The Analysis of Coupling Law of Stress field/Seepage field In Low Permeability Reservoir

摘要

In order to forecast the mining process of oil and gas field rightly, simulate the flow process of reservoir fluid accurately and reveal the fluid distribution law, it must be considered that multiphase fluid seepage caused by water injection and exploitation, the change of stress state and the coupling between the reservoir deformations. According to the basic theory of rock mechanics, fluid mechanics in porous medium, geologic mechanics, calculated mechanics and fluid-solid coupling seepage, considering the trigger pressure gradient of seepage flow and fluid-solid coupling characters of low permeability reservoirs, a multi-phase and multi-component seepage flow mathematical model of coupling between stress field and seepage field in low permeability and porous medium reservoir is established. On the basis of the analysis of stress and strain in reservoir rock, combining the principle of effective stress and the relation of rock matrix constitutive, a mathematical model of rock skeleton in low-permeability reservoir is established. Combining the specific features of low permeability reservoir and according to the laboratory results, the theoretical calculation model of dynamic changes of material parameters such as porosity and permeability etc that is established and the dynamic model of computing pressure gradient is given. On this basis, the numerical model of iterative coupling is established, and program design is conducted by coupling numerical computing method combining finite difference with finite element, the analysis of coupling between seepage field and stress field in low permeability reservoir is conducted. By the method of numerical simulation, the variation law of stress-strain with time and space in the progress of depletion type drive for single well, dynamic variation law of petrophysics parameters is studied. It can be seen that the fluid-solid coupling effect in low permeability reservoirs is very obvious through analyzing and comparing to the calculation results of rigid model.