表面活性剂改变油藏润湿性提高采收率的机理

Mechanistic Study on Wettability Alteration of Reserviors and Its EOR Induced by Surfactants

我国现阶段采用常规一次、二次采油工艺后,采收率仍然相对较低,大量原油残留于油层孔隙中,表面活性剂在后续三次采油中起到重要作用。分别采用油湿性岩心和水湿性岩心,对比分析了水驱过程中表面活性剂改变润湿性从而对采收率的影响。采用非稳态法测定油水相渗曲线,确定了油水两相在岩石孔道中的分布规律。通过表面张力、接触角、毛细管力及附着功的测定研究了岩心驱替实验过程中表面活性剂改变固体表面润湿性提高水驱采收率的机理。结果表明:在不同润湿性的储层中,弱水湿性储层具有最高的水驱采收率。经体系(0.06%DTAB)驱替后,岩心表面润湿性转变为中性润湿性,相渗曲线上两相共渗区面积增大,Sor降低,同一含水饱和度下对应的油流动性更强。对于亲水岩石,水滴通常位于孔隙和岩石内壁,对油相的流动不产生显著影响。而在亲油岩石中,水呈珠滴状分布于岩石孔道中央,对油流影响显著。对不同体系下附着功的测定发现,随着水湿性的增强,体系的附着功不断减小,经体系(0.15%TX-100)驱替后的岩心表面水湿性最强,其对应的附着功最小。对不同体系下毛管力的测定发现,体系AES-1的水湿性最强,其对应的毛管力最大,此时毛管内油面位于毛管外水面之上,毛管力为驱油动力。

At present, there has been a relatively low recovery after the application of conventional primary recovery and secondary recovery processes in China, and a large proportion of crude oil remains in the pores of the reservoirs,surfactants play an important role in subsequent tertiary oil recovery. In this paper, oil-wet cores and water-wet cores were used to compare and analyze the influence of surfactant-induced wettability alteration on waterflooding recovery.The unsteady-state method was used to measure the relative permeability curve and determine the distribution regularities of oil-water two-phases in rock pores. Surface tension, contact angle, capillary force and adhesion work were measured to study the mechanism of wettability alteration of solid surface and its EOR induced by surfactants during core-flood experiment. The results indicated that among the reservoirs with different wettabilities, the reservoirs with weak water wettability had the highest water flooding recovery. After the system(0.06% DTAB)flooding, the wettability of the core surface turned into neutral wettability, the oil-water simultaneous vadose region area in the relative permeability curve increased, the residual oil saturation decreased, and the corresponding oil fluidity was the strongest under the same water saturation. For hydrophilic rocks, water droplets were usually located in the pores and the internal surface of the rocks, which had no significant effect on oil flow. But in oil-wet rocks,water was distributed in the center of pores in the form of droplet, which had a remarkable effect on oil flow. By measuring the adhesion work of different systems, the results indicated that the adhesion work decreased with the increasing of water wettability, the wettability of the system TX-100 was the strongest and the corresponding adhesion work was the lowest. Вy measuring the capillary force of different systems, the results indicated that the system AES-1had the strongest wettability alteration ability, and the corresponding capillary force was the largest. The oil level in the capillary was above the water level outside the capillary, and the capillary force had promoted oil displacement.