Distribution of Overpressure Zones in Deep Sub-Sag Area in Hinterland of Junggar Basin

The drilling data and the history of organic matter thermal evolution and overpressure evolution show that the deep sub-sag in hinterland of Junggar basin area is characterized by overpressure caused by thermal pressurization of hydrocarbon generation and the fluid transmission communicating with the deep overpressure system. And its top interface of overpressure is closely related to the hydrocarbon accumulation. Application of the distribution of stratigraphic overpressure to guidance of oil-gas exploration has been confirmed by the drilling information,providing a new method for strengthening the exploration in this area. The overpressure fluid in this deep sub-sag area flows toward the top interface of high-pressure compartment followed by breakthrough and accumulation,which may occur in range from 200 m obove the top interface and 100 m below it as a favorable interval for hydrocarbon accumulation. The outside of the compartment is favorable for crude oil accumulation and the inside of it for natural gas accumulation.