渤中凹陷断拗转换期湖扩—湖退型层序及其对规模湖底扇发育展布的控制  

Sequence stratigraphic model of Bozhong subbasin during a syn-rift to post-rift transition and its controls on regionally extensive sublacustrine fans

作　　者：龚承林[1,2] 徐长贵 官大勇 王启明 李东伟 GONG Chenglin;XU Changgui;GUAN Dayong;WANG Qiming;LI Dongwei(National Key Laboratory of Petroleum Resources and Engineering,China University of Petroleum(Beijing),Beijing 102249,China;College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China;China National Offshore Oil Corporation,Beijing 100010,China;Bohai Petroleum Research Institute,Tianjin Branch of CNOOC Ltd.,Tianjin 300459,China)

机构地区：[1]油气资源与工程全国重点实验室,中国石油大学(北京),北京102249 [2]中国石油大学(北京)地球科学学院,北京102249 [3]中国海洋石油集团有限公司,北京100010 [4]中海石油(中国)有限公司天津分公司渤海石油研究院,天津300459

出　　处：《古地理学报》2023年第5期992-1010,共19页Journal of Palaeogeography：Chinese Edition

基　　金：中海石油(中国)有限公司天津分公司项目“渤南低凸起北部古近系岩性圈闭分布、成藏机理分析及有利区带预测”(编号:CCL2020TJX0NST1276)资助。

摘　　要：湖、海层序充填存在巨大差异,因此亟待建立具有湖底扇预测功能的层序模式,以便解决渤中凹陷深层东营组规模湖底扇成因类型与时空展布的勘探难题。文中利用地震和钻/测井资料在渤中凹陷深层东营组共识别出5个不整合面和4个最大洪泛面,并据此将其划分为4个沉积层序,每个沉积层序均发育早期湖扩(退积—加积式准层序组)和晚期湖退(进积式准层序组)2个体系域,构成湖扩—湖退型层序模式。规模水道型湖底扇主要形成于湖扩体系域,紧邻层序界面发育,出现在盆外远源大型水系和坡折前方缓坡背景下,是湖平面上升条件下充沛物源供给、活跃重力流和坡折地貌的综合响应,发育补给水道和末端朵叶2个亚相,其中末端朵叶发育朵叶核部、朵叶核缘和朵叶边缘3个微相。若规模水道型湖底扇与其他成藏条件相匹配,则能够形成大型岩性圈闭群,这是渤中凹陷深层最有利的大型岩性勘探目标。规模滑塌型湖底扇主要形成于湖退体系域,出现在盆外远源大型水系和坡折前方陡坡背景下或边界大断层下降盘,是湖平面下降条件下物源供给贫乏、重力流罕见和坡折地貌的综合响应,发育相对富泥的块体流沉积和相对富砂的砂质碎屑流沉积2个亚相。若是在汇聚背景和有利输导条件下发育的规模滑塌型湖底扇,也可形成大型湖底扇岩性圈闭群,这是渤中凹陷深层较有利的大型岩性勘探目标。The marked difference in sequence stratigraphy between lacustrine and marine basins requires the establishment of sequence stratigraphic model with function of predicting sublacustrine fans,aiming to a better prediction of areally extensive sublacustrine fans in the Oligocene Dongying Formation of the Bozhong subbasin.Five unconformities and four maximum flooding surfaces are recognized,based on seismic and borehole datasets.They divide the Oligocene Dongying Formation into four third-order sequences,each of which contains an expanding systems tract(retrogradational to aggradational parasequences)and regressive systems tract(progradational parasequences),resulting in an expanding-regressive sequence model.Regionally extensive channelized sublacustrine fans(i.e.,channel-lobe complexes)are composed of feeder channels and terminational fans,which consist of lobe axes,lobe fringes,and lobe distal fringes.They are mainly seen to occur in expanding systems tracts immediately above the sequence boundaries,and mainly occur on the gentle slope in front of syndepositional slope-break zones.They represent comprehensive responses to high sediment supply and vigorous sediment-gravity flows under humid climatic conditions,and to syndepositional slope-break zones.Regionally extensive channelized sublacustrine fans,coupled to favorable hydrocarbon-accumulation conditions,can form big subtle traps,which are the most favorable exploration targets of Oligocene Dongying Formation of the Bozhong subbasin.Regionally extensive non-channelized sublacustrine fans(i.e.,mass-transport complexes)contain mass-transport deposits and sandy debrites.They mainly seen to occur in regressive systems tracts immediately above the maximum flooding surfaces,and mainly occur on the steep slope in front of syndepositional slope-break zones or the hanging wall of boundary faults.They represent comprehensive responses to low sediment supply and diluted sediment-gravity flows under arid climatic conditions and to the mass-wasting processes induced by high

关 键 词：渤中凹陷 断拗转换期 层序模式 规模湖底扇 大型岩性圈闭 

分 类 号：P539.2[天文地球—古生物学与地层学]