东营凹陷西部沙河街组三段下亚段泥页岩沉积微相

关于沉积微相,前人多针对粗碎屑骨架砂体沉积相开展研究工作,对泥页岩这种细粒沉积物的沉积微相很少关注。在一个沉积盆地中,细粒沉积物的总量巨大,在纵向上及平面上均广泛分布。以东菅凹陷西部沙河街组三段下亚段(简称沙三下亚段)泥页岩为研究对象,系统划分泥页岩岩相类型。在骨架沉积相控制下,以泥页岩岩石类型及岩相特征为基础,综合控制泥页岩发育的水动力条件、古湖盆底形及事件沉积等因素,将东营凹陷西部沙三下亚段半深湖、深湖相进一步划分为平阔半深湖微相、水下隆起半深湖微相、深洼微相、浊积周缘微相、近岸水下扇前缘微相等。分析了不同微相在矿物组成、岩石类型及组构、成岩作用及测井曲线响应等方面的差异性,细粒沉积物微相的划分和研究对于泥页岩油气的勘探开发工作有重要指导作用。

Characterization of sedimentary microfacies of shale in the lower third sub-member of Shahejie Formation,western Dongying sag

Previous studies on sedimentary microfacies are mainly focused on coarse clastic skeleton sand bodies, whereas less attention has been paid to shale-related fine-grained microfacies. This is despite that huge amounts of fine-grained deposits are widely distributed in sedimentary basins in both horizontal and vertical planes. This paper takes the example of shale lithofacies in the lower third sub-member of Shahejie Formation (Es₃^x), western Dongying sag for systematical classification of shale facies. Under the control of skeletal sand bodies, the semi-deep and deep lacustrine facies of Es₃^x is divided into five types of microfacies based on shale rock types and lithofacies characteristics, combined with the control of factors such as hydrodynamic conditions for shale development, palaeogeomorphologic features, and sedimentary events. These types include flat-broad semi-deep lacustrine microfacies, submerged uplift semi-deep lacustrine microfacies, deep depression microfacies, turbidite outer edge microfacies, and subaqueous fan front microfacies. Further, the differences in mineral composition, diagenesis, and log response among different microfacies are analyzed. The study on sedimentary microfacies of fine-grained deposits is of guidance value especially for oil and gas exploration in shale reservoirs.