车镇凹陷车西洼陷油气倒灌运移成藏特征及机理

针对车镇凹陷车西洼陷是否存在油气倒灌运移成藏这一问题,从基本地质特征分析入手,对油源对比、有效烃源岩展布特征、烃源岩与储层对接关系进行了研究。结果表明,沙三段烃源岩是车西洼陷的有效烃源岩,沙四段上亚段油藏为"上生下储"型,沙三段4700m以下有效烃源岩存在油气倒灌成藏现象。源储对接关系分析表明,曹家庄断阶带以北洼陷区沙四段上亚段油藏中的原油来自上部沙三段烃源岩。油气成藏要素剖析结果表明,沙三段与沙四段上亚段"厚泥下砂"的岩性匹配关系、沙三段烃源岩超压、烃源岩与储层之间的压差以及隐蔽输导体系是油气倒灌运移成藏的主控因素;油气倒灌运移距离与烃源岩剩余压力具有正相关关系,烃源岩之下储层的物性条件对其含油性具有控制作用。

Mechanism and characteristics of petroleum downward migration in Chexi sag of Chezhen depression

In response to the phenomenon of petroleum downward migration exist in Chexi sag of Chezhen depression, herein, beginning from the analysis of the basic geological characteristics and combined with the oil-source correlation, and the distribution of effective source rock, and the position of the source rock and reservoir, the research showed that there does exist the phenomenon of petroleum downward migration below the burried depth of 4 700 m under the effective source rock of the third member of Shahejie formation(Es3) in this area. By means of oil-source correlation, it is confirmed that the oil in the pools of the fourth member of Shahejie formation(upper Es4)layer in the north of Caojiazhuan fault terrace in the sag is from the upper layer, the Es3 effective source rock in this area. On the basis of analysis of reservoir formation factors, it is clear that there are four main factors which control the reservoir formation by the downward migration. These main factors are the lithological relationship between sandstone in upper Es4 layer and the thick mudstone in the upper Es3 layer , the overpressure of the effective Es3 source rock, subtle passage system and the pressure difference between the reservoir and effective source rock. There is a positive correlation between the distance of petroleum downward migration and residual pressure in the effective source rock. The oil saturation was controlled by the physical characteristics of the reservoir under the source rock. The viewpoint above further improves the theoretical understanding on the reservoir formation in Jiyang depression and can be used as reference for exploration practice in Bohaiwan basin.