Research On Single Well Productivity And Influencing Factors In Low-permeability Gas Reservoirs

In China,low-permeability gas reservoirs are widely distributed and abundant reserves.How to efficiently develop low-permeability gas reservoirs has become the focus of petroleum science and technology personnel.But,low-permeability gas reservoirs have low stable production capacity,because it is low porosity,low permeability and strong heterogeneity.Horizontal well technology is one of the important techniques to improve the output of single well,it should be studied.This paper systematically investigates the relevant literatures at home and abroad,and studies the seepage mechanism of low permeability gas reservoirs.These include slippage effects,starting pressure gradients,stress sensitivity and water lock effects.Based on this,the steady horizontal productivity model of conventional horizontal wells is studied,and using the conformal transformation method and the equivalent seepage resistance method,derivation of single-phase capacity formula for horizontal wells in low permeability gas reservoirs which is considering starting pressure gradient and high speed non-Darcy flow effect.The equation was corrected by permeability anisotropy and eccentricity.The factors affecting horizontal well productivity,horizontal length,permeability anisotropy,reservoir thickness and eccentricity were analyzed.Based on the research of conventional horizontal well productivity,considering the reservoir seepage and fracture seepage,a single-phase steady-state capacity model of low-permeability gas reservoir fracturing horizontal wells considering high-speed non-Darcy flow effect is established.The study analyzed the effects of fracture conductivity,half length of cracks,crack spacing and number of cracks on the productivity of fractured horizontal wells.The results show that the greater the fracture conductivity,the greater the productivity,but after the fracture conductivity increases to a certain value,the increase rate of gas production tends to be gentle.The more cracks,the greater the productivity of the fractured horizontal well,and the excessive cracks will interfere with each other,reducing the gas production of a single crack.When the fracture conductivity is relatively large,the longer the fracture,the greater the productivity.The larger the crack spacing,the larger the production capacity,and the limit value of the production capacity after a certain value.Numerical simulation software establishes single well model of horizontal well in low permeability gas reservoir.Production dynamics indicators for unfractured horizontal wells and fractured horizontal wells are predicted,Prove that the horizontal well production after fracturing is much larger than the unfractured horizontal well.This paper optimizes the fracture parameters of fractured horizontal wells.The results show that increasing the number of fracturing sections can effectively increase the gas production,and the growth rate is gradually reduced.It is recommended that the target gas reservoir fracturing 5?7 segments.The increase in crack length can increase the gas production.Considering other influencing factors,it is recommended that the crack control be 300m.The degree of unequal strength fracturing of each section is higher than that of equal-strength fracturing.It is recommended to adopt unequal-strength fracturing of each section.In this paper,the research on the seepage mechanism of low-permeability gas reservoirs and the steady-state productivity of horizontal wells has a certain degree of research significance and application value.