CONTROL OF SOURCE ROCK THERMAL EVOLUTION ON OIL AND GAS ACCUMULATION IN KUQA DEPRESSION, TARIM BASIN, NW CHINA

摘要

Investigation of representative reservoir-forming time indicates that in Kuqa petroleum system oil and gas accumulated in relatively late stage, primarily taking place since Neogene Kuche period. On the one hand, it is controlled by tectonic movement playing an important role in the formation and shaping of traps, on the other hand, it is considerably related to the rapid subsidence and accelerated thermal maturation of the Mesozoic source rocks since Paleogene. Diversity of structure effect and sedimentation in different areas results in the difference of thermal evolution history of source rocks, which controlled on plane reservoir-forming time and inhomogeneity of oil-gas distribution. The Kuqa Depression is a Mesozoic foreland basin located in the northern part of the Tarim Basin, NW China. This depression consists of three sags, Yangxia, Baicheng and Wushi from east to west. The resource evaluation shows that there are abundant oil and gas resources, which provide sufficient substance fundament of petroleum accumulation in the depression. The discovered oil and gas fields in Kuqa petroleum system are mainly distributed in the Luntai faulted uplift area and Kuqa Depression. Types of oil and gas pool are various, containing giant gas fields as well as condensate gas and oil pools. On the basis of the investigation of reservoir-forming time, oil and gas accumulated mostly in the relatively late stage. This was not only due to the period of late structure movement being mainly phase of effective trap formation in Kuqa Depression, but also attributed to thermal evolution history of hydrocarbon source rocks.