渤海湾盆地南堡凹陷西部东营组三段—沙河街组一段砂质碎屑流沉积特征及油气勘探意义

通过对岩心系统观测、岩心薄片观察和粒度分析,结合单井沉积相及地震相的综合分析,对南堡凹陷西部东营组三段—沙河街组一段沉积微相类型及特征进行精细的研究,认为研究区扇三角洲前端发育大规模的砂质碎屑流沉积。结合区域古地貌特征、沉积体系的综合研究,探讨了研究区砂质碎屑流沉积的成因机制,详细论述了砂质碎屑流的沉积构造特征及识别标志,并在此基础上建立了砂质碎屑流沉积模式。研究表明砂质碎屑流砂体主要为无沉积构造的块状中—粗砂岩和具有丰富重力流沉积特征的砂泥岩互层2种岩性组成,其成因为扇三角洲前缘砂体发生滑动、滑塌、再沉积而成。结合目前的勘探实践分析认为,砂质碎屑流砂体与沙河街组一段、沙河街组三段优质烃源岩直接接触或通过油源断层沟通而形成自生自储或下生上储型的岩性或构造-岩性油气藏,进而构成了研究区半深湖—深湖区域的良好岩性圈闭集合体。

Sedimentary characteristics of sandy debris flow in the 3rd Member of Dongying Formation and the 1st Member of Shahejie Formation of the western Nanpu sag,Bohai Bay Basin and its significance in hydrocarbon exploration

Through systematic core observation, core slice observation and grain size analysis in combination with the comprehensive analysis of single well sedimentary facies and seismic facies, a fine study was conducted on the types and characteristics of sedimentary microfacies of the 3rd Member of Dongying Formation(Ed₃) and the 1st Member of Shahejie Formation(Es₁) in the western Nanpu sag. It is believed that in the study area, large-scale sandy debris flow deposition is formed in the front of fan delta. Based on comprehensively studying the regional ancient landform characteristics and sedimentary system, this paper further explores the formation mechanism of sandy debris flow deposition in the area and the sedimentary structural characteristics, and also detailedly sandy debris flow deposition in the area and the sedimentary structural characteristics, and also detailedly describes the identification marks of sandy debris flow. On this basis, the sedimentary model of sandy debris flows was established in this study. Research shows that sandy debris flow sand bodies are mainly composed of massive medium-coarse sandstones without sedimentary structure and the sand-shale interbed characterized with abundant gravity flow depositions, which are formed by slump, slip and redeposition of sand body in the fan delta front. According to the current exploration practice and analysis, it is believed that sandy debris flow sand body can directly contact with high-quality source rocks in the 1st Member of Shahejie Formation and the 3rd Member of Shahejie Formation(Es₃) or communicate with the source rocks through source fault, and form self-generation and self-preservation or lower-generating and upper-reservoiring lithologic or structural-lithologic reservoir, and thus constitute an aggregation of favorable lithologic traps in semi-deep-deep lakes of the study area.