Abstract: The main factors controlling the development of carbonate karst reservoir of the Yingshan Formation, Tarim Basin Central Uplift are discussed here to provide a theoretical basis for exploring lithological hydrocarbon reservoir traps of the Yingshan Formation. Results of rock core and thin section observation and physical data analysis, along with borehole imaging interpretation suggest that the carbonate rocks of the Yingshan Formation form a low-porosity, low-permeability karst reservoir. The reservoir space mainly comprises dissolution pores, fractures, and dissolution cavities. The mid-lower Ordovician carbonate reservoir is classified into several types such as fracture-pore, fracture, dissolution pore, and karst cavity. The development process of the karst reservoir is described in detail, and the factors controlling the development are also discussed:(1) mid-Caledonian phase I led to the uplift of rock layers and formation of a broad anticline structure. Carbonate rocks generally experienced leaching and corrosion parallel to the strata. Extrusion fold and faulting from tectonic activities formed numerous structural fractures, resulting in increased vertical permeability and horizontal connectivity of the limestone strata; (2) micritic limestone, dolomite-containing limestone, and dolomitic limestone are more compact lithologically, and only corroded along fractures to form dissolution pores-expanded dissolution cracks during the karst process. Limestone-containing dolomite and calcite dolomite have good porosity and permeability, and a section of the underlying dolomite strata is exposed to the surface. This enabled surface water to easily flow through dolomite strata, thereby forming a large number of pores; (3) dolomitization in general enhances the porosity and permeability of the dolomite strata (due to favorable structure and high dolomite content), providing the basis for the karst process.

Key words: Tazhong Uplift, Yingshan Formation, karst reservoirs, dissolution pores, dolomitization