PETROLEUM GEOLOGIC CONDITIONS AND EXPLORATION PROSPECTS OF CARBONIFEROUS IN THE EAST OF QAIDAM BASIN

Based on organic geochemistry analysis of source rocks,combined with regional geologic survey and seismic data interpretation,it is discussed in this paper geologic conditions and exploration prospects of Carboniferous in the east of Qaidam Basin.Carboniferous is widely distributed in the region with large residual thickness.There are many categories of hydrocarbon source rocks.Dark-colored mudstones belong to good source rocks with 1.85% of organic carbon,type-Ⅱ₂ and Ⅲ organic matters and moderate maturity.And carbonates belong to moderate source rocks with 0.42% of organic carbon,type-Ⅱ organic matters and moderate maturity.All source rocks are in the peak period of oil generation and expulsion and have strong hydrocarbon generation ability,except for those in the Zongwulong mountain front belt and the Dulan area,where thermal evolution degree is too high.With moderate-good source rocks,several reservoir beds and capping formations as well as good trap conditions,Carboniferous in the east of Qaidam Basin has experienced the process of hydrocarbon generation,migration and accumulation,hence is favorable for petroleum exploration.The Delingha Depression is most favorable for hydrocarbon generation with good Carboniferous source rocks and large residual thickness.The Zongwulong mountain front structural belt and the Tuonan fault terrace belt are prospective areas.