Study On The Carbonate Reservoir Characteristics In The Cambrian System To Lower Ordovician Series In The East Of Tarim Basin

On the basis of sign of sedimentary facies,as well as surface outcrop data,core observation,cutting logging and thin section analysis,it defined abyssal facie,bathyal-contourite drift facies , near-shore deposits and carbonate platform of sedimentary facies types , also recognized some sedimentary sub-facies and microfacies. After deeply analyzing sedimentary microfacies analyses and these dimentary model , sedimentary facies , sedimentary evolution in Early Cambrian-Middle Ordovician,we think that developing plateau-basin model in Early Cambrian,main in eastern,more obviously in Middle-Late Cambrian. Until the Early-Middle Ordovician,the sedimentary facies in the region is of typical trisection units,which are middle part deep water aulacogen sedimentary,western and eastern carbonate platform and slope facies. At the edge zone of platform and deep sea basin,there are reef flat reservoir and various diagenesis,it's good for reservoir develop.Based on the core observation and thin section analysis of seven wells on the Cambrian System to Lower Ordovician Series in the east of Tarim Basin,we found that the diagenetic process of the rocks is complex and diverse in the research area. Dolomitization,dissolution and fracturing are the main constructive diagenesis to improve the reservoir property. Cementation,pyritization,silicification,compaction and filling are the main destructive diagenesis for the reservoir. Depending on the petrologic characteristics and the tectonic setting,the dolostone,developed widely in the East of Tarim Basin,is structurally controlled hydrot??al dolomite (HTD). The fault system provided the conduit to the hydrothermal fluids. Because of the strong diagenesis,the reservoir rocks are tighter and tighter,and the porosity is low. However,the porosity of HTD is bigger than the non-HTD.There are two types of reservoirs from Cambrian to Ordovician in the east of Tarim Basin,including dolomite and limestone. The petrology,pore type,fissure and dissolved fracture types,poroperm characteristics and active porosity evolution of the types of reservoir are studied in this paper.After discussing the controlling factors of reservoir,combining with sedimentary facies distribution,diagenesis and reservoir characterization,the different types of reservoir in the eastern Tarim Basin were evaluated. Lithology,sedimentary facies,denudation and HTD are the controlling factors of reservoir. On the basis of these factors, prospective zones for oil and gas exploration were identified. They are reef and bank reservoirs along the platform margin at the west and northeast of aulacogen when the Late Cambrian and Early-Ordovician, the hydrothermal dolomite reservoirs in the Upper Cambrian.