煤层气流固耦合渗流模型求解过程中的参数处理

HANDLING OF PARAMETERS IN PROCESS OF SOLVING FLUID-SOLID COUPLING PERCOLATION MODEL OF COAL-BED GAS

在对煤层气的流固耦合渗流模型的求解过程中,总体上采用显式交替耦合求解的方法进行,其实现过程为:煤岩变形场方程的求解滞后于煤层气渗流力学模型求解一个时间步。具体来说,首先对有限差分后的流体渗流场方程进行求解,然后将求得的孔隙流体压力增量传递给煤岩变形场方程,煤岩变形场方程将计算所得的体积应变和应力变化再传给渗流模型,据此对物性参数(孔隙度、渗透率、孔隙压缩系数)进行修改,继而进行下一时间步长的计算,如此反复进行,直至结束。流固耦合渗流数学模型采用IMPES方法进行求解中,对于计算过程的非线性问题表现在时间取值问题和空间取值问题两个方面,对此应采用显式方法进行线性化处理。

Explicit alternative coupling method is commonly used to solve fluid-solid coupling percolation model of coal-bed gas. Its realization process is characterized by that deformation field equation of coal rock is always one time step behind percolation model of coal-bed gas in the process of solving. To be specific, the fluid percolation equation after finite difference is first solved. Then the incremental pore fluid pressure obtained is transferred to deformation field equation of coal rock, which in turn transfers the calculated volumetric strain and stress variation to the percolation model. After the petrophysical parameters, such as porosity, permeability and pore compressibility coefficient, are corrected, the next time step will begin. This process will repeat such in this way till it comes to an end. When IMPES method is used to solve fluid-solid coupling percolation mathematical model, the nonlinear problem in the process of calculation will be reflected in value selection of time and space, which should be solved through linearization with explicit method.