开鲁盆地陆西凹陷九佛堂组油气成藏特征及分布

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

开鲁盆地陆西凹陷属中、新生代断陷盆地,其中九佛堂组发育烃源岩,有机质丰度高,干酪根类型以Ⅱ—Ⅰ型为主,九佛堂组下段烃源岩质量优于上段,均已进入低成熟—成熟阶段。生、排烃主要发生在燕山期—晚白垩世早期,五十家子庙洼陷是最重要的生烃洼陷,小井子洼陷次之。阜新期为主要的油气聚集期。受断裂活动和分布控制的三角洲、近岸水下扇等多种类型的砂体原生孔隙发育,埋深1 600 m以上的砂体具高—中孔隙度和低—超低渗透率储层物性。沙海组和阜新组的泥岩层是九佛堂组油气藏的区域盖层,九佛堂组的泥岩层可作局部盖层。马家铺高垒带、包日温都断裂带和马北斜坡带与生油洼陷相间,具有良好的生、储配置关系,是油气运移和聚集的指向场所。油气通过断层与砂体共同构成的输导体系运移、聚集至有利的岩性—构造圈闭和岩性圈闭中成藏,预测马家铺高垒带北部和包日温都断裂带中段为最有利的油气勘探区域。

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.