Sedimentary characteristics and forming conditions of beach-bar sandbodies in the upper fourth member of the Shahejie Formation in the south slope of the Huimin Sag

Yuan Jing; Liang Huiyuan; Tan Mingyou; Chen Xiaojie; Dong Daotao; Sun Mingjiang; Gao Ruohan

doi:10.11743/ogg20140316

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Sedimentary characteristics and forming conditions of beach-bar sandbodies in the upper fourth member of the Shahejie Formation in the south slope of the Huimin Sag
Vol. 35, Issue 3, Pages: 410-416(2014)
Online First：08 June 2014，

Published：2014
DOI： 10.11743/ogg20140316
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DOI：

Yuan Jing, Liang Huiyuan, Tan Mingyou, et al. Sedimentary characteristics and forming conditions of beach-bar sandbodies in the upper fourth member of the Shahejie Formation in the south slope of the Huimin Sag[J]. 2014, 35(3): 410-416. DOI： 10.11743/ogg20140316.

摘要

在精细岩心描述的基础上，通过综合分析岩石粒度特征、录井、测井、地震以及大量区域地质背景资料，对惠民凹陷南坡沙四上亚段滩坝砂体的沉积特征、展布规律和形成条件进行了系统研究。结果表明：研究区滩坝砂以粉-细砂岩和粉砂岩为主，泥质含量较高，物性较差。垂向上，4砂组—2砂组沉积时期滩坝砂体零星发育，1砂组发育大面积漫湖滩坝；平面上，滩坝砂体沿夏口断层呈带状分布。从湖平面条件来看，枯水面之下的稳定水深和较强波浪作用更利于坝砂发育；从构造条件来看，夏口断层形成的地形坡折一方面促进了滩坝砂体沿断层下降盘聚集，另一方面也限制了滩坝的横向展布宽度；从物源供给来看，洪水漫湖条件下基岩和先成沉积物的线状供源比末端扇在洪泛期砂体入湖更利于滩坝大面积发育。

Abstract

Sedimentary characteristics

distribution patterns and forming conditions of beach-bar sandbodies in the upper fourth member of the Eocene Shahejie Formation on the south slope of the Huimin sag have been systematically analyzed in this paper based on detailed core description and analyses of grain sizes

well log

seismic and the regional geological background data.The result indicates that the beach-bar sandstones are dominated by siltstones and fine-grained silty sandstones of high mud content

thus have unfavorable physical properties.Vertically

the beach-bar sandbodies are common in the first sand group but sporadic in the second

the third and the fourth sand groups.Laterally

beach-bars in the studying area distribute along the Xiakou fault.Stable water depth and stronger waves were beneficial to the formation of beach-bar sandbodies.The slope break caused by the Xiakou fault was helpful for beach-bar sandbodies to be formed along the thrown side of the fault but also restricted the horizontal spreading of the beach-bar.Sediments from the basement and earlier deposited layers in flood-overflow lake provided better sediment source for the beach-bar to develop than that from the terminal fan during floo-ding period.