南黄海盆地南部坳陷中-新生界沉积体系研究——以南五凹陷为例

The Meso-Cenozoic sedimentary system in the southern depression of the South Yellow Sea Basin: A case study of the Nanwu Sag

  • 摘要: 南黄海盆地南部地质结构复杂,勘探层系多,资源潜力大,但目前对于该盆地海域部分的勘探程度仍然较低,尤其是针对南部坳陷带中-新生界陆相沉积的地层沉积特征及源汇体系尚未开展系统的研究,对于中部隆起区的物源是否能长距离向南部坳陷带搬运存在一定争议,制约了寻找有利储集相带的勘探。本文以盆地南部坳陷南五凹陷为例,类比周边各凹陷,通过二维、三维地震资料精细解释及新、老钻井岩电特性、岩芯相对比,对南黄海盆地南部坳陷中-新生界重点层系沉积类型及特征进行识别,划分出该区物源、输送通道及汇聚区域,建立一套针对南五凹陷的沉积模式,从而构建合理的沉积相时空配置关系。结果表明中-新生代南部坳陷南五、南七与南二凹陷的沉积地层特征存在一定差异,南五凹陷水体具有浅-深-浅-深的变化规律;凹陷南部陡坡带沉积相带以短轴物源为主,主要发育湖泊-冲积扇-扇三角洲沉积体系,物源方向主要来自南部勿南沙隆起;而北部缓坡带则以滨浅湖-辫状河三角洲前缘沉积环境为主,物源主要来自于南黄海盆地中部隆起区的西部,少部分来自于南二凸起。

     

    Abstract: Abstracts: The southern part of the South Yellow Sea Basin has complex geological structures, many exploration layers, and great resource potential. However, the current level of exploration in the sea area of the basin is still low; especially the sedimentary characteristics and source-sink systems of the Mesozoic and Cenozoic continental deposits in the southern depression belt have not been systematically studied, and whether the sources in the central uplift area can be transported to the southern depression belt over long distances remains controversial, which has more or less restricted the exploration work to find favorable reservoir facies zones. We took the Nanwu Sag in the southern depression of the basin as an example, compared and analyzed the surrounding depressions, used fine interpretation of two-dimensional and three-dimensional seismic data, as well as compared new and old drilling rock electrical characteristics and core samples, based on which the sedimentary types and characteristics of the Meso-Cenozoic key strata in the southern depression of the South Yellow Sea Basin were identified, and the provenance, transport channels, and convergence areas of the basin were divided. Meanwhile, a set of sedimentary models for the Nanwu Sag was formed, and a reasonable temporal and spatial configuration relationship of sedimentary facies was established. Results show that during the Mesozoic and Cenozoic eras, water body in Nanwu Sag experienced from shallow to deep, then to shallow, and to deep water again. The sedimentary facies belt in the steep slope zone in the southern part of the depression is dominated by materials from short-axis sources, of which a semi-lacustrine-alluvial fan-fan delta sedimentary system was developed, and the materials came from the southern Bunansha uplift, while the northern gentle slope zone is dominated by materials from a shallow lake-braided river delta front, and the source mainly came from the west of the central uplift area of the South Yellow Sea Basin, and a some from the Nan’er Uplift.

     

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