The Distribution Of Karst Reservoir And Permeable Body Of The Fourth Member Of Dengying Fm In Gaoshiti-moxi Area

Although the current research has realized that the fourth member of Dengying formation is due to the superimposed karst transformation of the dolomite facies,the research is still unclear about the development and distribution of the reservoir,which limits the further efficient development.And in the previous research on karst reservoirs,it has not been clarified that the reservoir and permeable body is the concept of development direction.Based on the existing reservoir characteristics,comprehensive utilization of field profiles,cores,flakes,logging,production,well test and other data are used to describe the characteristics of the reservoir and permeable body,and explore the distribution law of the karst reservoirs in the Gaoshiti-Moxi block.The research indicates that:(1)The fourth member of the Dengying carbonate reservoir has strong heterogeneity.The reservoir development is mainly affected by sedimentary diagenesis and karstification,and the sedimentary facies,lithology and diagenesis of the fourth member of the Dengying Formation The research shows that the four-segment reservoir space is mainly affected by epigenetic karst and burial karst.The epigenetic karst control the reservoir and permeable body distribution,and the large caves and pores that epigenetic karst formed provide room for the fluids needed for burial karst.Complex corrosive fluids are further superimposed and dissolved around large surface-dissolving pores.(2)By comparing the characteristics of reservoirs and reservoirs,this paper firstly uses dynamic and static methods to describe the characteristics of the four-stage karst reservoirs.Statically,the single-well reservoir is divided into several wells to determine the longitudinal distribution law.The dynamic seepage characteristics of the single well in the fouth member of Dengying gas reservoirs are used to demonstrate that the main seepage characteristics are layered plane radial flow,and the sequential steady-state replacement method is adopted.Determine the extent of pressure fluctuations in the production process,and then reflect the scale of the distribution of the reservoir.(3)Through the production data,well test interpretation,well logging interpretation and core rock sample analysis of the study area,this paper determines the dynamic reserve as a main indicator to evaluate the reservoir and permeable body in the fourth member of Dengying Formation.(4)A method for determining the geological understanding of carbonate rock production characteristics in the study area was initially determined.Through the analysis of the production dynamics and seepage characteristics of single wells such as Gaoshi 3 well,and the comparative study of plane permeability and vertical permeability,it is considered that the reservoir production of Dengying Formation in the study area is mainly layered radial flow,and the layered pore-cave reservoir is continuously development.The production characteristics of 12 typical wells in the study area were analyzed.The dynamic production characteristics of buried karst reservoirs were described by sequential steady-state method and pressure drop method,and the existence of large-scale karst cave system in the study area was demonstrated.(5)The tectonic evolution process of the Dengying Formation is relatively flat,mainly based on stratigraphic lifting,and the development of periodic epigenetic karst caves in the fourth member of Dengying Fm can be observed.Through the division of single well reservoir and permeable body and the comparison of interwell reservoir and permeable body,combined with the production dynamic analysis,it is considered that the karst formed by the epigenetic karst plays a decisive role in the distribution of the reservoir.The complex fluid in the buried karst period is further superimposed around the dominant channel.A number of evidences indicate that the reservoir and permeable bodys are layered over the plane.