孔隙网络模拟渗流速度对页岩气开采的影响

孔隙网络模型是预测多孔介质流动特性的有效手段。基于页岩气藏微观孔喉参数建立了随机孔隙网络模型,并模拟了气水两相流动,通过求解模型压力矩阵方程,绘制渗流图像;通过模拟不同速度下的渗流特征,分析了水侵现象、渗流速度对气水两相渗流路径的影响。结果表明,渗流速度与驱替压差呈正相关,在渗流速度大于临界流速v_c的驱替过程中,压降梯度对渗流路径起主要影响作用,不同的渗流速度会形成不同的渗流路径,渗流路径符合分形特征;而由于较高渗流速度（大于临界流速v_c）会破坏气/水界面稳定性,因此,高渗流速度更利于水侵而降低页岩气产量;若渗流速度小于临界流速v_c,气/水界面趋于稳定,促使页岩气大量产出。

Influence of Seepage Velocity on Shale Gas Exploration by Pore Network Simulation

Pore network model is an effective method to predict the flow characteristics of porous media. Based on characteristic values of shale gas reservoir, a pore network was established. And gas-water phase flow was simulated in that pore network. Seepage image was drawn by solving the pressure matrix equations of the model. By simulating flow under different velocities, the water penetration and seepage path were analyzed. As the results shows, the seepage velocity was positively correlated with the displacement pressure difference. When seepage velocity is higher than critical velocity v_c, pressure drop gradient has a main effect on the seepage path, which conforms to characteristics of fractal curve, and seepage velocity has an effect on stability of oil-gas interface and destroys equilibrium of gas/water interface thus facilitates water penetration and reduce gas production when it's high. There will be a stable gas/water interface and a large amount of gas production when seepage velocity is lower than v_c.