稠油降黏剂驱提高采收率机理

为系统研究降黏剂驱这一新的开发方式提高采收率机理,应用单管填砂驱油模型、三维填砂驱油模型和微观玻璃刻蚀驱油模型,测试降黏剂驱的驱油效率和波及系数,并对其原因进行分析。实验结果表明,降黏剂驱通过提高驱油效率和增加波及系数提高采收率。与水驱相比,降黏剂驱可提高驱油效率13%,其机理为:①分散乳化,形成水包油的小油滴,有利于通过狭窄的喉道,降低原油的表观黏度;②降低界面张力,增加毛管数,降低残余油饱和度。同时,降黏剂驱将波及系数由水驱时18.8%提高到39.9%,其机理为:①乳液调驱,分散乳化的原油进入水窜通道,水渗流面积减小、阻力增加,后续注入液进入以前未波及区域;②贾敏效应,降黏乳化小油滴聚并成大油滴堵在孔喉处,周围驱替液转向。研究明晰了降黏剂驱提高采收率机理,为后续开发技术界限研究及现场应用奠定基础。

EOR mechanism of viscosity reducer flooding in heavy oil reservoirs

In order to systematically study the mechanism of enhanced oil recovery(EOR)of viscosity reducer flooding,which is a new development method,a single-tube sand-packed model,a three-dimensional sand-packed model,and a mi croscopic glass etching model were used to test the oil displacement efficiency and the sweep efficiency of the viscosity re ducer flooding,and analyze its causes.The experimental results show that the viscosity reducer flooding enhances oil recov ery by increasing the oil displacement efficiency and the sweep efficiency.Compared with water flooding,the viscosity re ducer flooding improves the oil displacement efficiency by 13%,and the mechanisms are as follows:①the crude oil is dis persed and emulsified to form small oil-in-water droplets,which is conducive to reducing the apparent viscosity of crude oil through a narrow throat;②the interfacial tension is reduced,the number of capillaries is increased,and the residual oil saturation is reduced.Simultaneously,the viscosity reducer flooding increases the sweep efficiency from 18.8%to 39.9%.The mechanisms are as follows:①emulsion profile control and flooding.The dispersed and emulsified crude oil enters the water channeling channel,which causes the water percolation area to decrease and the resistance to increase,and the subse quent injected liquid enters the previously unswept area;②Jamin effect.The small viscosity-reduced and emulsified oil drops aggregate to form large oil drops blocked at the throat,and the surrounding displacement fluid turns.This study clari fies the EOR mechanism of viscosity reducer flooding,and lays the foundation for the subsequent studies of the develop ment technical limit and field application.