Mechanisms of fine-grained sedimentation and reservoir characteristics of shale oil in continental freshwater lacustrine basin:A case study from Chang 7_(3) sub-member of Triassic Yanchang Formation in southwestern Ordos Basin,NW China  

作　　者：LIU Xianyang LIU Jiangyan WANG Xiujuan GUO Qiheng Lv Qiqi YANG Zhi ZHANG Yan ZHANG Zhongyi ZHANG Wenxuan 

机构地区：[1]PetroChina Changqing Oilfield Company,Xi’an 710018,China [2]National Engineering Laboratory for Exploration and Development of Low-Permeability Oil&Gas Fields,Xi’an 710018,China [3]Yangtze University,Wuhan 430100,China [4]PetroChina Research Institute of Petroleum Exploration&Development,Beijing 100083,China

出　　处：《Petroleum Exploration and Development》2025年第1期95-111,共17页石油勘探与开发(英文版)

基　　金：Supported by the CNPC Major Science and Technology Project(2021DJ1806).

摘　　要：Based on recent advancements in shale oil exploration within the Ordos Basin,this study presents a comprehensive investigation of the paleoenvironment,lithofacies assemblages and distribution,depositional mechanisms,and reservoir characteristics of shale oil of fine-grained sediment deposition in continental freshwater lacustrine basins,with a focus on the Chang 7_(3) sub-member of Triassic Yanchang Formation.The research integrates a variety of exploration data,including field outcrops,drilling,logging,core samples,geochemical analyses,and flume simulation.The study indicates that:(1)The paleoenvironment of the Chang 7_(3) deposition is characterized by a warm and humid climate,frequent monsoon events,and a large water depth of freshwater lacustrine basin.The paleogeomorphology exhibits an asymmetrical pattern,with steep slopes in the southwest and gentle slopes in the northeast,which can be subdivided into microgeomorphological units,including depressions and ridges in lakebed,as well as ancient channels.(2)The Chang 7_(3) sub-member is characterized by a diverse array of fine-grained sediments,including very fine sandstone,siltstone,mudstone and tuff.These sediments are primarily distributed in thin interbedded and laminated arrangements vertically.The overall grain size of the sandstone predominantly falls below 62.5μm,with individual layer thicknesses of 0.05–0.64 m.The deposits contain intact plant fragments and display various sedimentary structure,such as wavy bedding,inverse-to-normal grading sequence,and climbing ripple bedding,which indicating a depositional origin associated with density flows.(3)Flume simulation experiments have successfully replicated the transport processes and sedimentary characteristics associated with density flows.The initial phase is characterized by a density-velocity differential,resulting in a thicker,coarser sediment layer at the flow front,while the upper layers are thinner and finer in grain size.During the mid-phase,sliding water effects cause the fluid front to rise

关 键 词：fine-grained sedimentation density flow mode flume simulation experiments reservoir characteristics Chang 7_(3)sub-member Triassic Yanchang Formation shale oil Ordos Basin 

分 类 号：P61[天文地球—矿床学]