Sedimentary And Reservoir Characteristics Of The Cambrian Pre-salt Dolomite In The Northwestern Tarim Basin

The paper focuses on the pre-salt dolomite of the Cambrian Xiaoerbulak Formation in Keping,Bachu,Tazhong and Tabei areas of the Tarim Basin.Based on the theory of carbonate sedimentary petrology,structural geology,petroleum geology and reservoir geology,this paper makes full use of existing data to study the petrological characteristics,sedimentary facies division,sedimentary facies distribution and sedimentary model,reservoir space type,reservoir performance evaluation and reservoir distribution characteristics of the Xiaoerbulak Formation dolomite in the study area,combined with a series of analysis means such as field outcrops and core observation,section identification,scanning electron microscopy and so on.The Xiaoerbulak Formation in the study area mainly consists of four sedimentary facies,namely the restricted platform,the open platform,the platform margin and the platform slope.The Xiaoerbulak Formation in the Bachu area and the Keping area is relatively complete.The restricted platform of the study area is mainly distributed in the Bachu area.The tidal flat,the lagoon and intraplatform microfacies can be identified,and the tidal flats develop microfacies such as Yunping,Muyunping and Cream Yunping,and the lagoon develops microfacies such as Muyunping,Yunping and Salt rock.The southern part of Bachu and the northern part of the tower are mainly algal Yunping microfacies.The northern depression is consisted of the open platform phase,the central area is Inland.The periphery of the northern depression is intraplatform microfacies.Tashen 1 well and the Sugetabak section in Keping area is the platform margin zone.The platform slope phase mainly includes the Xinghuo 1 well as a typical drilling well.The reservoir space of the Xiaoerbulak Formation in the study area is mainly composed of intercrystalline pore and corroded pore,intergranular pores and Grain of die,algae lattice hole,dissolution pore and fractures.The main reservoir space combination is pores and holes.The main reservoir types are type ? and type ?.Xiaoerbulak Formation reservoir in study area is mainly affected by sedimentary facies,diagenesis,tectonic action.A high-quality reservoir with stable thickness is developed at the top of Keping area and Bachu area.The lower reservoir is heterogeneous,the reservoir thickness is thinned and the reservoir quality is deteriorated.The thickness of the reservoir in the Tazhong area is thinner and the reservoir quality is general;the reservoir in the Tabei area is not developed.