干湿气候交替与内陆湖盆河流扇砂体的形成与分布——以鄂尔多斯盆地延长组为例  

Alternation of arid-humid climate, and formation and distribution offluvial fan sand in the central area of Inland Lake basin: A casestudy of the Yanchang Formation in Ordos basin

作　　者：李相博[1] 刘化清[1] 黄军平[1] 王雅婷 郝彬[1] 龙礼文[1] 王菁[1] 魏立花[1] LI Xiangbo;LIU Huaqing;HUANG Junping;WANG Yating;HAO Bin;LONG Liwen;WANG Jing;WEI Lihua(Research Institute of Petroleum Exploration&Development-Northwest,PetroChina,Lanzhou,Gansu 730020,China)

机构地区：[1]中国石油勘探开发研究院西北分院,甘肃兰州730020

出　　处：《地质学报》2023年第3期822-838,共17页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41772099,41872116);中国石油天然气股份公司重大科技项目(编号2019B-0307)联合资助的成果。

摘　　要：鄂尔多斯盆地是我国陆上最主要的油气盆地之一,三叠系延长组是该盆地的主要含油层位。本文通过大量野外露头及钻井岩芯观察与实测,结合室内鉴定分析,系统研究了延长组沉积时的古气候环境及沉积特征,取得了如下认识:①延长组沉积时期,气候具有三分性:早期为干旱环境;中期转变为温暖潮湿气候环境,生物繁盛,是烃源岩发育的最有利时期;晚期再次转变为半干旱—半湿润气候环境;②受干旱气候控制,延长组早期与晚期无大面积汇水区存在,洪水事件主导了盆地中心地区大规模砂体的形成与分布,尤其洪水的接力搬运与多次分选可能是造成延长组砂岩粒级普遍较细的主因;③延长组发育干旱与潮湿两种环境沉积模式,前者以低位域河流扇体系为特征,后者以湖侵期河流-三角洲-湖泊-重力流体系为特色;④干旱环境低位域河流扇砂体与潮湿环境水进域富含有机质泥岩相匹配,形成了延长组“满盆含砂、满凹含油”的特征。该研究发展了大型坳陷湖盆的沉积模式,对丰富陆相盆地沉积理论认识及指导油气勘探实践均有积极意义。Ordos basin is one of the most important oil and gas basins on land in China.The Yanchang Formation of Triassic is the main oil-bearing horizon of the basin.In this paper,based on the observation and measurement of a large number of field outcrops and drilling core data,combined with indoor identification and analysis,the paleoclimatic environment and sedimentary characteristics of the Yanchang Formation are systematically studied,and the following cognitions are obtained:①In the sedimentary period of the Yanchang Formation,the climate is divided into three parts:the early stage is arid environment;the middle stage is transformed into a biologically rich warm and humid climate environment,which isthe most favorable period for the development of source rocks;the later stage is transformed into semi-arid-semi-humid climate environment.②Controlled by arid climate,there is no large-scale catchment area in the early and late stage of the Yanchang Formation.Flood events dominated the formation and distribution of large-scale sand bodies in the central area of the basin,especially the relay transport and multiple sorting of floods may be the main reason for the generally fine grain size of sandstone in the Yanchang Formation.③There are two environmental sedimentary models of drought and humidity in the Yanchang Formation.The former is characterized by the fluvial fan system in the low stand system tract and the latter is characterized by the fluvial-delta-lake-gravity flow system in the lake transgression period.④Fluvial fan sand bodies in arid environment low-stand system tract match with the rich organic mudstones in wet environment transgressive system tract,forming the characteristics of the Yanchang Formation,which is full of sand and oil.This study completely changed the traditional understanding that the“Large Depression Model”was dominated by“delta model”in the past.It has a positive significance for enriching the theoretical understanding of continental basin sedimentation and guiding oil and ga

关 键 词：河流扇 干旱环境 洪水事件 接力搬运 沉积模式 延长组 鄂尔多斯盆地 

分 类 号：P618.13[天文地球—矿床学]