Abstract: In Cretaceous petroleum system of Yiyang basin,the hydrocarbon source rock is grey-block mudstone of Lengshuiwu formation, which mostly contains kerogen Type I and H , higher abundance of organic matter, and belongs to a source rock of fair average quality with extensive distribution in area and medium maturity. I ate Cretaceous to present are believed to be its periods of generation, expulsion (concentrated in Yingtan sag and Guixi sag) and accumulation of hydrocarbons. The amount of resources is estimated at 0.8327x 10⁸ t~1.0899x10⁸ t. The reservoir bodies are mainly sandstones located in lower and upper Lengshuiwu formation and lower Zhoujiadian formation. The cap rocks are mudstone in middle Lengshuiwu formation and upper Zhoujiadian formation, and the latter, especially, can be as a regional cap rock. The hydrocarbon migration took place vertically and dominantly by the faults and fractures. This study showed that the two major source sags, Yingtan sag and Guixi sag will be prospecting targets for oil/ gas exploration.

Key words: Jiangxi, Cretaceous, Petroleun system, Feature, Oil and gas exploration, Evaluation