The Research Of Sedimentary Facies And Reservoir Characteristics Of Upper Ganchaigou Formation In Zhahaquan Area,qaidam Basin

This thesis takes the deposition and reservoir characteristics of the Upper Ganchaigou Formation in the Zhahaquan area as the research object,and comprehensively uses the theory and methods of lithofacies and paleography,sedimentary petrology,and petroleum geology.The sedimentary facies,evolution and reservoir characteristics of Upper Ganchaigou Formation in this area were systematically studied.Studies suggest that the Upper Ganchaigou Formation in the Zhahaquan area is mainly a delta-lake sedimentary system,with shallow lake subfacies,semi-deep lake subfacies,braided river delta front subfacies,and gravity flow subaqueous fan deposition.The shallow lake subfacies beach bar sand body is located in the middle of the study area and is the main reservoir sand body type.Braided river delta front deposits developed in the west and southeast of the study area,and gravity flow deposits developed in deep lake subfacies.The shallow lake subfacies beach bar microfacies developed by the Upper Ganchaigou Formation in the Zhahaquan area are further divided into two subtype microfacies,the bar sand body and the beach sand body.The sand body of the bar is composed of two parts: the middle of the bar and the edge of the bar.A logging phase model of the microfacies of the bar is established.The width is finger-shaped,and the beach is finger-shaped or tooth-shaped with higher amplitude.The bars and bar edges are of high amplitude tooth shape.On the basis of sedimentary facies analysis,the deposition models of beach bar microfacies were established in the Upper Ganchaigou Formation.Through the core observation data and analysis test data,the petrologic characteristics,physical properties and sand body distribution characteristics of the Upper Ganchaigou Formation reservoir are studied.The analysis shows that the sand bodies of the Upper Ganchaigou Formation reservoir in the Zhahaquan area are mainly fine sandstone,and the rock type is mainly feldspar detrital sandstone or debris feldspar sandstone.Its structural maturity is low,its component maturity is medium to low,and its sorting performance is medium.The cementation is mainly carbonate cementation,the common form is calcite.The pores of reservoir are dominated by primary pores,and micron-sized pores are the main reservoir space.The internal structure of the reservoir is complicated.The lower sand body of the Upper Ganchaigou Formation is a tight reservoir,and the upper part is a "sweet spot" type reservoir.Reservoir formation and distribution are generally controlled by lithology,sedimentary microfacies and diagenesis.Established the dense oil reservoir classification standard in the study area,it can be divided into three categories: best I class reservoir,lithologic is fine siltstone,carbonate content is low,primary intergranular pore,dissolution pore,reservoir physical property is good.Is the present dessert distribution area.II class hierarchy of storage,mainly of fine sandstone,local carbonate cementation and clay mineral is around 10%,primary intergranular pore,dissolution pore development and physical properties of medium.? worst kind of reservoir,mainly for the powder sandstone,carbonate cementation strong,high clay content,primary intergranular pore is less,see some dissolved pore and pore,poor physical property.II classes and class ? relatively poor,low porosity,low permeability reservoir.