摘要
滩坝砂体是重要的油气储层,其形成的水动力机制复杂多变,受露头及现代沉积等资料的局限性影响,坝体的发育过程、几何形态、动态演化模式及构型叠置关系尚不明确。针对以上问题,利用沉积数值模拟与现代沉积相结合的方法,对典型正向线性临滨坝的沉积演化过程及成因机制进行了探讨。研究结果表明:典型海相临滨坝完整的发育阶段包括锥形坝形成期、弯月坝发育期、条带状复合坝形成期、条带状复合坝扩大生长期以及条带状复合坝停止发育期,现代沉积中可见不同发育阶段的坝体。不同演化阶段的坝体受向岸流、环流、沿岸流和底流等水动力控制。锥形坝及弯月坝为多个小规模、近等间距规则排列的坝体,受向岸流及沿岸环流不断冲刷,锥形坝演化为弯月坝。锥形坝及弯月坝间发育裂流凹槽,坝顶可发育回流沟槽,为典型的顶积式沉积过程。弯月坝坝体及坝间凹槽不断被沉积充填,形成相对整一的条带状复合坝,此阶段表现为典型的侧积式沉积过程。复合坝在向岸流及底流改造下变宽、变厚,最终出露水面形成障壁型滨岸。复合坝内部构型可由多个锥形坝、弯月坝及坝间凹槽构成,呈锥形坝-裂流凹槽-锥形坝或弯月坝-裂流凹槽-弯月坝的构型叠置关系,剖面上呈厚—薄—厚的叠置特征。
Beach-bar sandbodies are important hydrocarbon reservoirs formed under complex and varied hydrodynamic mechanisms.However,due to the limitations of data on outcrops and modern analogs,the understanding of their developmental processes,geometric morphologies,dynamic evolutionary patterns,and superposition within internal architectures remains unclear.Given this,we analyze the sedimentary evolution and hydrodynamic mechanisms of typical shore-normal,linearly distributed nearshore bars using sedimentary numerical simulations combined with modern analogs.Furthermore,we delineate the developmental and evolutionary patterns of these typical nearshore bars.The results show that a typical marine nearshore bar undergoes five stages of development:the formation of tapered bars,the development of crescentic bars,and the formation,expansion,and developmental termination of a banded compound bar.Modern analogs reveal bars at various developmental stages,which were formed under diverse coastal hydrodynamic conditions.Tapered bars and crescentic bars are a series of small-scale bars that are roughly equally spaced.The tapered bars evolve into crescentic bars due to the continuous erosion from uprush and longshore currents.In between the tapered and crescentic bars,there exhibit inter-bar rip channels and backflow trenches on the top.Both bar types represent typical topset deposits.Over time,the crescentic bars and their inter-bar rip channels receive deposits,forming a relatively uniform banded compound bar,demonstrated as typical lateral depositon This bar,after widening and thickening under the action of onshore and bottom currents,finally emerges above water and constitutes barrier shorelines.The internal architecture of a compound bar,which may comprise several tapered bars,crescentic bars and inter-bar channels,displays the tapered bar,interbar channel and tapered bar deposits superimposition or the crescentic bar,interbar channel and crescentic bar deposits superimposition that,corresponding to thick-thin-thick sequences
作者
赵俊威
孙海航
张东伟
王恒
ZHAO Junwei;SUN Haihang;ZHANG Dongwei;WANG Heng(Institute of Mud Logging Technology and Engineering,Yangtze University,Jingzhou,Hubei 434020,China;Exploration and Development Research Institute,Tarim Oilfield Company,PetroChina,Korla,Xinjiang 841000,China;Exploration and Development Research Institute,Liaohe Oilfield Company,PetroChina,Panjin,Liaoning 124000,China;School of Geosciences,Yangtze University,Wuhan,Hubei 430100,China)
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2024年第1期65-80,共16页
Oil & Gas Geology
基金
国家自然科学基金青年科学基金项目(41902155)。
关键词
沉积数值模拟
沉积构型
沉积水动力机制
临滨坝
海相滩坝
现代沉积
sedimentary numerical simulation
sedimentary architecture
hydrodynamic mechanism of deposition
nearshore bar
marine beach-bar
modern sediments
