Productivity Simulation Study Of Fractured Horizontal Wells In Low Permeability Oil Reservoirs

The reserves of low permeability oil reservoirs are huge in our country,and the development of low permeability reservoirs has gradually become the main body of oil and gas fields development in recent years.With the development and application of horizontal wells fracturing technology,the productivity simulation and prediction of fractured horizontal wells in low permeability oil reservoirs is more and more important for the efficient development of oil and gas fields.Scholars and specialists from all over the world have done extensive researches on the productivity of fractured horizontal wells mainly by the analytical method,numerical simulation method and semi-analytical method.However,the current productivity models do not sufficiently consider threshold pressure gradient,stress sensitivity,natural fracture,and so on.In view of the characteristics of low permeability oil reservoirs and fractured horizontal wells,this paper has carried out the productivity model study of fractured horizontal wells in low permeability oil reservoirs,and the main work completed are as follows:(1)Through a large amount of literature at home and abroad,the current status of fractured horizontal wells’ seepage model and productivity,the geological characteristics and seepage characteristics of low permeability reservoirs are summarized,meanwhile,the hydraulic fracture morphology,the interference between hydraulic fractures and seepage characteristics of fractured horizontal wells are analyzed.(2)Based on the theory of dual medium seepage,considering threshold pressure gradient,stress sensitivity,the angle of hydraulic fractures,the interference between hydraulic fractures,the flow conductivity of hydraulic fractures,and other factors,applying Laplace transform,Stehfest numerical inversion,superposition principle,Duhamel theorem,perturbation theory and the basic theory of point source function,an unsteady seepage mathematical model and productivity model of fractured horizontal wells in low permeability oil reservoirs is established,and a semi-analytical solution of model is obtained.(3)The typical log-log modern well test curves and dimensionless productivity curves are plotted by matlab program simulation calculation,then the seepage characteristics and the productivity influence factors of fractured horizontal wells in low permeability oil reservoirs are analyzed.(4)Combined with field case,the productivity model established in this paper is calculated and proved to be accurate;the influence of different hydraulic fracture distributions on the production of fractured horizontal wells in low permeability oil reservoirs are calculated and analyzed,which provide some reasonable suggestions for the optimum design of hydraulic fracture distributions.Comprehensively considering threshold pressure gradient,stress sensitivity and natural fracture in low permeability reservoirs,and the angle of hydraulic fractures,the interference between hydraulic fractures and the flow conductivity of hydraulic fractures in fractured horizontal wells,this paper has established a new productivity model of fractured horizontal wells in low permeability oil reservoirs,which has certain innovation.The work of this paper has improved the understanding of seepage rule for fractured horizontal wells in low permeability reservoir,and has some guiding significance for the fracturing operation.