Mumerical Test Theory Research Of Fracture-Cavern Carbonatite Gas Reservoir

With the growing demand for energy and improving for petroleum exploration and development,the exploration and development of fracture-cave carbonate reservoirs are taken seriously by all countries.Due to diversity of reservoir space and complexity of seepage law,it was rather difficulty to exploration and development of untraditional reservoirs.The fourth member of the G gas reservoir in Sichuan Basin is a typical fractured-cave carbonate reservoir,which are characterized by residual intergranular pores with 1-4mm pore size,caves and fractures,thin monolayer,large cumulative thickness and strong heterogeneity.Besides,traditional well test theory cannot be applied to fractured-cave reservoir because of the complexity of fluid flow in karst reservoir body.Therefore,based on previous research about well test theory of fracture-cave carbonate oil reservoir,this paper carry out well test theory research.The main research contents of the paper is as follows:(1)Based on G gas reservoir characteristics,the fracture-cave development zone can regard as karst reservoir body,the low porosity and high permeability zone is regard as connected zone,which connected with many karst reservoir bodies of random distribution.(2)It is consider that fracture-cave development zone regard as dual continuum medium model.The laplace solutions of infinite boundary,outer sealed boundary and constant pressure outer boundary have been obtained,and this paper has analyzed the characteristics and influential factors of the typical curves.(3)G gas reservoir characteristics study shows that "fracture-cavity combination"composed of karst reservoir body and connected zone regard as discrete medium model.Established five discrete medium well test models:a single karst reservoir body model,a single karst reservoir body with connected zone model,series karst reservoir body model,a series of karst reservoir body composition model.Besides,this paper has analyzed the characteristics and influential factors of the typical curves.(4)Considering elastic expansion of the karst reservoir body away from wellbore,linear flow of connected zone and near wellbore high speed non-Darcy flow,the paper establish two kinds of discrete medium productivity model:N karst reservoir body composition model and N karst reservoir body fracture composition model.Then,this paper has analyzed the influential factors of the typical inflow performance relationship curve.(5)Selected G7 well as case analysis,the N karst reservoir body composition well test fitting curves are well consonant with measured pressure recovery curve,which interpret basic parameters of each karst reservoir body and connected zone.Then,compared and analysized the theoretical curve of the productivity model and measured data of back pressure test,the results indicate that the theory is reliable and correct because of curve coincide hightly and open flow potential small difference.Finally,through the study of discrete medium well test model,discrete medium productivity model,we can know characteristics and flow dynamic of G gas reservoir better.