Study On Productivity Of Fractured Horizontal Wells In Shale Gas Reservoirs

The shale gas resources are huge in our country,and economically efficient mining can alleviate our country energy supply pressure and play an important role in country sustainable economic development.Compared with conventional oil and gas reservoirs,The shale gas reservoirs differ greatly in the mechanism of accumulation,mode of occurrence,and migration mechanism.The theory of conventional oil and gas reservoirs cannot be directly applied to shale gas reservoirs,and the shale reservoir is extremely dense and has a low permeability.Horizontal wells+multi-stage fracturing are usually used to improve the shale reservoir permeability to increase the productivity of shale gas reservoirs.Fracturing capacity simulation and prediction have important implications for analyzing horizontal well fracturing effects,guiding shale gas reservoir fracturing construction and process parameter optimization.Based on the research of shale gas reservoir production,this paper comprehensively considers reservoir characteristics,complex migration mechanism,hydraulic fracture morphology and seepage characteristics of shale gas reservoirs,and studies the productivity of fracturing horizontal wells in shale gas reservoirs.The main work completed is as follows:(1)Through literature review,the main reservoir space of shale gas reservoirs,the main gas storage methods and multi-scale migration mechanism are discussed.The seepage model and productivity research method of horizontal wells in shale gas reservoirs are summarized,and the hydraulic fracture morphology and seepage characteristics are analyzed.(2)Based on dual medium seepage theory,Comprehensive consideration of adsorption,desorption and diffusion mechanisms(pseudo-steady state and transient diffusion)of shale gas in reservoirs and stress-sensitive effects of natural fractures.Using the point source function theory,Laplace transform,Bessel function and perturbation method to solve the point source solution of the shale reservoir.(3)Considering the limited conductivity of hydraulic fractures,the inclination of fractures,the length of fractures,the mutual interference between fractures,etc.Principle of discrete hydraulic fracture,coordinate transformation and pressure drop superposition are employed to couple shale reservoir point source solution.The shale gas reservoir fracturing horizontal well productivity model is established,and the semi-analytical solution of the model is solved.(4)According to Duhamel's theorem,Considering the skin and wellbore reservoir effects,Through the Stehfest numerical inversion method,MATLAB programming to solve the productivity model,the shale gas reservoir pressure dynamic curve and the dimensionless capacity reduction curve were drawn.And according to the characteristics of the curve,nine flow stages are divided.The effects of shale reservoir parameters(stress sensitivity coefficient,storage ratio,adsorption index,etc.),hydraulic fracture parameters(conducting capacity,length,cluster spacing,etc.)on bottom-hole pressure response and productivity of fractured horizontal wells are analyzed.(5)The reliability of the model is verified by a shale gas well data.On this basis,the hydraulic fracture conductivity,fracture length distribution and fracture spacing are optimized.