Tension

为研究砾岩油藏乳化程度与二元复合驱采收率的关系,通过乳化(调节表面活性剂的加量)调控驱油体系乳化强度以及乳化体系在长岩心中的运移规律,研究了不同乳化强度的部分水解聚丙烯酰胺/环烷基石油磺酸盐表面活性剂(KPS)二元体系的驱油效果,明确了乳化程度对提高采收率的作用。结果表明,油水界面张力为5×10^(-2)mN/m的中等乳化二元体系的驱油效率比5×10^(-3)mN/m无乳化体系的高8%。当二元体系达到临界黏度后,油水界面张力为5×10^(-2) mN/m数量级、乳化综合指数适宜的乳状液对驱油体系黏度具有补偿作用,能够长距离保持驱油体系黏度的稳定性,有利于进一步提高采收率。砾岩油藏二元复合驱多因素耦合提高采收率决策中,在渗透率极差较大时通过调节驱油体系黏度比和乳化综合指数可实现提高采收率;渗透率级差≤6时,通过界面张力和乳化综合指数调控实现大幅度提高采收率。当剩余油饱和度小于50%时,乳化综合指数控制在50%~70%;剩余油饱和度大于50%时,乳化综合指数控制在30%~50%。在新疆某区块实施"低界面张力和可控乳化"二元复合驱技术,采收率提高28%,含水率降幅大于40%,实现了驱油体系"梯次降黏、逐级动用"的个性化设计。图11表3参17。

In order to research the relationship between emulsifying and oil recovery of surfactant-polymer(SP)compound flooding for the conglomerate reservoir,by controlling the emulsifying intensity and the migration law of emulsifying system in long core,the oil displacement effect of binary compound system of partially hydrolyzed polyacrylamide(HPAM)and naphthenic sulfonate surfactant(KPS)with different emulsification intensity was studied,the effect of emulsifying degree on EOR was clarified.The experiment results showed that the medium emulsified SP system with oil-water interfacial tension(IFT)of 5×10-2 mN/m had 8%oil displacement efficiency more than the non-emulsified SP system with IFT of 5×10-3 mN/m.When the critical viscosity of SP system reached,the emulsion with IFT of 5×10-2 mN/m and suitable emulsion composite index could compensate the viscosity of oil displacement system and keep the stability of the viscosity of oil displacement system for a long distance,which was beneficial to EOR.In the multi-factor coupling of EOR decision system for conglomerate reservoir in SP compound flooding,the oil recovery could be increased by adjusting the viscosity ratio of flooding system and emulsion composite index when the permeability range was large.When the permeability ratio was less than or equal to 6,the oil recovery could be greatly improved by controlling the IFT and emulsion composite index.When the remaining oil saturation was less than 50%,the emulsion composite index was controlled at 50%—70%.While the former was more than 50%,the latter was controlled at 30%—50%.The SP compound flooding technology with low IFT and controllable emulsification was implemented in Xinjiang oilfield,the oil recovery rate increased by 28%and the reduction of water content decreased by more than 40%,which realized the personalized design of step-by-step viscosity reduction and step-by-step mobilization of oil displacement system.