东营凹陷沙四段滩坝砂微相划分与砂体横向预测——以王家岗油田王73井区为例

在东营凹陷王73井区的沙四段地层中,发育有典型的湖相滩坝砂体沉积。根据岩心特征、滩坝单砂体的平面展布、平面单砂体不同位置的垂向粒度变化,将本区沙四段与滩坝有关的沉积微相划分为滩坝主体、滩坝后缘、滩坝前缘、坝后湖湾、滨湖沉积等。研究区沙四段的滨浅湖沉积在垂向上发育较为对称的高频基准面上升半旋回和下降半旋回。这些滩坝砂体主要沉积在湖平面由上升转为下降的相对稳定期,可根据滩坝后缘与滩坝前缘的垂向沉积序列和组合来判断滩坝主体的分布位置。

Microfacies classification of shoal-bar sand and lateral prediction of sandbodies of the fourth member of Shahejie formation in Dongying depression

In the fourth member of Shahejie formation of Wang 73 well field in Dongying depression,typical lacustrine shoal-bar sand bodies are developed.According to core characteristics,plane distribution of single shoal-bar sand body,and plane vertical grain variation of single sand body at different positions,the microfacies related with shoal-bar can be divided into main body,frontier, rear,bend behind bar,ripicolous deposits,etc.Vertical- ly,the shore-shallow lacustrine sediments of the fourth member of Shahejie formation in the study area are devel- oped into symmetrical high-frequency semi-ascending cycle and semi-descending cycle.These shoal-bar sand bodies mainly deposited at the relative steady period of the surface of lake from ascending to descending.Therefore, the distribution position of shoal-bar body can be deter- mined by vertical sedimentary sequence and assemblage of bar front and rear.