Sedimentary environment and organic matter accumulation of Wufeng-Longmaxi shales,southwest Yangtze Plate,China:Insights from geochemical and petrological evidence  

作　　者：An-kun Zhao Dong Wang Qian Zhang Zi-hui Lei Qian Yu Di Zhang Ye-xin Zhou 

机构地区：[1]Chengdu Center of China Geological Survey,Ministry of Natural Resources,Chengdu 610081,China [2]Key Laboratory of Sedimentary Basin and Oil and Gas Resources,Ministry of Natural Resources,Chengdu 610081,China [3]The College of Literature and Journalism of Sichuan University,Chengdu 610064,China

出　　处：《China Geology》2024年第4期747-761,共15页中国地质（英文）

基　　金：jointly funded by the National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(PLC20210104);China Geological Survey(DD20221661);China National Science and Technology Major Project“Test and Application of Shale Gas Exploration and Evaluation Technology(2016ZX05034004)”。

摘　　要：Upper Ordovician-Lower Silurian Wufeng-Longmaxi Formation is the most developed strata of shale gas in southern China.Due to the complex sedimentary environment adjacent to the Kangdian Uplift,the favorable area for organic-rich shale development is still undetermined.The authors,therefore,focus on the mechanism of accumulation of organic matter and the characterization of the sedimentary environment of the Wufeng-Longmaxi Shales to have a more complete understanding and new discovering of organic matter enrichment and favorable area in the marginal region around Sichuan Basin.Multiple methods were applied in this study,including thin section identification,scanning electron microscopy(SEM)observations and X-ray diffraction(XRD),and elemental analysis on outcrop samples.Five lithofacies have been defined according to the mineralogical and petrological analyses,including mudstone,bioclastic limestone,silty shale,dolomitic shale,and carbonaceous siliceous shale.The paleo-environments have been reconstructed and the organic enrichment mechanism has been identified as a reduced environment and high productivity.The Wufeng period is generally a suboxic environment and the early Longmaxi period is a reducing environment based on geochemical characterization.High dolomite content in the study area is accompanied by high TOC,which may potentially indicate the restricted anoxic environment formed by biological flourishing in shallower water.And for the area close to the Kangdian Uplift,the shale gas generation capability is comparatively favorable.The geochemical parameters implied that new favorable areas for shale gas exploration could be targeted,and more shale gas resources in the mountain-basin transitional zone might be identified in the future.

关 键 词：SHALES Shale gas Sedimentary environment Graptolite Upper Ordovician‒Lower Silurian Organic matter accumulation Radiolarian Geochemical and petrographic evidence Wufeng-Longmaxi Formation Oil-gas exploration engineering Suboxic environment Sichuan Basin Reduced environment Yangtze Plate 

分 类 号：P618.13[天文地球—矿床学]