Research On Characteristics And Controlling Factors Of Carbonate Reservoir Of Carboniferous Bachu Formation In Bashituo Oil Field

In the paper,the carbonate reservoir of Carboniferous Bachu Formation in Bashituo oil field is taken as the research object.It is based on microscopic identification,SEM observation,mercury injection test and physical parameter measurement,and combines core data,seismic data and log data.Guided by the theory of sedimentary facies and diagenesis controlling reservoir development,the reservoir is described subtly and the carbonate reservoir characteristics and main controlling factors are analyzed in detail from the aspects of lithologic characteristics,reservoir space characteristics and reservoir physical properties.The results and awareness achieved are as follows.Bachu Formation is carbonate platform sedimentary,mainly developed two subfacies,limited platform and evaporative platform,and nine microfacies.The main rock types are limestone,dolomite,transitional carbonate rock and mixed rock.The upper member of Bachu Formation is the main reservoir of Bashituo Carboniferous oil deposit,and the main types of rocks are muddy dolomite,micritic dolomite,gray dolomite and dolomitic limestone.It develops dolomite flat and lime dolomitic flat.The pores,holes and cracks are the main reservoir space types of Bachu Formation.The dolomite formation is pore type reservoir with fine throat,moderate porosity and medium permeability,and the limestone formation is crack reservoir with tiny throat,low porosity and low permeability.According to the reservoir characteristics,the reservoir of Bachu Formation is divided into three types:?₁ pore type,?₂ hole type,?crack type.The physical properties of?₁ pore type are good,?type is dominated by fractures and its physical properties are poor relatively.The reservoir development of Bachu Formation is mainly controlled by many factors.Sedimentary facies is the foundation for reservoir formation,favorable reservoir facies is concentrated in the dolomitic flat and lime dolomitic flat of restricted platform in dolomite segment.Diagenesis is the key of formation of favorable reservoir.There are eight main types of reservoir diagenesis of Bachu Formation,a large number of secondary solution pores are formed by dissolution and dolomitization,which greatly improve the physical properties of the dolomite reservoir.They are important diagenesis for the formation of reservoir in Bashituo area.The fracture caused by tectogenesis offers a good channel for the occurrence of seepage erosion and improves the physical properties,especially permeability.