毛管力自吸采油

Oil by Capillary Spontaneous Imbibitions

水自进吸入裂缝性碳酸盐储层是一种价廉、重要的二次采油方法。但是在油润湿-中间润湿时由于毛管力为负值,水不可能自吸进入基质孔隙。在所有已探明的碳酸盐储层中约有80%为油润湿-中间润湿,所以必须寻求将油润湿变为水润湿方法。表面活性剂长期以来在石油开采中主要用来降低油水界面张力,用于调节润湿性的研究尚在探索和开发之中。前人的实验室研究表明,海水具有将碳酸盐岩调节至弱水润湿性的作用,有助于通过自吸提高采收率,温度较高时效果尤为明显。在高黏油注水时,一般认为毛管力可以忽略,对两种黏度高达11500mPa·s的重油研究结果表明,在水驱重油时毛管力仍起主要作用。在注水速度低时,水自吸有助于通过稳定水驱提高采收率。本文根据并联双孔隙模型和Poiseuille公式研究表明,在注水速度等于和小于某一临界值时不会滞留原油,与其他作者的某些结果不尽一致。

Waterflooding is relatively inexpensive and easy to control, but waterflooding recovery efficiency is low for high viscosity oil due to the adverse mobility ratio between oil and injected water in high viscosity heavy oil fiehls. Previous studies showed that capillary forces often neglected due to high oil viscosity are important even in the heavy oil systems. At low injection rates, water imbibitions can be used to improve oil recovery. Therefnre waterflooding could become a viable technique for non-thermal enhanced oil recovery, even in the fields with very high oil viscosity. It is recently found that the methods improving the waterilooding recovery efficiency by augmenting the capillary forces to inhibiting bypass flow of injection water on macroscopic or microscopic heterogeneity are also applicable to the sandstone reservoir, heavy oil reservoir, and the polymer flooding. On the basis of the principle of oil reservoir physical chemistry and pore-doublet model proposed, the effects of the injection rate and wettability to the capillary imbibitions are studied, the some conventional viewpoint in some oil reservoir textbooks is considered probably questionable. The results indicate that the injection rate control and the wettability alteration from oil-wet to water-wet conditions are the technical key of the method