Production Performance Analysis And Numerical Simulation For Multistage Fractured Horizontal Well

Hydraulic fracturing is the most important tool to develop tight oil and gas.Due to the complex fracture networks and various flow mechanism in different kinds of reservoir,limits exist when using the former proposed production performance and numerical simulation methods to analyze well production in real field.In order to realize the effective evaluation of tight oil/gas performance,a set of semi-analytical and numerical methods are presented in this paper.First of all,for single,double continuum,and triple continuum media reservoir after fracturing,the semi-analytical method is proposed to anylyze the transient rate and pressure behavior.The source function method,Laplace transform,superposition principle,and numerical discretization method are used integrately.Type curves are given for different models.Based on the field micro seismic map,the composite reservoir models are proposed,which concludes circular composite and elliptical composite models.Single,double continuum,and triple continuum models are all considered.A new linear source function is used to solve the circular composite reservoir,and the elliptical composite model is solved by Mathieu function.Typical flow curves are obtained.Secondly,considering the limits of semi analytical and analytical method which can only solve a specific physical model,the numerical simulation method based on PEBI grid is estabilished.A hybrid method of numerical simulation considering natural fracture and hydraulic fracture is shown in which natural fractures and hydraulic fracture are treated separately.The natural fractures are taken as continuum medium,and hydraulic fractures are taken as discrete ones.The flow from matrix to natural fractures can be a pseudosteady or nonsteady flow model,and the adaptability of the two models is analyzed.Thirdly,considering the low flow non-Darcy flow in tight oil,the simulation program of PEBI grid based on discrete fracture model is estabilished.Both single phase and two-phase flow are considered in the simulator.The convergence properties are analyzed for Darcy flow,nonlinear flow and Pseudo TPG flow model.Nonlinear Flow Embeded Discreted Fractured Model is proposed.The hydraulic fracture and natural fracture are treated as embedded discrete fractures.Both single phase and two phase numerical simulation are developed and the simulation efficiency is enhanced.Multiple transport mechanisms coexist in nanopores of shale gas reservoirs including continuum flow,slip flow,transition flow,and surface diffusion for shale gas.Considering all those transport mechanism,the simulation workflow proposed in the former part is used in the “dual porosity” model shale gas reservoir and the related sensitivity of different parameters are analyzed.Finally,the numerical simulator is coupled with ES-MDA(Ensemble Smoother with Multiple Data Assimilation)successfully to form the history matching tool for tight oil and gas,and is verified by two examples.The history matching tool and simulator can be used in uncertainty analysis for tight oil and gas which provides a new way for tight oil and gas production performance analysis.