The Study On Storage And Permeability Model Of Karst Reservoir In Gaoshiti-Moxi Dengying Formation

The Dengying Formation gas reservoir of Gaoshiti Moxi Sinian system in Central Sichuan is the largest marine carbonate gas reservoir in China at present.It is of old age and complex structure.Under various geological actions such as sedimentation,structure and karst reconstruction,the reservoir space types are diverse,with large scale difference,strong heterogeneity,and complex distribution law and seepage characteristics of reservoir and permeability body.On the basis of previous studies,this paper summarizes and studies the geological characteristics of epikarst and buried karst reservoirs in the study area.Based on the well,according to the different types of reservoir space in the reservoir and permeability body connected with the well,three main reservoir and permeability models are determined in the study area,including the drilling karst model,the connected karst model and the buried karst model.In this paper,the seepage analysis of three storage and permeability modes is carried out by using the method of sequential steady-state replacement,the pressure cumulative production curve of three storage and permeability modes is studied in combination with the production dynamic characteristics.All production wells in the study area are classified according to the geological characteristics.There are three dominant zones of karst caves in the platform margin zone of the study area.The karst cave system is greatly affected by the ancient landform,and it is distributed from east to west,obviously coincident with the decline direction of paleotectonic contour lineThe karst cave system is the most favorable reservoir space in the study area,but the combination of karst cave system,small-scale karst cave and matrix pore leads to the complex seepage process.Therefore,this paper uses the numerical simulation method to simulate the seepage mechanism of the drilling karst cave mode and the connected karst cave mode,and discusses the different porosity and permeability in the karst cave,different production well types,and different reservoir reconstruction degrees.The influence of the process can provide reasonable suggestions for how to develop gas reservoirs efficiently in the later stage,and also has certain reference significance for the study of the development mode and seepage characteristics of the same type of carbonate reservoirs...