Study On Fracture Parameters Optimization Of Horizontal Wells In Tight Sandstone Gas Reservoirs

Tight sandstone gas reservoirs are one of the most important unconventional oil and gas reservoirs.The global tight gas resources are very rich and have great development potential.Compared with conventional oil and gas reservoirs,tight sandstone gas reservoirs have a large number of natural fractures resulting in strong heterogeneity,which also have low permeability and porosity.Now horizontal well multi-fracturing technique has been widely used in low permeability reservoirs,but the production prediction of horizontal wellbore in complex reservoirs has always been a difficult point in the industry.Therefore,this paper studies the numerical simulation on fracturing horizontal well in tight sandstone gas reservoirs and explores the influence of fracture parameters on horizontal well production.According to the theory of unstable gas flow in tight sandstone gas reservoirs and the embedded discrete fracture model,the production dynamic prediction model of staged fracturing horizontal wells in tight sandstone gas reservoirs has been established by using finite difference method.Through research,the main work completed in this paper is as follows:(1)The embedded discrete fracture physical model and mathematical model were established and the conductivity calculation formula of non-neighboring connections was improved to consider the variable flow conductivity through the fractures.(2)The finite difference mathematical model and numerical model of the embedded discrete fracture model of single-phase gas in tight sandstone gas reservoir were established by considering the non-Darcy flow and the stress sensitivity effect in the matrix.Considering the characteristics of heterogeneous reservoirs,natural fractures were randomly generated,and a production prediction model for fractured horizontal wells in natural fractured tight sandstone gas reservoirs was established.(3)Based on Matlab software,a numerical simulator for the embedded discrete fracture model of tight sandstone gas reservoir and a numerical simulator considering natural fractures were developed.The production prediction model of the staged fracturing horizontal well in tight sandstone gas reservoir was verified,and the correctness of the method was illustrated.At the same time,the numerical simulator had the characteristics of fast calculation speed,high precision and wide application range.(4)Taking a well in Hangjinqi area of Ordos Basin as an example,analyze the main controlling factors on the production of horizontal wells in tight sandstone gas reservoirs including the number of fractures,fracture length,fracture spacing and fracture permeability,discuss the effect of different fracture patterns and fracture propagation schemes,optimize the fracture parameters of horizontal wells,and obtain the optimal combination of fracture parameters.Based on the embedded discrete fracture model,the complex natural fractures and artificial fractures are characterized.Starting from the characteristics of tight sandstone gas reservoirs,more realistic factors are considered in the yield calculation model to study the tight sandstone gas.The finite difference numerical simulation method of the embedded discrete fracture model is carried out.The simulation results can effectively evaluate the effect of fracturing,and provide theoretical guidance for the fracturing construction of horizontal wells in tight sandstone gas reservoirs.