可视化微观孔隙模型中气水两相渗流机理

Gas-water two-phase flow mechanism in visual microscopic pore model

采用激光刻蚀的均质微观孔隙模型对低渗透油气藏岩心进行了气水两相渗流试验。模型亲水,驱替基质为蒸馏水加甲基红,气体为氮气。研究结果表明:在驱替压差不大的情况下,无论是孔隙还是喉道,气水分布及流动方式主要为水包气,水沿管壁流动,气体在孔道中央流动;水驱气过程中封闭气的形成方式主要有绕流形成的封闭气、卡断形成的封闭气、孔隙盲端和角隅形成的封闭气、"H型"孔道形成的封闭气;同时,水锁也是多孔介质中两相渗流的主要特征,可以通过降低压力使气体充分膨胀和提高驱替压差来提高采收率,降低封闭气量。

A series of gas-water two-phase flow experiments in low permeability cores were conducted by using laser etched microscopic pore model. The model was water-wet system. Flooding medium was distilled water added by methyl red, while gas was nitrogen. Research results show that gas and water distribution and flow patterns in both pores and throats are mainly aerated water in lower drive pressure circumstances. The water flows along the wall and the gas flows in the central channels. The water invasion results in the trapped gas, and five main reasons are circumfluence, cut off phenomenon, unconnected pores or blind corners and “H” channels. The water lock also is the major feature of two-phase flow in porous medium. In heterogeneous model, gas recovery can be enhanced by reducing gas pressure or raising drive pressure drawdown.