Micro-tomography of oil recovery dynamics at a pore scale

原油开采涉及多孔介质中的多相流动。近年来，微聚焦x射线CT扫描仪的快速发展使我们能够在孔隙尺度上可视化和观察相间界面的迁移。在这项研究中，我们可视化了在孔隙尺度分辨率下由毛细和润湿性控制的油和水的两相流动。首先是分离过程，通过毛细管作用将油团从连续体中分离出来，并将其困在多孔介质中，从而降低了石油采收率。接下来，被困油团周围的流场被可视化。水甚至在靠近被困油团的孔隙处流动。而厚度小于孔隙尺度的滞水膜则将油团与流动的水分离开来。基于晶格玻尔兹曼方法开发了多孔介质中两相流的数值模拟程序。对x射线CT成像的多孔结构进行了数值模拟。

Crude oil production from reservoirs involves multiphase flow in porous media. Recent rapid development in micro-focused X-ray CT scanners allows us to visualize and observe the migration of the interfaces between phases at a pore scale. In this study, we visualize two-phase flows of oil and water which is governed by the capillarity and wettability at a pore scale resolution. First the snap-off process that disconnects oil blobs from the continuum to be trapped in a porous medium by capillarity and reduces oil recovery. Next the flow field around the trapped oil blobs is visualized. Water is flowing even at the pores just proximate to trapped oil blobs. However, the stagnant water films which thickness is lower than the pore scale separate oil blob and flowing water. We developed a numerical simulation code of two phase flow in porous media based on the lattice Boltzmann method. Numerical simulations were carried out for porous structures which were obtained by X-ray CT.