低渗透气藏流固耦合综合数学模型

An aggregative mathematical model of fluid-solid coupling for low permeability gas reservoir

气藏的开发过程是一个流体渗流与地层岩石变形动态耦合的过程,尤其低渗透气田中,由于受到启动压力梯度、滑脱效应和储层应力敏感等因素的影响,气体渗流规律不再符合经典达西定律,耦合效应也较中—高渗透率气藏强。基于渗流力学、固体力学及Biot孔隙弹性理论,将岩石骨架变形引入固体连续性方程中,并综合考虑储层应力敏感、启动压力梯度及滑脱效应的影响对气体的渗流速度进行修正,建立了低渗透气藏流固耦合渗流数学模型。

The development process of gas reservoirs is a dynamic coupling process of fluid percolation and formation rock deformation, especially in low permeability gas field, where gas percolation doesn’t conform to the classical Darcy law anymore as affected by threshold pressure gradient, slippage effect and reservoir stress sensitivity, and the coupling effect is also more prominent than that in medium-high permeability gas reservoirs. Based on percolation mechanics, solid mechanics and Biot pore elasticity, rock frame deformation is introduced into solid continuity equation; gas flow velocity through porous medium is adjusted with comprehensive consideration of reservoir stress sensitivity, threshold pressure gradient and slippage effect; and a mathematical model of fluid-solid coupling is set up for low permeability gas reservoirs.