Main Thrust Fault Controlling on Hydrocarbon Accumulation in Wuxia Thrust Belt, NW Junggar Basin: Evidences from Paleo-fluid Data
Fang, Shihu; Zhao, Mengjun; Cao, Hongliang; Liu, Shaobo
The Wuxia thrust belt is a hydrocarbon rich structural zone in the NW Junggar basin, with several giant oil & gas discoveries in recent years, such as the Fengcheng1, Wu35, Xia72 and so on. But the divergences were always existed on source rock, timing of hydrocarbon accumulation and the relationship between the reservoirs in hanging wall and footwall. To resolve these problems, many well cores samples from hanging wall and footwall were collected to study the fluid inclusion and reservoir bitumen. By comprehensive analyses on infrared spectrum, laser raman spectroscopy and confocal laser measure gas-liquid ratio of fluid inclusion, and quantitative grain fluorescence, organic geochemistry analysis of reservoir bitumen, the main fault controlling on different charging history in the hanging wall and footwall was analysed. Combined with the history of hydrocarbon generation of source rocks and structural evolution history, all data indicated that the oil and gas reservoir in hanging wall are mainly formed in one period, related to the late Triassic charging and the maturity of crude oil is relatively low. Whereas, the two stage of oil and gas charging in footwall are mainly in the late Triassic and late Jurassic-early Cretaceous, and the latter is the main charging phase for present oil and gas reservoir. The main fault has a transportation effect in the process of oil and gas migration during the late Triassic charging, and then the main fault acted as blocked seal for hydrocarbon migration during the later oil and gas charging period. The main fault evolution and its control on hydrocarbon accumulation led to the differences in oil and gas charging and distribution between the hanging wall and footwall.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013