Capacity Analysis Of Discrete Fracture Mesh Model For Shale Gas Reservoirs

Horizontal well with massive hydraulic fracturing technology has been widely used to exploit the shale gas reservoirs efficiently. Because of the particularity of shale gas reservoir conditions, sometimes the complex induced fractures can be created during the fracturing process. The flowing mechanism and analysis of productivity of shale gas reservoir has become a difficult spot. The seepage model of fractured reservoir is mainly divided into three categories:the traditional continuous model and the equivalent continuous medium model and the discrete fracture network model. The distribution and characteristic of each fracture can be taken into account in the discrete fracture network model, make it be applicable to the strong heterogeneity shale gas reservoirs.The Finite Element Method(FEM) uses the integral "weak" form to handle the partial differential equations, which makes it more precise than the Finite Difference Method and the Boundary Element Method. Besides, it is easy to handle complex boundary due to the unstructured grid.According to the strong heterogeneity characteristics of shale gas reservoir, a transient percolation mathematical model for multiple fractured horizontal well(MFHW) with complex induced fractures was established based on discrete fracture network model. And also, the solution of the model was obtained by using FEM. The main work conducted in this thesis as follows:(1)Combined with the motion equation, state equation and continuity equation, taking account of adsorption, the basic fluid flow equation and discrete fracture network model fluid flow equation of shale gas reservoir are deduced;(2)Based on the unstructured grid, the Galerkin FEM is used to establish the numerical format;(3)The seepage numerical equation was solved by the successive iterations of the algorithm method. This paper programmed the FEM numerical simulator by MATLAB, and verified the feasibility of the program by comparing with the result of the commercial software Saphir;(4) Appling the FEM numerical simulator to analyze the comprehensive influences of the gas reservoir parameters, fracture parameters and reservoir permeability parameters on the productivity of shale gas reservoir.From the above study, the solutions and results for MFHW with complex fractures based on the discrete fracture network model and FEM in shale gas reservoir are obtained, which have a significant theoretical and practical value for well production performance analysis in unconventional shale gas reservoirs.