Well Testing Interpretation Model And Productivity Characteristic Of Fractured Horizontal Wells In Fractal Fractured Shale Gas Reservoirs

The recoverable reserves of shale gas in China is huge,economically and efficiently mining of shale gas can effectively reduce the China's oil dependence on foreign.At present,horizontal well drilling and reservoir fracturing are key technologies for shale gas exploitation,which can greatly increase shale gas production rate and cumulative production.Establishing a set of well test interpretation theories for fractured horizontal wells in shale gas reservoirs can provide theoretical support for the calculation of the dynamic parameters and the making exploitation plans in shale gas reservoirs.According to the law of fracture distribution in shale gas reservoirs,three different types of well test models suitable for analytical and numerical solutions are established,respectively.Firstly,based on the assumption of continuity,a well test model for multiple fractured horizontal wells in a fractal dual-porosity shale gas reservoir was established.The solution to the model was obtained through Laplace transform,point source solution,and pressure drop superposition principles.The characteristics of pressure and production curves of multiple fractured horizontal well in fractal dual-porosity shale gas reservoirs and the influence of parameters,such as fractal index,fractal dimension,on pressure and production curves were analyzed.Secondly,based on the fractal statistics theory,the fractal discrete fracture network model and parameter calculation method are studied.The results show that the fractal parameters,such as the fracture center distribution dimension,have good control over the characteristics of well test curves,so the fractal discrete fracture network can be used for well test interpretation in fractured oil/gas reservoirs.Then,on the basis of the fractal discrete fracture network model,considering the main flow mechanisms such as adsorption,desorption and viscous flow in shale gas reservoirs,a well test model of multiple fractured horizontal well in fractal fractured shale gas reservoirs is established.The solution of the model is obtained by embedded discrete fracture model and finite difference method.The characteristics of pressure response and parameter sensitivity of the multiple fractured horizontal well in a fractal discrete fractured shale gas reservoir are analyzed.Finally,considering multiple flow mechanisms such as viscous flow,adsorption/desorption,diffusion flow,and fracture stress sensitivity in shale gas reservoirs,a well testing and productivity evaluation model for volumetric fractured horizontal well in complex boundaries shale gas reservoirs was established.The solution of the composite model was obtained by boundary element method.The correctness and practicability of the model were verified by analytical solutions,commercial software and actual field data.