冀中饶阳凹陷蠡县斜坡古近系沙河街组沙二段及沙一段下亚段沉积相与隐蔽油藏

蠡县斜坡是冀中饶阳凹陷西部的一个大型宽缓斜坡，以倾向上的小坡降和走向上的古地形差异相对较显著为特征，自北而南呈现出台地区和单斜区等不同的地貌单元。区内古近系沙河街组沙二段和沙一段下亚段发育“浅水型”三角洲和滨浅湖滩坝两种沉积相类型，构成了斜坡带的主要储集体。根据斜坡带走向上的古地貌、沉积相类型等基本因素的差异，可归纳为两种类型的砂体发育区：1）斜坡南段单斜区的三角洲相砂体发育区和2）斜坡北段台地区的滩坝相砂体发育区。通过隐蔽油藏勘探方向分析，认为这两种不同类型砂体发育区的隐蔽油藏形成条件各异。以台地区的滩坝相砂体发育区最为有利，是隐蔽油藏勘探的主要方向。在斜坡的内带、中带和外带等不同部位，隐蔽油藏成藏模式也各不相同，以斜坡中带的隐蔽油藏类型发育最为齐全，是寻找规模储量的主要靶区。

Sedimentary facies and subtle petroleum reservoir of the Member 2 and lower submember of Member 1 of Shahejie Formation of Paleogene on Lixian Slope of Raoyang Sag, Central Hebei Province

Lixian Slope is a large wide-gentle slope in the western part of Raoyang Sag, Jizhong Depression, Bohai Bay Basin. It is characterized by low gradient in the tendency and relatively obvious palaeotopographic differences in the trend, and it is constituted of different terrain units such as platform and monocline areas from north to south. Based on observation of cores and analysis on individual well facies and logging facies, and combining with numerous test data such as granularity, petrology and mineral analyses, etc, two different sedimentary facies, including “shallow water” delta, sand bar and beach of shallow-shore lacustrine, are recognised, which constituted the main reservoir of the Member 2 and the Lower part of Member 1 of Shahejie Formation of Paleogene in the study area. According to the differences of basic elements including sedimentary facies types and palaeogeomorphology in the trend, two different types of sandbody concentrating areas are classified in the study area, respectively named as delta facies sandbody concentrating area of monocline slope terrain unit and sand bar and beach facies sandbody concentrating area of platform terrain unit from south to north of the Lixian Slope. However, the forming conditions of subtle petroleum reservoir are different. It is suggested that the concentrating areas of sand bar and beach facies sandbodies of platform terrain unit are the favorable areas for searching subtle petroleum reservoir. Whereas compared to the sand bar and beach facies sandbody concentrating area of platform terrain unit, the exploration potential of the delta facies sandbody concentrating area of monocline slope terrain unit is relatively poor. On the other hand, the models of subtle petroleum reservoir are different on the inner, middle and upper belts of Lixian Slope. In general, the middle belt of the slope distributes a variety types of subtle petroleum reservoir which consist of sandstone updip pinch-out, lenticle lithologic oil reservoir and structural-lithologic oil reservoir. Vertically and laterally, these types of subtle petroleum reservoir overlaped each other and their oil-bearing beds were widespread on the middle belt of the slope, so the middle belt of the slop is considered as a main target area for subtle petroleum reservoir exploration.