Study On Sedimentary Facies And Reservoir Characteristics Of The Upper Sinian Qigebulake Formation In The Northern Of Tarim Basin

In this paper,the upper sinian qigebulake formation in the northern tarim basin is taken as the research object.Based on the previous research results and guided by the theories of various disciplines,the stratigraphic characteristics,sedimentary facies characteristics,reservoir petrological characteristics,reservoir physical properties,reservoir diagenesis and main control factors of the upper sinian qigebulake formation are studied by making full use of field profile,drilling core,geochemical analysis,logging and seismic data.The results show that:1.The upper sinian qigablaque formation in the study area is a carbonate sedimentary system,which mainly develops a set of dolomite-dominated carbonate rocks,including stromatolite dolomite,granular dolomite,crystalline dolomite,etc.It is carbonate gently slope sedimentary facies,which can be subdivided into tidal flat and shoal subfacies and multiple microfacies.2.Reservoir rocks are mainly dolomite,including microbial dolomite,crystalline dolomite and granular dolomite,and the types of reservoir space mainly include pore type,karst cave type and fracture type.Among them,the pores can be divided into primary pores,secondary pores and microbiolite related pores in 3 subcategories and 6 subcategories,and the fractures include tectonic dissolution fractures and sutures in 2 subcategories.Pores and caverns are the main reservoir Spaces.3.From the perspective of physical characteristics,the porosity of the reservoir is generally correlated with the permeability,which belongs to the medium-porosity and low-permeability reservoir.The connectivity between the pores of the reservoir is poor,and the dissolution pores and microbiolite related pores are the main storage space,which are mainly distributed in granular dolomite and microbiolite dolomite.4.In the process of development,reservoir rocks have undergone destructive diagenesis such as compaction,compaction,cementation,filling and silicification,while recrystallization,dolomitization and dissolution are of constructive significance to the formation of reservoirs.5.The formation of the reservoir is based on the favorable sedimentary microfacies of algal shavings,intertidal algal sheets and sandy shavings,and is the result of the combined action of many factors,such as quasi-syngenetic dissolution,supergene dissolution,hydrothermal dissolution,organic acid dissolution and tectonic fracture,among which the supergene dissolution and hydrothermal dissolution have the largest impact on the reservoir.The fractures produced by tectonic fracture contribute little to reservoir space,but play a key role in improving reservoir permeability.