低渗透气藏流——固耦合渗流数值模拟

NUMERAL SIMULATION OF FLUID SOLID COUPLING PERCOLATION IN GAS RESERVOIRS WITH LOW PERMEABILITY

对于低渗透气藏,压力变化引起的介质变形导致储层孔隙度、渗透率变化明显,对气藏开发动态有较大的影响,并且低渗透气藏的流—固耦合效应较中高渗透率气藏强得多。因此,在低渗透气藏模拟中考虑流—固耦合效应可以合理地预测气藏开发动态。此外,由于低渗透气藏渗流机制的特殊性,其渗流曲线偏离达西定律,且存在启动压力梯度,造成低渗气藏的耦合模拟更加复杂。文章基于对低渗透气藏储层特征及渗流机理的认识,将渗流力学和弹塑性力学相结合,建立了低渗透气藏流—固耦合渗流数学模型、数值模型和模拟模型,并利用该模型对四川某低渗气藏开发过程中储层参数、开发指标的变化进行了模拟计算,还比较了考虑介质变形的耦合模型和不考虑介质变形的刚性模型的计算结果。

In gas reservoirs with low permeability) media deformation caused by overburden pressure leads to remarkable change of porosity and permeability, which affect production performance of the gas reservoirs. The fluid-solid coupling effect of the gas reservoirs with low permeability is much stronger than that of the gas reservoirs with mid/high permeability. So, considering fluid - solid coupling effect, the simulation of gas reservoirs with low permeability can predict the production performance reasonably. Since the percolation mechanism of gas reservoirs with low permeability is special, their percolation curves deviate the Darcy's law and the starting pressure gradient exists, the coupling simulation of gas reservoirs with low permeability is more complicated. Based on the characteristics of gas reservoirs with low permeability and the percolation mechanism, and combining the percolation mechanics with the elasticity - plasticity mechanics, the fluid - solid coupling mathematical model, numeral model, and simulative model are established. With the models, the simulative calculation is conducted for the change of the reservoir parameters and production indexes during production process of someone gas reservoirs with low permeability in Sichuan. And the calculating results of the coupling model with considering media deformation and the rigid model without considering media deformation are compared. Some achievements are obtained.