Karst System and Reservoir Characteristics of Yingmai-32 Buried-Hill Area in Western Tabei Uplift,Tarim Basin

Based on systemic study of karst development mechanism of Yingmai-32 buried-hill area in western Tabei uplift, the karst development model is developed, which can be divided into two cycles in vertical, including five superficial karst belts such as upper flow belt, upper groundwater flow belt, lower flow belt, lower groundwater flow belt and the deep tranquil flow belt. The superficial karst belt has a mean thickness about 24.5 m above the dolomite buried-hill area, but it becomes thinner in the limestone buried-hill area. Horizontally, the most developmental region of superficial karst belt is distributed along the top area of the Upper Cambrian dolomite buried-hill, controlled by lithofacies belt and ancient relief. It is concluded that the karst system is intimately related with the buried-hill reservoir. The distributed configuration of top buried hill reservoir is controlled by the assemblage of mudstone cap rock of Cretaceous Kapushaliang group, the superficial karst belt and the upper flow belt. Under the condition of cutting off by the relative tight upper flow belt, oil and gas migrate mainly along the netty crack-cavity system in the superficial karst belt. In the process of migration, they accumulate into the paleohigh of the buried-hill and form a karst quasi-layered reservoir.