GENETIC FEATURES OF PETROLEUM SYSTEMS IN RIFT BASINS OF EASTERN CHINA

Most oil-bearing basins in eastern China are Mesozoic-Cenozoic contine ntal rifts which have played a habitat for oil and gas in China. Inves tigation of the petroleum systems may give a better understanding of t he oil and gas habitats in these basins. Of the essential elements of the petroleum system, the source rock is the most important in rift ba sins. However, rift tectonic evolution controls all the essential elem ents and processes necessary for a petroleum system. A four stage evol ution model is suggested for the controls in the rift basin. A rift ba sin may consist of sub-basins, depressions, sub-depressions, and major , moderate, and minor uplifts. A depression or sub-depression has its own depocentre (mainly occupied by source rock) and all kinds of lacus trine sediments, and thus has all the essential elements of a petroleu m system. However, only those depressions or sub-depressions which are rich in organic matter and deeply buried to generate oil and gas form petroleum systems. Immature oil, another characteristic, complicates the petroleum system in the rift basins. Three types of oil and gas ha bitats are described as a result of this analysis of the petroleum sys tems of the 26 largest oil and gas fields discovered in eastern China rift basins: uplifts between oil source centres are the most prospecti ve areas for oil and gas accumulations, slopes connecting oil source c entres and uplifts are the second, and the third type is subtle traps in the oil source centre. (C) 1998 Elsevier Science Ltd. All rights re served.