摘要
深水重力流的沉积类型及储集性能一直是沉积学领域研究的重点。此次研究以野外露头为基础,结合室内薄片分析,对鄂尔多斯盆地西缘奥陶系拉什仲组深水重力流沉积类型与储集性能进行了详细研究。拉什仲组以灰绿色砂岩及灰黑色泥岩为主,另见少量的粉砂岩和砾岩。槽模、交错层理、粒序层理及包卷层理等发育。通过岩性、沉积构造、古生物等分析,认为拉什仲组沉积环境为深水,沉积相主要为海底扇,水道和朵叶微相较为发育。水道可进一步分为复合型、垂向加积型、迁移型。复合型水道岩性以砂岩为主,粒度较粗,水道内部发育次级水道。垂向加积型水道岩性为细砂岩和粉砂岩,以垂向加积沉积为主。迁移型水道定向迁移特征明显,侧积体发育。从下至上,砂岩含量先减少,再增加,大致反映相对海平面升-降旋回,海底扇总体呈退积沉积序列。孔隙度及渗透率测试结果表明,复合型水道储集潜力最好,朵叶和迁移型水道次之。
The depositional types and reservoir properties of deep-water gravity flow deposits have been the focus of consideration of sedimentology for long.Based on the field study of outcrops and laboratory examination of thin-sections,these questions are studied in details in this paper for the Ordovician Lashizhong Formation on the western margin of the Ordos Basin.The Lashizhong Formation mainly consists of grayish-green sandstone and dark-gray mudstone,with a little of siltstone and conglomerate.Flute casts,cross bedding,graded bedding and convolute bedding are well developed.Based on the integrated study of lithologic characters,sedimentary structures and fossils,it is inferred that the Lashizhong Formation is deposited in an environment of deep-water,dominated by submarine fan with channel and lobe microfacies.The deep-water channel could be further divided into complex,vertically accretionary and migrational channel deposits.The complex channel is dominated by coarse sandstone with well developed secondary channels.The vertical accretionary channel is mainly filled by fine sandstone and siltstone as the result of vertical accretion.As to the migrational channel deposits,it is characterized by unidirectional migration and lateral accretionary bodies are well developed.From bottom to top,the sandstone decreases first and then increases,as the results of relative sea level fluctuation,and the submarine fans as a whole are in a sequence of retrogradation.The laboratory examination of porosity and permeability shows that the complex channel deposits have best reservoir properties,followed by lobe and migrational channel deposits.
作者
王鹏伟
李华
陈诚
刘映君
WANG Pengwei;LI Hua;CHEN Cheng;LIU Yingjun(School of Geoscience,Yangtze University,Wuhan 430100,China)
出处
《海洋地质前沿》
CSCD
2020年第1期59-66,共8页
Marine Geology Frontiers
基金
“十三五”国家科技重大专项(2017ZX05032-002-003)
国家自然基金(41472096、41502101)
长江青年基金(2015cqn26)
湖北省教育厅科学研究计划中青年人才项目(Q20171308)
长江大学大学生创新创业训练(2018022).
关键词
水道
重力流
海底扇
拉什仲组
奥陶系
鄂尔多斯盆地
channel
gravity flow
submarine fan
Lashizhong Formation
Ordovician
Ordos Basin
