Tectonic-fluid Environment Of Deep Ordovician Reservoir Development In Tabei Area,Tarim Basin

Through core slice,imaging logging,conventional logging,seismic data,isotope geochemistry,fluid inclusion data and production testing,this paper studies reservoir characteristics,tectonic background and fluid environment of the Ordovician Yijianfang Formation karst reservoir in Halahatang area of Tabei Uplift.The following understandings are obtained.(1)The Yijianfang Formation karst reservoir is mainly a low-porosity and low-permeability granular limestone reservoir that was developed in open platform reef-shoal facies;the reservoir space of the Yijianfang Formation is classified into four types: dissolution pore,dissolution pore,karst caves and structural fractures;the karst reservoirs of the Yijianfang Formation are divided into porous reservoirs,fracture-cave reservoirs,fractured reservoirs and cave reservoirs.(2)The faults in the study area can be divided into three grades,which are classified into three formation stages,i.e.the middle Caledonian stage,the early Hercynian stage and the late Hercynian stage;the fractures developed in the study area are divided into structural fracture and diagenetic fracture,and their formation ordert is non-directional fracture,low-angle fracture,suture line,high-angle fracture and near-vertical fracture.(3)The fluid environment of the Yijianfang Formation karst reservoirs can be divided into three types: marine environment,atmospheric freshwater environment and deep burial environment,and can be also divided into four stages in terms of formation time,i.e.(quasi)contemporaneous atmospheric freshwater fluids,mid-Caledonian atmospheric freshwater fluids,late Caledonian-early Hercynian atmospheric freshwater fluids and late Hercynian deep hydrothermal fluids,and the models of fluid interactions in these stages are established.(4)According to reservoir distribution characteristics,fracture characuteristics,fluid action patterns and single well karst reservoir models of different types of reservoirs,a structural-fluid geological model for the development of the Ordovician Yijianfang Formation karst reservoirs in Halahatang area is established.