Development model of compound buried-hill reservoirs in the Yingmai 32area of Tabei and its significance for exploration

A special type of buried-hill reservoirs, which is compounded by both carbonates and sandstones, has been discovered in the Yingmai 32 area of Tabei (North Tarim). This paper describes part of these reservoirs and analyzes structures and sedimentary history of the Yingmai 32 area. We suggest that the key reason for the generation of such reservoirs is that multiple-episode truncations and overlaps have happened along the unconformity surface of basement rocks. The two enormous unconformities that developed during the Middle to the Late Caledonian period and Hercynian to Indo-China period set up the foundation for the building-up of these compound reservoirs. The reservoirs could be divided into two types: truncation type and overlap type. The truncation type can be further divided into three different models: overlap, pinch-out and graben models, while the overlap type includes three sub-models: overlay, pinch-out and gully models. Such compound buried-hill reservoirs are common in Tabei. Thus we should make more efforts to describe the top surface of all connected reservoirs instead of carbonates alone, which would significantly contribute to expansion of hydrocarbon exploration.