The Es1 sandstone is a fruitful hydrocarbon zone of Eocene Shahejie Formation. Therefore, the present study comprises the subsurface facies analysis established on the description of seven wells. Methods include core observation, thin section petrography, scanning electron microscope (SEM), cathodoluminescence (CL), and X-ray diffraction to evaluate the microfacies, lithofacies, and rock characteristics. Two microfacies of lithofacies have been established as sandstone microfacies and mudstone microfacies on the basis of grain size. Among them, sandstone is further divided into four sub-microfacies on the basis of microscopic studies, rock fragments and mineral composition, which are arkose sandstone, lithic arkose, feldspathic litharenite, and litharenite. These microfacies consisting quartz, feldspar as abundant detrital grains followed by rock fragments and micas, whereas calcite, ferro-calcite, quartz overgrowth, and clay are the main cement. The Es1 sandstone consists of good primary porosity and permeability as well as good secondary porosity caused by fracturing and dissolution of unstable minerals that enhance the reservoir quality. Whereas cementation and compaction reduce the reservoir characteristics. Studied formation divided into five lithofacies including conglomerate sandstone lithofacies, medium to coarse-grain sandstone lithofacies, fine sandstone lithofacies, siltstone lithofacies, and mudstone lithofacies. Core observation, sedimentary structures, facies sequences of the well log, and sedimentary composition reveal that Es1 deposited into the lacustrine delta fan depositional environment. Rock grain size indicates that Es1 contains mixtures of grains including pebbles, sand-size as well as minor silt and clay size. Grain size varies from conglomerate to clay size. The Es1 sandstone was deposited in braided river (conglomerates sandstone), channel bar, lacustrine, fluvial channel (massive bedding, cross-bedding, and graded bedding sandstone), deltaic, and flood-plain (siltstone and mudstone) sedimentary environment. It is concluded that higher transport energies in channels deposited coarse-grain sediments in shallowest part of the lake setting. However, the energy decreases towards greater depth which deposited mudstone in central part of the lake.

中文翻译：

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渤海湾盆地沙河街组沉积学——以南堡凹陷沙1段为例

沙河1砂岩是始新世沙河街组富有成效的油气带。因此，本研究包括根据七口井的描述建立的地下相分析。方法包括岩心观察、薄片岩相学、扫描电子显微镜 (SEM)、阴极发光 (CL) 和 X 射线衍射，以评估微相、岩相和岩石特征。根据粒度大小确定了两种岩相微相，即砂岩微相和泥岩微相。其中，砂岩根据显微研究、岩屑和矿物组成进一步划分为长石砂岩、岩屑长石、长石岩屑岩和岩屑岩4个亚微相。这些由石英组成的微相，长石为丰富的碎屑颗粒，其次是岩石碎片和云母，而方解石、铁方解石、石英过度生长和粘土是主要的胶结物。Es1砂岩具有良好的原生孔隙度和渗透率以及良好的次生孔隙度，这些孔隙度是由不稳定矿物的压裂和溶解引起的，提高了储层质量。而胶结和压实降低了储层特征。研究地层分为砾岩砂岩相、中粗粒砂岩岩相、细砂岩岩相、粉砂岩岩相和泥岩岩相5种岩相。岩心观察、沉积构造、测井相序和沉积组成表明，Es1 沉积于湖相三角洲扇沉积环境中。岩石粒度表明 Es1 包含颗粒的混合物，包括鹅卵石、沙子大小以及少量粉砂和粘土大小。颗粒大小从砾岩到粘土大小不等。沙沙一期砂岩沉积于辫状河（砾岩砂岩）、河滩、湖泊、河流河道（块状层理、交错层理、分级层理砂岩）、三角洲和漫滩（粉砂岩、泥岩）沉积环境。得出的结论是，河道中较高的输运能量在湖泊环境的最浅部分沉积了粗粒沉积物。然而，能量随着深度的增加而减少，从而在湖中央沉积泥岩。Es1砂岩沉积于辫状河（砾岩砂岩）、河滩、湖相、河流河道（块状层理、交错层理、分级层理砂岩）、三角洲和漫滩（粉砂岩、泥岩）沉积环境。得出的结论是，河道中较高的输运能量在湖泊环境的最浅部分沉积了粗粒沉积物。然而，能量随着深度的增加而减少，从而在湖中央沉积泥岩。Es1砂岩沉积于辫状河（砾岩砂岩）、河滩、湖相、河流河道（块状层理、交错层理、分级层理砂岩）、三角洲和漫滩（粉砂岩、泥岩）沉积环境。得出的结论是，河道中较高的输运能量在湖泊环境的最浅部分沉积了粗粒沉积物。然而，能量随着深度的增加而减少，从而在湖中央沉积泥岩。