摘要
【目的】近年来,多口探井在奥陶系乌拉力克组混积岩层位获得工业气流,突破了鄂尔多斯盆地西缘混积岩的勘探禁区。探明乌拉力克组混积岩岩相类型及沉积模式,可为西缘地区下步油气勘探工作提供理论基础和实际资料。【方法】基于典型钻井岩心和露头资料,综合利用薄片、扫描电镜及测井资料,对西缘乌拉力克组岩相、沉积相及展布规律进行研究。【结果与结论】鄂尔多斯盆地西缘奥陶系乌拉力克组岩石可分为混积岩相、陆源碎屑岩相和碳酸盐岩相三类,其垂向序列组合方式受控于两期海侵事件,而岩相变化则进一步受控于局部水动力条件。岩相类型、垂向序列、测井、地球化学等相标志显示,乌拉力克组发育台地、陆棚、斜坡和盆地四种沉积相带,并可进一步划分为7种亚相和15种微相。东部台地相发育“潮间滩—潮间坪”序列和“潮汐风暴—潮汐水道—潮汐砂坝”序列;中部陆棚相发育“陆棚风暴—滨岸/浅海砂坝”序列和“陆棚泥”序列;西部斜坡—盆地相以浊积扇、峡谷水道和盆泥为主。层序SQ1形成时期水体整体较深,发育大段泥页岩,层序SQ2沉积时期水体整体变浅,加之受微生物建造以及西缘—中东部相连影响,导致斜坡相—陆棚相亦整体变窄且向西后退。乌拉力克组的岩石类型和沉积特征主要受物源供给、古地貌特征和水动力条件影响,其中充足的物源供给是西缘地区混合沉积的基本条件。
[Objective]Several recent exploration wells in the Ordovician Wulalike Formation at the western edge of the Ordos Basin have obtained industrial gas flow,breaking through the largely unexplored migmatite zone.Under-standing the lithofacies and sedimentary characterisitcs of mignatites can provide theroretical basis and practical data for future oil and gas exploration work in the western edge.[Methods]Based on typical drilling core and outcrop da-ta,this study comprehensively utilizes thin sections,scanning electron microscopy,and logging to investigate the lithofacies,sedimentary facies,and distribution patterns of the Wulalike Formation in the western edge.[Results and Conclusions]The rocks of the Ordovician Wulaike Formation in the western edge of the Ordos Basin can be di-vided into three types:Migmatite lithofacies,terrigenous clastic lithofacies,and carbonate lithofacies.The vertical sequence combination is controlled by two periods of marine transgression events,while the lithofacies changes are further controlled by local hydrodynamic conditions.Lithofacies types,vertical sequences,logging,geochemistry and other facies indicators indicate that the Wulalike Formation can develop platforms,continental shelves,slopes,and basins,which can be further divided into 7 subfacies and 15 microfacies.The eastern platform facies feature"in-tertidal shoal-flat"sequence and the"tidal storm-channel-sand dam"sequence,and the sequence of"continental shelf storm shoreline/shallow sea sand bars"and"continental shelf mud"forms the central continental shelf facies.The western slope basin facies are dominated by turbidite fans,canyon channels,and basin mud.The distribution pattern of sedimentary facies within the third order sequence of the Wulaike Formation indicates that during the for-mation of sequence SQ1,the water body was generally deep and developed large sections of shale,while during the sedimentation of sequence SQ2,the water body became shallower as a whole.In addition,due to the influence of mi-crobial construction and the connection between the western edge and the middle-east platform,the slope and shelf facies also became narrower overall and retreated westward.Sedimentary model displays that rock types and sedimen-tary characteristics of the Wulaike Formation are mainly influenced by the source supply,paleogeomorphological fea-tures,and hydrodynamic conditions,among which sufficient source supply is the basic condition for migmatites sedi-mentation in the western edge area.
作者
白莹
马占荣
黄正良
闫伟
高建荣
赵振宇
BAI Ying;MA Zhanrong;HUANG Zhengliang;YAN Wei;GAO Jianrong;ZHAO Zhenyu(Research Institute of Petroleum Exploration and Development,PetroChina,Beijing 100083,China;Exploration Department of PetroChina Changqing Oilfield Company,Xi’an 710018,China;Institute of Exploration and Development,Changqing Oilfield Company,Xi’an 710018,China)
出处
《沉积学报》
北大核心
2025年第4期1213-1232,共20页
Acta Sedimentologica Sinica
基金
中国石油天然气股份有限公司科学研究与技术开发项目(2022KT0302)。
关键词
鄂尔多斯盆地
乌拉力克组
混积岩
岩相
沉积相
Ordos Bain
Wulalike Formation
migmatites
lithofacies
sedimentary facies
作者简介
第一作者:白莹,女,1990年出生,博士研究生,高级工程师,储层沉积学,E-mail:byshimmer@petrochina.com.cn;通信作者:赵振宇,男,高级工程师,E-mail:zhaozy01@petrochina.com.cn。
