中晚三叠世鄂尔多斯盆地两期沉降及其形成机制  

Two stages of subsidence and its formation mechanisms in Mid-Late Triassic Ordos Basin,NW China

作　　者：邓秀芹[1,2] 楚美娟[1,3] 王龙[1,2] 陈修 王妍心 DENG Xiuqin;CHU Meijuan;WANG Long;CHEN Xiu;WANG Yanxin(National Engineering Laboratory for Exploration and Development of Low-Permeability Oil&Gas Fields,Xi’an 710018,China;Exploration division of PetroChina Changqing Oilfield Company,Xi’an 710018,China;Exploration&Development Research Institute of PetroChina Changqing Oilfield Company,Xi’an 710018,China)

机构地区：[1]低渗透油气田勘探开发国家工程实验室,西安710018 [2]中国石油长庆油田公司勘探事业部,西安710018 [3]中国石油长庆油田公司勘探开发研究院,西安710018

出　　处：《石油勘探与开发》2024年第3期501-512,共12页Petroleum Exploration and Development

基　　金：国家科技重大专项“大型岩性油气藏形成主控因素与有利区带评价”(2017ZX05001);中国石油天然气集团有限公司科技项目“致密油勘探开发技术研究”(2021DJ22)。

摘　　要：基于近年来新补充的大量深井资料,深入开展中晚三叠世鄂尔多斯盆地沉降作用研究,提出该沉积期鄂尔多斯盆地经历了两期重要沉降事件,并对两期沉降作用下的地层发育特征、岩性组合、汇水区分布、沉积演化等进行系统对比分析。认为两期沉降作用均是印支期秦岭构造活动在其北侧克拉通边缘的响应;延长组10段沉降幅度大,碎屑供给多,沉积速率快,以较粗碎屑充填为主,快速沉降伴随快速堆积,地层自东北向西南呈楔形增厚,沉降中心位于盆地西南环县—镇原—庆阳—正宁一带,地层厚800~1 300 m,沉降中心与沉积中心偏离,发育多个汇水区,此时尚未形成统一湖盆;延长组7段沉积期,在构造沉降与卡尼期暴雨事件共同作用下,形成了大面积深水坳陷,沉积速率慢,沉降中心与沉积中心基本重合,均位于麻黄山—华池—黄陵一带,沉降中心深水沉积厚120~320 m,以细粒沉积为主;两期沉降机制存在差异,早期沉降与秦岭地区中三叠世勉略洋向北俯冲相关,在挤压背景下强烈拗陷,晚期沉降为晚三叠世后碰撞弱伸展动力环境下的结果。Based on a large number of newly added deep well data in recent years,the subsidence of the Ordos Basin in the Mid-Late Triassic is systematically studied,and it is proposed that the Ordos Basin experienced two important subsidence events during this depositional period.Through contrastive analysis of the two stages of tectonic subsidence,including stratigraphic characteristics,lithology combination,location of catchment area and sedimentary evolution,it is proposed that both of them are responses to the Indosinian Qinling tectonic activity on the northern edge of the craton basin.The early subsidence occurred in the Chang 10 Member was featured by high amplitude,large debris supply and fast deposition rate,with coarse debris filling and rapid subsidence accompanied by rapid accumulation,resulting in strata thickness increasing from northeast to southwest in wedge-shape.The subsidence center was located in Huanxian–Zhenyuan–Qingyang–Zhengning areas of southwestern basin with the strata thickness of 800–1300 m.The subsidence center deviating from the depocenter developed multiple catchment areas,until then,unified lake basin has not been formed yet.Under the combined action of subsidence and Carnian heavy rainfall event during the deposition period of Chang 7 Member,a large deep-water depression was formed at slow deposition rate,with the subsidence center coincided with the depocenter basically in the Mahuangshan–Huachi–Huangling areas.The deep-water sediments were 120–320 m thick in the subsidence center,characterized by fine grain.There are differences in the mechanism between the two stages of subsidence.The early one was the response to the northward subduction of the MianLüe Ocean and intense depression under compression in Qinling during Mid-Triassic.The later subsidence is controlled by the weak extensional tectonic environment of the post-collision stage during Late Triassic.

关 键 词：鄂尔多斯盆地 长10段沉积期 长7段沉积期 沉降中心 沉积中心 沉降机制 秦岭造山带 印支运动 

分 类 号：TE122[石油与天然气工程—油气勘探]