稠油油藏化学驱采收率的影响因素

Influence factor on oil recovery efficiency for chemical flooding of heavy oil reservoir

采用烷基聚氧丙烯醚硫酸盐和羧基甜菜碱两类两性表面活性剂与碱复配构建具有不同界面张力特点的驱油体系,通过驱油试验评价不同体系对桩西稠油采收率的影响,采用微观驱替试验研究不同体系提高采收率的机制。结果表明:界面张力与采收率没有明显的对应关系;碱通过维持油、水、固三相接触点亲油性和降低油水界面张力,减弱驱替介质沿油与岩石之间的渗入,增强驱替介质从原油中心的突进和分散,提高驱替压力和波及体积;相比于碱和原油反应产生的表面活性剂,外加的表面活性剂亲水性较强,会增强固体表面的亲水性,导致驱油剂沿孔隙壁面突进;表面活性剂-碱体系与原油形成的细分散水包油型乳状液加剧了驱油剂的窜进,不利于提高波及系数;对于稠油油藏,化学驱体系的波及系数是提高采收率的关键因素。

The systems with different interfacial tension（IFT） were built using the amphoteric surfactant polyoxypropylene alkyl ether sulfate and carboxyl betaine and base synthesized.The effects of different systems on the heavy oil recovery in Zhuangxi Oilfield were evaluated using oil displacement experiments.Then the displacement mechanism for different systems were studied by micro-displacement test.The results show the oil recovery has no corresponding relationship with the IFT.The alkali could keep the oil-water-solid contact point oil-wet and reduce the oil-water IFT to prevent the water from penetrating between the oil and solid.It makes the displacing agent flow through the oil,and enhances the displacement pressure and swept volume.Compared to the surfactant produced by the reaction of crude oil and alkali,the surfactant with stronger hydrophilic could enhance the water-wet ability of the solid surface which makes the displacing agent penetrate on the solid.The finely dispersed oil in water emulsion formed by the surfactant/alkali system mixed with oil aggravates the inroads of the displacing agent and decreases the sweep efficiency.Improving the sweep efficiency of the chemical drive system is a key factor in enhanced oil recovery for heavy oil reservoirs.