洞庭盆地沅江凹陷的构造演化特征与含油气性分析

【作者】 戴传瑞；

【导师】 张廷山；

【作者基本信息】 西南石油大学 ， 矿产普查与勘探， 2006， 硕士

【摘要】 沅江凹陷位居洞庭盆地之中，是其中的一个沉陷最深、地层发育最完整、沉积厚度最大、油气显示最丰富、资源前景最好的凹陷。该凹陷北与华容隆起相接，南邻雪峰隆起，东西分别与麻河口凸起和目平湖凸起相连，呈北东向延伸，长约75千米，宽约33千米，是一个较典型的东南断西北超的中、新生代箕形凹陷。论文总的指导思想是以“盆山耦合”理论、石油与天然气的有机成因论、含油气系统等现代石油地质理论为基础，以整体、动态、系统、综合分析为原则，以成盆-成烃-成藏研究为主线，从盆山耦合关系切入，研究含油气系统成藏要素及其相互作用过程，探讨油气成藏主控因素和油气分布的有序性，取得如下主要的创新性成果和认识： （1）系统分析了洞庭盆地形成演化与雪峰—幕阜构造带的关系，提出来了盆山之间一共经历了四期的盆山耦合过程：1)燕山早中期的盆山耦合过程；2)燕山晚期的盆山耦合；3)早喜马拉雅期的盆山耦合：4)晚第三纪的盆山耦合。 （2）描述了沅江凹陷内的构造样式，认为凹陷内构造变形具有西南断、东北超的的箕状断陷特征，凹陷划分为三个一级构造带及九个二级构造带，并将其在各个盆山耦合过程中的具体构造演化特征划分为5个阶段：①中白垩世扭张性盆地发展阶段，②晚白垩世坳陷阶段，③古新世至始新世断陷盆地扩张阶段，④始新世中晚期断陷盆地收缩阶段，⑤晚第三纪至第四纪坳陷阶段等五个阶段。 （3）结合本区的烃源岩演化史，对本区油气运聚成藏关键性的构造运动有三期：①侏罗纪末—白垩纪早中期的晚燕山运动②早第三纪的早喜马拉雅运动早期③晚第三纪—第四纪的喜马拉雅运动晚期。 （4）从该区现有典型油气分布特征着手，总结出影响该区油气分布的主要因素：①深凹陷生油；②断裂控油；③不整合面控油；④裂缝系统控油等。 （5）沅江凹陷下第三系和白垩系油源均来自下第三系本身，在对其含油气系统的划分上，将其作为“一源多储”的三个相互叠置的含油气系统对待：1)E₁t+E₂y¹-E₂y含油气系统；2)E₁t+E₂y¹-K₃f含油气系统；3)E₁t+E₂y¹-E₂h含油气系统。上述三个含油气系统虽然储集层各不相同，但是烃源层基本上是一样的。因此，最终构成了“一源多储”的复合系统。从勘探角度来看，目前的研究对象主要集中在前两个含油气系统。 （6）我们综合认为沅江凹陷的有利烃源层主要发育在半地堑的二个深洼部位，早第三纪沅江早期，是凹陷的主力烃源岩主要发育期，控制了烃源岩的分布、规模和质量。因而紧靠深凹生烃中心的东次凹净下洲深洼断块断背带和三洲咀断鼻带，具有较得天独厚的烃源供给条件，又发育有较好的白云岩、砂岩储集岩，生储层系的空间配置好，油气输导条件优越，具有沅江组烃源岩生烃高峰期或前的断块、断鼻、断背构造圈闭，及砂岩岩性圈闭，是有利的油气聚集成藏区带。但由于晚喜山更多还原

【Abstract】 The further review of source in Yuanjian depression which located in Dongting basin is best for Its most deep of sunken and the most perfectly development of stratum and the most thickness of sediment and the most abundance of petroliferous of characters . It is conterminous of the Huarong arch in the north and adjacent of Xuefeng mountain in the south, and in the east and west of the depression are Mahekou arch and Mupinghu arch, and it is extend to along the direction of North-East, and its length is about 75Km2 while the width is almost 33 Km~2,and On describing the structural style of Yuangjiang depression, we hold the opinion that the representative characteristic of transmogrification is subsidence of fault blocks as a dustpan which the southwest of depression has take on the shape of rupture while the bestow of northeast. In this study , based on the main theories such as Plate tectonics, Basin-mountion coupling development, organic origin of petroleum, sequence stratigraphy ,petroleum system and the main analysis principle of entirely , dynamic, system , synthesis; along the main way of basin - source -petroliferous pool, we main analyzing the yuanjiang depression and its adjacent regional characteristic of tectonic evolvement entirely; summarizing the relation of its tectonic evolvement and the distributing of oil-gas; summarizing the distributing disciplinarian of gas- oil. The following are main conclusions included:(1)The style of the structure、 the feature of the tansmutation and formation between Dongting basin and Xuefeng-Mufu Orogenic belt are Synthetical analyzed,we consider that there is extreme coupling between the Orogenic belt and basins in the diffirent periods of meso-Cenozoic: 1) The early and metaphase stage of Yansha (J3—K1 -2); 2) The late stage of Yanshan (K31-2); 3) The early stage of Himalayan movement (the late stage of the late Cretaceous to the Paleogene); 4) The late stage of Himalayan movement (Neogene-Quaternary) .(2)On describing the structural style of Yuangjiang depression, we hole the opinion that the representative characteristic of transmogrification is subsidence of fault blocks as a dustpan which the southwest of depression has take on the shape of rupture while the bestow of northeast.we can despart it into three main tectonic unites and nine secondary tectonic unites, and in the course of each Basin-mountion coupling development, Yuanjiang depression has experienced such phase: ①The formation of so-shear rift basin in the stage of middle Cretaceous②The formation of subsidence basin in the stage of late Cretaceous③in the stage of subsidence of fault blocks overspread between Paleocene and Oligocene.④In the middle-late stage of subsidence of fault blocks shrink in late Oligocene⑤In the stage of subsidence in the Neogene-Quaternary.(3)Combining the history of evolvement of source in this study area, we hold the opinion that there are three most crucial structure movements as the follows: ①The early and metaphase stage of Yansha (the late stage of the Jurassic to the The early and更多还原