页岩中页岩气渗流系数计算模型

Calculation Model for the Permeability Coefficient of Shale Gas in Shale Matrix

依据页岩气在页岩孔隙中的渗流行为,建立了页岩气释放、扩散耦合模型,利用Laplace变换方法,将耦合模型转化为Laplace空间上常微分方程初边值问题,并找到了压力解析解,求得了渗透系数.实例计算验证了渗流模型及解的可靠性,丰富了页岩气不定常渗流理论.

According to the seepage behavior of shale gas in shale matrix,a coupling model for both the shale gas release and diffusion was established. With the Laplace transform method,the coupling model was converted to initial and boundary value problems of ordinary differential equations in the Laplace space. Then the analytical solution of pressure was found,and the permeability coefficient was obtained.The calculation of some specific examples prove reliability of the seepage model and correctness of the solution. The results indicate that the shale gas release process is mainly composed of two actions of adsorption and diffusion,in which the adsorption action has substantial influences on both the effective porosity and the permeability coefficient of the shales. This research enriches the unsteady seepage theory about shale gas.