ACCUMULATION CHARACTERISTICS AND PETROLEUM DISTRIBUTION IN JIUFOTANG FORMATION, THE LUXI SAG, THE KAILU BASIN

The Luxi Sag in the Kailu Basin is a Meso-Cenozoic faulted basin with high quality source rock in which kerogen belongs to type Ⅰ-Ⅱ and the source rock has entered low maturity-maturity stages for oil generation.Source rock quality of the lower member of Jiufotang Formation is better than that of the upper member.Oil generation and discharge took place during Yanshanian epoch and Late Cretaceous.The main centers for oil generation locate in Wushijiazimiao as well as Xiaojingzi.Oil accumulation mainly occurred during Fuxin stage.Sandbody distribution of delta,nearshore subaqueous fan is controlled by fault activities.These sandbodies develop primary porosity and are characterized by high-medium porosity and low permeability when buried over 1 600 m deep.The mudstone of Shahai and Fuxin Formations works as regional cap.The mudstone of Jiufotang Formation is local cap.The Majiapu uplift,Baoriwendu fault belt and Mabei slope are close to source center,and are the areas for oil migration trend.The oil formation in lithologic-structural trap and lithologic trap is controlled by the organic combination of sandbodies and faults.The authors predict that the favorable regions for oil exploration locate in the northern Majiapu uplift and the middle Baoriwendu fault belt.