Study And Application Of Production Evaluation Method For Hydraulic Fractured Horizontal Well In Shale Gas Reservoir

Multi fractured horizontal wells(MFHWs)is the most key technology for shale gas development,which is widely used in the field.Multi-scale flow mechanism and very complex fracture system result the nonlinearity in flow equations and inaccuracy to evaluate the production.So,it is very meaningful and of great significance for shale gas development to build a mathematical model to analyze the productivity accurately.Firstly,the nonlinear flow mechanism is fully analyzed.Gas property parameters(like viscosity,Z-factor and compressibility),adsorption,diffusion and non-Darcy effect vary with pressure and they are characterized quantitatively.Then,with consideration of all these nonlinearity,the five-region model and complex fracture model are built.For most of the wells which lack of micro seismic data,fractures could be simplified and it is suitable to use the five-region model.On the other hand,for those with micro seismic data,fractures could be described accurately and it is suitable to use the complex fracture model.In the five-region model,bi-wings fractures are assumed,nonlinear parameters are processed explicitly and the equations are solved with finite difference method directly to obtain type curve.In the complex fracture model,Green function and superposition method are adopted to describe the flow in the reservoir and finite difference method is used to solve the equations of one-dimensional flow in fracture system.Combining the equations in reservoir and fracture system,the solution in Laplace domain is gained,and it can be transferred to real domain with Stehfest algorithm.Furthermore,the production evaluation method is built with the five-region model and the complex fracture model.Lastly,Production and production composition are analyzed to study the influence of nonlinear parameters,the main factors for production and characteristic of type curves.On the basis of nonlinear flow mechanism and complex fracture system,the mathematical model for shale gas flow in MFHWs is built which forms the semi-analytical and numerical method to evaluate the production.This method we built can handle the cases with or without data of fractures(micro seismic data),analyze production and production composition accurately and instruct for the field case analysis.