东营凹陷缓坡带陆相红层砂岩粒度特征及沉积环境意义  

Grain-size characteristics and sedimentary environmental significance of terrestrial red sandstone in the Dongying Depression with a gentle slope zone

作　　者：张倩[1,2] 王永诗 王学军[2] 杨怀宇[2] 王天福[2] ZHANG Qian;WANG Yongshi;WANG Xuejun;YANG Huaiyu;WANG Tianfu(Postdoctoral Scientific Research Station of Shengli Petroleum Administrative Bureau,SINOPEC,Dongying Shandong 257001,China;Exploration and Development Research Institute of Shengli Oilfield Branch Company Ltd.,SINOPEC,Dongying Shandong 257015,China;Shengli Oilfield Branch Company Ltd.,SINOPEC,Dongying Shandong 257001,China)

机构地区：[1]胜利石油管理局博士后科研工作站,山东东营257001 [2]中国石化胜利油田分公司勘探开发研究院,山东东营257015 [3]中国石化胜利油田分公司,山东东营257001

出　　处：《地质科技通报》2024年第5期81-94,共14页Bulletin of Geological Science and Technology

基　　金：胜利石油管理局博士后科研课题“东营凹陷始新世早期干旱湖盆环境演化及沉积模式研究”。

摘　　要：东营凹陷古近系红层已被证实拥有巨大的勘探潜力。断陷盆地缓坡带广泛分布以砂、泥岩频繁互层为特征的红层沉积,而这种沉积物究竟形成于何种环境尚未形成统一认识。为明确这种干旱气候背景下发育的大规模陆相红层的沉积类型,以东营凹陷南部缓坡带王家岗地区W1、W2和W3井为例,系统解剖了孔一段-沙四下亚段红层储层的粒度分布特征、粒度参数特征及粒度概率累计曲线特征。结果显示:研究区红层储层砂岩具有单砂体厚度较薄(1~7.7 m)、粒度较细(平均粒径为2.24?~4.73?)的特点;粒度频率曲线主要为单峰正偏态型,表明沉积物以粗组分为主;粒度参数判别函数和判别图解均指示河流沉积环境;大多数样品的累计概率曲线具有显著的过渡组分(>50%),C-M图形与C=M线平行,表现出密度流特征。测井曲线主要为中-高幅箱型和钟型,指示加积和侧积作用占主导地位;岩心上常见反映快速堆积的块状层理、代表单向水流的平行层理和反映弱水流的小型交错层理等构造。基于研究区盆山相间的古地貌格局和炎热干旱的古气候背景的综合分析表明,红层砂岩形成于分支河流体系,其沉积特征表现为:从上游至下游,随着水动力条件的衰减,河道分汊加强,洪水侵蚀能力减弱,单砂体厚度和沉积物粒度逐渐减小,流体性质由密度流逐渐演变为牵引流。该研究的新认识为研究区红层油气勘探提供了新的思路,在开展此类型储层预测工作时,应重视古物源、古流向的分析,并加强对单期水道的识别和刻画。[Objective]In the gentle slope zone of the Dongying Depression,the first member of the Kongdian Formation and the lower part of the fourth member of the Shahejie Formation can be split by a distinctive assemblage of reddish sediments,which originated from both fluvial and lacustrine processes.Extensive research has substantiated the significant exploration potential of the Palaeogene red bed in the Dongying Depression.Nevertheless,the sedimentary facies type of the red bed remains a subject of debate among researchers.[Methods]To address this issue,we present a comprehensive analysis of wells W1,W2,and W3,which are located in the Wangjiagang area within the southern gentle slope zone of the Dongying Depression.This analysis mainly focused on evaluating the grain size distribution,grain size parameters,and grain size probability accumulation curves of the red bed.[Results]This study revealed the distinctive characteristics of the red sandstone reservoirs in the study area.These include thin single sand body thicknesses ranging from 1 to 7.7 m and fine particle sizes,changing from 2.24∅to 4.73∅.The grain size distribution is mainly characterized by unimodal positive skewness curves,suggesting the dominance of the relatively coarse fraction.The grain-size parameter discriminant function and bivariate grain-size parameter plots suggest a fluvial environment.The grain size accumulation probability curves of most samples exhibit a significant transition component(over 50%),and the graphs in the C-M bivariate plot are parallel to the C=M baseline,reflecting the characteristics of density flow.Moreover,the logging curves mainly exhibit box and bell shapes with medium to high amplitudes,indicating that the sedimentary processes primarily involved vertical accretion and lateral accretion.The core analysis revealed the presence of blocky bedding indicative of rapid sediment accumulation,parallel bedding characteristic of unidirectional flow,and small cross-bedding suggestive of weak flow.[Conclusion]In conclusion,it is

关 键 词：东营凹陷 陆相红层 粒度分析 干旱湖盆 分支河流体系 

分 类 号：P618.13[天文地球—矿床学]