Study On The Characteristics Of Karst Reservoir In Chuanzhong Area Of Sichuan Basin

This paper takes the Permian Maokou Formation in the Chuanzhong area of the Sichuan Basin as a research unit.The method of sedimentology,reservoir geology and other disciplines were used combined with regional geological datas,logging,core,thin slices and seismic datas.Based on the comprehensive analysis,the Lower Permian strata,sedimentary facies,reservoir characteristics and reservoir favorable area distribution in the central Sichuan Basin were studied.The tectonic movement controlling the sediments of the Maokou Formation in Chuanzhong area of the Sichuan Basin was Tungwu movement between the Middle and Late Permian,forming a parallel unconformity between the Maokou Formation and the Upper Longtan Formation.In this study area,the main formation of the Mao 1 to Mao 3 is deposited.The Mao 4 formation is basically ablated.And the residual thickness of Maokou Formation has the characteristics of southwest thick northeast thin.According to the main marks of sedimentary facies such as lithology,sedimentary characteristics and logging characteristics,the sedimentary facies of the Maokou Formation in the study area were studied.In the area,the Permian Maokou Formation is a set of transgressive-ocean-deposited sediments,and the carbonate facies is developed as a whole.The Mao 1 formation mainly develops a set of deep-water platform sediments.The sedimentary submicron is mainly the With Taiwan depression.The Mao 2-Mao 3 formation is developed in the shallow water platform,and the sedimentary microfacies are mainly grain banks and beach interact.Through the observation and analysis of core,well logging datas and thin slice datas,the reservoir characteristics are studied from the aspects of reservoir petrological characteristics,reservoir space type characteristics,physical property characteristics,diagenesis and logging response characteristics.The reservoirs of the Maokou Formation in the area are mainly limestone reservoirs and dolomite reservoirs,mainly composed of granular limestone and crystalline dolomite.The types of reservoir space are mainly intercrystalline pores,caves and cracks.The reservoir's porosity and permeability are low,and it is a low porosity and low permeability reservoir with strong heterogeneity.The reservoirs in the study area are mainly developed in the Mao 3 and Mao 2 formation,and the Mao 1 section is basically not developed.Seismic attribute analysis can reflect the different characteristics of reservoirs and play an important role in reservoir prediction.However,the application of single attributes for reservoir prediction often has problems of multi-solvability.Therefore,this paper conducts seismic multi-attribute analysis and reduces its multiplicity effectively.For the Maokou Formation reservoir,the well-seismic combined amplitude attribute analysis and post-stack constrained sparse pulse inversion are mainly carried out,and the technical methods and implementation process are elaborated.Finally,through the practical application,the prediction of the distribution of the surface layer and the inner reservoir of the Maokou Formation were realized.And the reservoir development model was identified and summarized through the seismic data.