东营凹陷正理庄地区沙一段石灰岩沉积相

Sedimentary Facies of Limestone of Sand Layer-1 in Zhenglizhuang Area,Dongying Sag

东营凹陷正理庄地区沙一段顶部发育一套厚约30-60m的薄层碳酸盐岩与砂泥岩互层的沉积层,该层段的碳酸盐岩成分以生物灰岩为主。根据水深和水动力条件,将碳酸盐岩划分为滨湖亚相、浅湖亚相和半深湖亚相,其中浅湖亚相又划分为生物浅滩微相和滩缘微相。生物浅滩具有分布范围广、顶面平坦、沉积厚度较小的特征。浅湖沉积的生物灰岩孔渗性、连通性好,是良好的油气储集层。该段沉积发育于湖盆的微陷扩张期,构造运动相对平静,以基底间歇性沉降为主,导致湖水深度阶段性的变化,最终形成碳酸盐岩与砂泥岩互层的沉积。

A set of carbonate lamination and sand-shale interbedding, with thickness from 30 to 60 meters, is found in the top of sand layer-1 (Es1), Zhenglizhuang area, Dongying sag. The carbonate rock is mostly composed of biogenic limestone, which can be divided into shore-lake subfacies, shallow-lake subfacies and semideep subfacies, based on water depth and hydrodynamic condition, where shallowlake subfacies could be further divided into biogenic shoal microfacies and bank-inset microfacies. Such a biogenic shoal microfacies is characterized by extensive distribution, smooth top and thin sedimentary thickness. The biogenic limestone originated from shallow lacustrine sediment has preferable porosity and permeability as well as connectivity, being as a good reservoir. The sediment shapes in stage of minute depressing and extension of the lake basin, for which the tectonic movement is relatively calm, but existed intermittent basement subsidence leads to episodic changes in water depth, resulting in deposits of carbonate and sand-shale interbedding.