济阳坳陷青东凹陷低熟油生烃机理研究

青东凹陷勘探程度低，油气资源潜力尚未得到充分认识，开展凹陷内低熟油成因机理的研究有利于评价油气资源潜力并指导油气勘探工作。原油的物理及地球化学特征表明低熟油主要分布于凹陷边缘的沙四上亚段储层中。油源对比显示低熟油主要来自凹陷内沙四上亚段低熟烃源岩。研究区沙四段烃源岩具备形成低熟油的地质和地球化学条件：沙四段泥页岩有机质丰度高，有机质类型以腐泥型(I)和腐泥-腐殖型(II1)为主；泥页岩与蒸发岩共生的咸化还原环境因富含高矿化度地层水而有助于有机质早期转化生烃；烃源岩中的可溶有机质经过低温化学反应、细菌活动、生物催化作用等可形成低熟油。该研究对青东凹陷油气勘探工作有重要指导意义，寻找低熟油气藏是研究区未来重要的勘探方向。

Study on the Genetic Mechanism of Immature Oil from Qingdong Sag,Jiyang Depression

The source potential of Qingdong sag has not been fully recognized due to low exploration extent. Thus study on the genetic mechanism of immature oil of this sag is important for future exploration. The immature oil of Qingdong sag is mainly discovered on the edges of the sag and the source rocks are believed to be the upper submember of the 4th member of Shahejie Formation. Oil source correlation shows that immature oil are mainly from immature source rocks of upper submember of the 4th member of Shahejie Formation. On the basis of molecular geochemical and organic petrology analysis, the immature source rocks possesses geological and geochemical condition to generate immature oil, the mechanism of which are as follows: (1) the mudstone/shale of the 4th member of Shahejie Formation has high organic abundance. The organic matters types are sapropelic type(Ⅰ)and sapropelic humic type(Ⅱ1), abundant in hydrogen rich components which are prone to generate hydrocarbons in early period; (2) the symbiotic saline reducing environment of source rocks and evaporates with the strata fluids of high salinity can promote hydrocarbon generating; (3) the soluble organic matters in the source rocks are easy to generate hydrocarbon influenced by low temperature chemical reactions, bacterial activities and catalysis during the early period of evolution. Therefore, more attention should be focused on the immature oil in the future exploration of Qingdong sag.