中国东部中、新生代陆相断陷盆地沉积充填模式及其控制因素——以济阳坳陷东营凹陷为例

Depositional filling models and controlling factors on Mesozoic and Cenozoic fault basins of terrestrial facies in eastern China——A case study of Dongying Sag of Jiyang Depression

中国已发现的油气储量大多来源于中、新生代陆相断陷盆地,这些盆地大小各异、类型众多,储量相差悬殊,但大多已发现并开发的油田为明显的构造圈闭。随着我国油气勘探的不断进行及难度的增加与转型,当前油气勘探的目标已转移到隐蔽岩性地层圈闭中,因而很有必要对这些断陷盆地不同区带和各演化阶段的沉积充填特征进行认真分析和研究,以便为进一步的岩性地层圈闭勘探提供地质理论与科学依据。东营凹陷隶属于渤海湾盆地济阳坳陷,是一个典型的以陆源粗碎屑沉积为主的断陷湖盆,其沉积充填型式和砂体展布特征都具有代表性。因此,该文将着重在空间和时间2个方面从沉积学角度对东营凹陷进行剖析,阐述构造特征直接控制沉积充填特征、气候主要控制沉积物性质、沉积物补偿和湖平面升降主要控制沉积充填的空间展布型式这样一组对应关系,最后总结出不同构造区带各演化时期沉积充填模式及其对比关系,为丰富陆相断陷湖盆中油气生成和分布规律提供帮助与依据。

A majority of oil and gas reserves have been discovered that are located in the Mesozoic and Cenozoic fault basins of terrestrial facies in eastern China. These basins have different sizes and types with great discrepancy of reserves, whereas most of oil and gas fields that have been discovered and developed are obvious structural trap. With the continual enhancement of Chinese hydrocarbon exploration activity, the difficult increasing and type transferring, the targets of hydrocarbon exploration have been changed to subtle lithologic and stratigraphic trap. Therefore it is much necessary to analyze and research the characteristics of depositional filli ng at different structural zone during different evolutive phrases in this basin in order to provide geological theories and science evidences for the exploration of lithologic and stratigraphic trap. Dongying Sag belongs to Jiyang Depression of Bohaiwan Basin, which is a typical lake basin of half-garben with the terrestrial coarse clastic deposits. The depositional filling pattern and extensional characteristic of sandstone within Dongying Sag are very representative to study this type of basin. So, the paper emphasized that Dongying Sag has been analyzed from both spatiality and time in the view of sedimentology. A set of corresponding relationship has been expatiated that structural characteristic directly controls the depositional filling characteristics, climate straightly determines the property of deposits, sediment supply and lake-level changes mainly dominate the patterns of spatial depositional filling. The depositional filling model and corresponding relationship in the various structural zones during each evolutive stage have finally been summed up. These results can provide help and evidences for hydrocarbon generation and distribution in fault basin of terrestrial facies.