Study On Flow Model Of Multi-stage Fracturing Horizontal Well In Low Permeability Reservoir

The physical properties of low permeability reservoirs are poor,and the stress sensitivity is common in the development process.Field and laboratory tests show that the stress sensitivity has a great impact on the production performance of low permeability production wells,so it can not be ignored.In order to establish the seepage model of low permeability staged fracturing horizontal well considering the effect of stress sensitivity,the point source function of infinite low permeability reservoir considering stress sensitivity is established by using perturbation transformation and Laplace transformation.Then,the point source functions of closed boundary,constant pressure boundary,mixed boundary and other external boundary conditions are obtained by using the image reflection method.Then,the basic source functions such as line source,area source and plate source are obtained by integrating the above point sources along different directions and ranges.Finally,the unsteady flow model of staged fractured horizontal well in low permeability reservoir under different external boundary conditions is established by using Newman integral and superposition principle.The results of the model are verified by commercial numerical software,and the sensitivity of the key parameters is analyzed.The calculation results show that the effect of stress sensitivity on the production performance of fractured horizontal wells is mainly reflected in the middle and late stage of seepage.Then,the influence rules of fracture half length,fracture spacing,fracture number,fracture penetration ratio and other parameters on the well test curve are analyzed,which provides theoretical support for the fracturing well test analysis of horizontal wells in low permeability reservoirs.Fracture geometry parameters have a great influence on the production of staged fractured horizontal wells in low permeability reservoirs.Reasonable fracture parameters are one of the key factors for scientific and efficient development of low permeability reservoirs.However,the enumeration method,orthogonal experimental design and numerical simulation method used in the optimization of fracture parameters are faced with many problems,such as incomplete parameter coverage,more optimization schemes and heavy workload.In view of the above problems,this paper uses adaptive genetic algorithm to optimize the fracturing parameters of staged fracturing horizontal wells in homogeneous reservoir.The optimization results show that the optimal fracture length distribution is U-shaped with high outside and low inside,the optimal hydraulic fracture spacing distribution is equal spacing distribution,and there are optimal fracture number and fracture size for specific reservoirs.The research results have certain guiding significance for fracturing optimization design of low permeability reservoir.