Study On Performance Of Fractured Well With Complex Hydraulic Fractures In Shale Gas Reservoir

There is rich resource and broad prospect of shale gas in the world.Hydraulic fracturing is one key technology to achieve the commercial exploitation of shale gas reservoir.Productivity evaluation method is one of the effective means of optimizing fracturing design.Because of the multi-scale storage and flow space from nanopore to microcrack to fracturing fracture in shale gas reservoir,there are many complicated flow mechanisms in shale gas reservoir,such as gas slipping,gas diffusion and gas adsorption and desorption,and complex hydraulic fractures are created after fracturing.That is a challenge to accurately evaluate the productivity of shale gas fractured well and to optimize fracture parameters and decreases the effectiveness of fracturing design for shale gas reservoir.There is limitation of research on performance simulation of fractured well in shale gas reservoir at home and abroad.The influence of shale gas migration mechanism and complex fracturing fracture on shale gas production is insufficiently understanded.In this paper,considering the complicated flow mechanisms of shale gas and the complex geometry of hydraulic fracture,the performance of shale gas fractured well is studied.The following results are obtained:In this paper,considering the real shale pore structure,adsorption and desorption,slippage,Knudsen diffusion and surface diffusion of shale gas,based on the fractal geometry theory,Hagen-Poiseuille law and Langmuir adsorption law,a gas flow mathematical model for shale nanopores is established.Then,a new apparent permeability model is deduced based on Darcy's law,which is closely related to parameters of pore structure,and the model is numerically solved.The nonlinear flow behavior characteristics of shale gas are analyzed,including the influence of fractal dimension and surface diffusion coefficient on apparent permeability.On the basis of the apparent permeability model,considering complicated flow mechanisms in shale gas reservoir,the continuity equation of shale gas reservoir is established and the point source function is deduced for infinite reservior and closed boundary reservior.Considering variable width and penneability nonuniform distribution of hydraulic fracture,and the continuity equation of shale gas reservoir is solved by point source function after discreting the fracture.A plane fracture model and a non-plane complex fracture model are established and the numerical solution scheme is deduced.The distribution of plane fracture flow is obtained by computer programming.The influence of different gas migration mechanisms on shale gas production is analyzed.Based on the plane fracture model,production simulation models for multi-cluster fractured horizontal well(MFHW)and zipper fractured horizontal well are established considering pressure interference between fractures.Based on the non-planar complex fracture model,a vertical well production model with complex fractures and a horizontal well production model with complex fractures are established.All the models are numerically solved by matrix analysis method.The well production under different fracturing modes and fracture geometry is simulated.The effects of cluster spacing,stimulated reservoir volume(SRV)and fracture network parameters on production of fractured wells in shale gas reservoirs are analyzed.The suggestions for optimal fracturing design for shale gas reservoirs are given.The achievements of this study can provide theoretical guidance for optimal fracturing design and efficient development of shale gas reservoir.