摘要
歧口凹陷深凹区东三段主要发育半深湖-深湖亚相,重力流砂体连片发育,厘清其沉积特征及成因机制可为油气勘探提供理论支撑。以歧口凹陷深凹区东三段为研究对象,基于高精度地震、测-录井、岩心及薄片等资料,分析了深湖背景下重力流成因机制,总结了歧口凹陷深凹区沉积体系及分布模式。结果表明:东三段沉积时期,受盆缘边界断层及盆内沉积坡折控制,自北东向南浅水区辫状河三角洲前缘砂体发生垮塌,在深凹区形成多期重力流沉积叠置连片。区内重力流沉积可细分为6种岩相,解释为砂质碎屑流、泥质碎屑流、浊流3类成因,砂体整体分选较好,杂基含量低,具有液化构造、撕裂状泥砾、漂砾等典型滑塌型重力流沉积特征,根据不同类型岩相组合分布特征,平面上重力流呈现砂质碎屑流-浊流-泥质碎屑流的展布特征。其中砂质碎屑流水道微相储层物性条件最好,是深凹区的有利储集相带;浊流沉积的砂岩储层物性较差。歧口凹陷深凹区受古气候、古水深和古地貌的共同控制,具有源远-沟长-坡宜的时空匹配关系的沉积模式,具备形成大规模重力流沉积砂体的潜力。研究成果可为深凹区油气勘探提供参考。
[Objective]The Third Member of the Dongying Formation in the deep subsag area of the Qikou Sag is primarily characterized by semi-deep to deep lacustrine subfacies,with extensive development of gravity-flow sandbodies.Clarifying the sedimentary characteristics and formation mechanisms of these gravity-flow sandbodies can provide theoretical support for petroleum exploration.[Methods]By integrating the high-precision seismic,logging,core,and thin section data,we analyzed the genetic mechanism of gravity-flow sandbodies within the deep lake setting.Focusing on the Third Member of the Dongying Formation in the Qikou Sag,we also summarized the distribution pattern of the gravity-flow deposition system in the deep subsag area of the Qikou Sag.[Results]The results indicate that during the deposition of the Third Member of the Dongying Formation,the activities of basin boundary faults and internal sedimentary slope folds induced the occurrence of collapse in the sandbodies of the barided river delta front and the vertically superimposed gravity-flow deposits within the deep subsag.The gravityflow deposits in this area were subdivided into six lithofacies,corresponding to three genetic types:Sandy debris flows,muddy debris flows,and turbidity currents.The sandbodies exhibit well-sorted grains,low matrix content,and typical characteristics of slump-type gravity-flow deposits.Spatial analysis of lithofacies assemblages revealed a planar distribution pattern characterized by proximal sandy debris flows transitioning to turbidity currents and distal muddy debris flows.Among these,the sandy debris channels have the best reservoir properties and represent the most favorable reservoir facies in the deep subsag area.In contrast,the turbidity sandstone reservoirs have relatively poor physical properties.The coastal slope demonstrates a spatial-temporal matching relationship of far-source-gullylong-slope-appropriate,which possesses the potential for forming large-scale gravity-flow-deposited sandbodies.[Conclusion]The research results can provide a reference for oil and gas exploration in the deep subsag.
作者
张佼杨
朱华汇
石倩茹
张明振
董越崎
任仕超
葛卫双
ZHANG Jiaoyang;ZHU Huahui;SHI Qianru;ZHANG Mingzhen;DONG Yueqi;REN Shichao;GE Weishuang(PetroChina Dagang Oilfield Company,Tianjin 300280,China;School of Earth Resources,China University of Geosciences(Wuhan),Wuhan 430074,China)
出处
《地质科技通报》
北大核心
2025年第3期57-69,共13页
Bulletin of Geological Science and Technology
关键词
歧口凹陷
深凹区
重力流
砂质碎屑流
沉积模式
东三段
Qikou Sag
deep subsag area
gravity-flow
sandy debris flow
sedimentary pattern
Third Member of the Dongying Formation
