稠油油藏CO2泡沫启动残余油机制的可视化实验

国内外对于CO₂泡沫与稠油作用的理论研究已相对成熟,但能直观表现CO₂泡沫在驱替稠油过程中对残余油的启动过程以及作用方式的可视化研究较少,为了进一步探究CO₂泡沫与稠油的作用机理,利用自制二维平面模型,通过可视化实验驱替系统开展了CO₂泡沫在驱替过程中对残余稠油启动效果的微观动态实验研究,观察了启动盲端残余油、剥蚀油膜、段塞前端乳化驱油等过程;利用高温高压配样装置,开展了CO₂泡沫体系作用下稠油的PVT实验。温度从30℃升至90℃,气体溶解度变化不大;稠油体积因子由1.19上升至1.42;降黏率由13.55%上升至67.42%。一方面,CO₂泡沫选择性封堵大孔道、启动残余油的微观作用;另一方面,CO₂泡沫流体降低了驱替系统的流度比。这两者的共同作用,使得CO₂泡沫流体具有改善波及体积、增加驱油效率的效果。

Experimental Study on Mechanism of CO2 Foam Starting Residual Heavy Oil

Domestic and foreign theoretical studies on the effect of CO₂ foam on heavy oil have been relatively mature,but there are few visualized studies on the start-up process and action mode of CO₂ foam on residual oil in the process of displacement of heavy oil.In order to further explore the mechanism of action between CO₂ foam and heavy oil,micro-dynamic experimental study on the start-up effect of CO₂ foam on residual heavy oil in the process of displacement was carried out by using self-made two-dimensional plane model and visual experimental displacement system.The process of starting the residual oil at the blind end,eroding the oil film,and emulsifying and displacing the oil at the front end of the slug were observed.Using a high-temperature and high-pressure sample preparation device,PVT experiment of heavy oil under the action of the CO₂ foam system was carried out.With the temperature rising from 30℃to 90℃,the solubility of CO₂ in the heavy oil changed little,the heavy oil volume factor increased from 1.19 to 1.42,and the viscosity reduction rate increased from 13.55%to 67.42%.On the one hand,the CO₂ foam had the microscopic effect of selectively blocking the large pores and starting residual oil;on the other hand,CO₂ foam fluid reduced the mobility ratio of the displacement system,which made CO₂ foam fluid had the effect of improving the swept area and increasing the displacement efficiency of improving swept area.