Accumulation conditions and play targets of oil and gas in the Cambrian subsalt dolomite, Tarim Basin, NW China

Abstract

Based on seismic, well drilling and crop data in the Tarim Basin, the accumulation conditions including source rock, reservoir, caprock and paleouplift of the Cambrian subsalt dolomites have been investigated, and favorable exploration areas have been selected. The research results reveal: there are two sets of source rock, the excellent Cambrian Yuertusi Formation source rock and the potential Nanhua-Sinian source rock, in the Tarim Basin. The dolomite reservoir of platform mound-shoal and platform margin reef-shoal facies is extensive in the Lower Cambrian Xiaoerbulake Formation in Taixi terrace area. The Middle Cambrian high quality gypsum-salt caprock has an area of about 11×104 km2; three inherited paleouplifts control the distribution of reservoirs and development of lithology stratigraphic traps and hydrocarbon accumulation, therefore, there are very good geologic conditions for the formation of large oil and gas fields in the Tarim Basin. Five oil and gas plays, namely, Tazhong-Badong intra-platform shoal, Tabei platform margin-reef bank, Keping platform margin-reef bank, Yulong-Moyu evaporative dolomite flat and Lunnan-Gucheng platform margin have been picked out, which provides a scientific basis for the oil and gas exploration and development in the Lower Cambrian dolomite. Key words: Tarim Basin, Cambrian, dolomite, hydrocarbon accumulation, play, rift trough, fault break belt, double-bank depositional model, paleouplift