Study On Shale Gas Reservoir Numerical Simulation

America's shale gas revolution successfully changed pattern of world energy,making the whole world starts to pay attention to this promising unconventional gas reservoir.Unlike conventional gas reservoir,shale gas reservoir has characteristics of low porosity and low permeability,which efficiently development needs horizontal drilling and multi-stage hydraulic fracturing.Accurate shale gas reservoir numerical simulation considering horizontal drilling and multi-stage hydraulic fracturing is the basis and premise of its development.The existing shale gas reservoir numerical simulator cannot comprehensively consider shale gas storage and migration mechanisms,which leads the simulation results lack of accuracy and practical value.Therefore,it has important significance to develop a shale gas reservoir numerical simulator which can fully consider shale gas storage and migration mechanisms.Through extensive research of shale gas storage and migration mechanisms,this paper establishes a relatively complete seepage mathematics model.And a shale gas numerical simulation program is developed based on this model.Through the research and application of this program,the following results are obtained:(1)The main factors effect shale gas reservoir productivity include adsorption and desorption,diffusion and slippage in matrix system;the stress effect and high velocity non Darcy effect in fracture system.A comprehensive shale gas reservoir seepage model considering these five factors has been built based on traditional three dimensions one phase gas reservoir model.The numerical solution of this model is solved by the finite difference technique.(2)Detailed summary and classification are carried out,based on the comprehensive understanding of local grid refine technology.Three different kinds of medias exist in shale gas reservoir controlled by different mechanisms have been successfully simulated by applying local grid refine technology in the program.(3)Though comparative analysis,an exciting result has been found that the local grid refine technology takes 10% time used by full refined grid to calculate a similar result.What is more,comparing with the non-refine grid,the local grid refine technology can obtain a much more accurate results with a slight time increase.(4)A comparison of five affecting factor of shale gas production has been carried out.A few results has been made: The early stage shale gas productivity is mainly effect by fracture system,and the later shale gas productivity is influenced by matrix system.The key factors of Each system are adsorption desorption effect in matrix system and stress effect in fracture system.