| With the recent development of oil industry and the need of solving complicated petroleum engineering problems, fluid-solid coupling study which is highly valued is becoming more and more important in oil drilling ^ oil production and oil development. In order to accurately predict production process on the oil-gas field > simulate fluid flowing process and reveal fluid distribution regularity, multiphase seepage flow derived from water injection and production process, change of stress state and coupling effect amongst reservoir distribution must be taken into consideration.On the basis of a great number of experiments and theoretical studies performed by former researchers, the work finished in this paper concerning fluid-solid coupling theory in low permeability reservoir focuses on several aspects of the following:1. According to the basic conception of fluid-solid coupling seepage flow theory, an equation of motion should be founded. Moreover, depending on mass conservation law, combing geomechanics seepage mechanics and rock mechanics, considering start-up pressure gradient and seepage flow characteristics while seeping in low permeability reservoir, then fluid-solid coupling multiphase and polycomponent seepage mathematical model in changeable low permeable and porous media is established, which includes basic differential equation of fluid-solid coupling seepage and its subsidiary equation needed when extracting an answer. Fluid-solid coupling black oil model and oil-water two-phase seepage mathematic model are captured by simplifying fluid-solid multiphase and polycomponent seepage mathematical model.2. Based on the analysis of rock stress and strain, combining effective stress principle and rock matrix constitutive relation, establishing mathematical model of rock matrix in low permeability reservoir including porosity equations, balance equations, geometrical equations and rock matrix constitutive relations, etc. Fluid-solid coupling model of multiphase (oil, gas, water) seepage are composed of solid phase balance equations and fluid black oil model. They contains coupling factors each other and also depends on each other, which are a group of partial differential equations solved by coupling.3. As to the elastic plastic distortion characteristics under the condition of changeable stress in low permeability reservoir, elastic reservoir and elastic plastic reservoir constitutive model are established and corresponding matrix description and matrix expressions are given, either.4. Calculation model of capillary pressure and relative permeability is given by combining specific characteristics in low permeability reservoir. Theoretical calculation model of dynamic variation on porosity, permeability and the like physical parameters needed when solving fluid-solid numerical simulation in low permeability reservoir is given through summarizing former results of physical parameters dynamic model, meanwhile, a dynamic model of computing start-up pressure gradient is given.5. Systematically studying fluid-solid coupling mathematical model of iterative coupling decoupled coupling and fully coupled numerical solution technique in low permeability reservoir.Numerical solution method of iterative coupling is: adopt explicit alternating solution method, that is, rockdistortion mathematical model lag behind seepage mathematical model just one-step time. Fluid seepage mathematical model is solved by using block center finite difference method, oil-water two-phase fluid seepage equation belonging to the model adopts IMPES method, that is, adopting implicit method to solve reservoir pressure and explicit method to solve fluid saturation, oil-gas-water triphase seepage equations are solved by using SEQ sequence, and also analyzes fluid and well parameters, equation group is solved by using orthomin method, whereas rock distortion mathematical model is solved by using finite element method. According to the basic principle of finite element method, on the basis of establishing d...
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