Seepage Model Study On Liquid-Solid Coupling Of CH₄-CO₂ Two-component Gas In Shale

The development of shale gas has entered a crucial stage in China,it exists many problems in the exploration technology,development technology and flow mechanism research which are in need of the solution.The development of shale gas reservoirs is usually based on the "Massive hydraulic fracturing+Horizontal wells" development treatments.It is proposed that use supercritical carbon dioxide to strengthen the shale gas efficient development method.So the establishment of a set of carbon dioxide replacement shale gas multi-Coupled seepage theory is imminent.In this paper,the flow-fluid coupling model of CH4-CO2 bicomponent gas in shale is established,which provides a theoretical basis for establishing the above-mentioned seepage theory.Based on the research of domestic and foreign literatures,this paper analyzes the characteristics of shale reservoir media,the migration characteristics of gas in multi-scale porous media and the influence of shale deformation on gas flow,and puts forward the relationship between shale Multi-scale porous media,and the flow characteristics of gas under different pore scales are expounded to establish the fluid-solid coupling seepage flow model of CH4-CO2 two-component gas in shale,and the corresponding computer program The simulation and calculation of the case are carried out to confirm the correctness and validity of the model,method and technology.The acquired achievements are as follws:1.The scheme of gas flow in multi-scale shale of shale is proposed.Based on the analysis of the characteristics of shale reservoir media(pore,fracture and main physical parameters),the characteristics of gas migration in porous media are summarized and summarized.It is found that shale reservoir has special low porosity,Porosity and other characteristics of the pores,and in the shale porous medium gas desorption,diffusion and seepage flow three flow patterns,and then according to the size of the pore diameter shale porosity is divided into matrix nanopores,nano-micron holes and cracks,and elaborated The flow pattern and flow characteristics of the gas at different pore scales.2.The hydrodynamic coupling model of CH4-CO2 bicomponent gas in shale was established.Firstly,a mathematical model of gas flow in porous media with different pore sizes was established according to the scheme of gas flow in multi-scale porous media.The flow equation in nanopores,the flow equation in nanometer pores and the And then the influence of effective stress and matrix shrinkage on the permeability parameters and porosity of shale reservoirs is analyzed on the basis of analyzing the influence of reservoir pressure on the shale gas development process.Finally,coupled with the auxiliary equation,the physical parameters of the coupling equation and the conditions of the solution,together constitute the shale CH4-CO2 two-component gas flow-solid coupling mathematical model.3.The hydrodynamic coupling model of CH4-CO2 two-component gas in shale was established.The finite difference method is used to discretize the mathematical model of the fluid-solid coupling seepage flow.The mesh system adopts the block center grid,and then the resulting difference equation is linearized,and finally the successive line relaxation in the super relaxation method(LSOR)Iterative solution to the linear equation.4.Completed the preparation of the mathematical model calculation program.The calculation results are analyzed by the calculated calculation program,which proves the correctness and validity of the model,method and technology.