Characteristics of Sedimentary Facies and Lithofacies Distribution of Deep Shale of Wufeng Formation-Longmaxi Formation
The deep shale gas of Wufeng Formation-Longmaxi Formation in the western Chongqing is an essential area for the next exploration and development of shale gas in China.However,the shale petrographic components in this block are complex and spatially variable,and the fine description of the distribution characteristics of sedimen-tary facies and lithofacies is lacking,which affect the identification and preference of shale gas"sweet spot"sec-tions.To this end,the sedimentary facies and lithofacies of the deep shale of Wufeng Formation-Longmaxi Forma-tion in western Chongqing were studied in detail through core thin section,scanning electron microscopy,Xray dif-fraction,FMI imaging,nuclear magnetic resonance,organic carbon analysis and other research tools.The results show that the whole study area is in the deposition of offshore shelf phase,which can be divided into three subfa-cies:shallow water shelf,semi-deep water shelf,and deep water shelf that have different controlling effects on the shale gas;10 main lithofacies are developed,and the lithofacies are more stably deposited from the northwestern to the southeastern part of the area,and Longyi11 layer develops three main lithofacies:siliciclastic shale,mud-rich siliciclastic shale,and mud-siliciclastic shale.According to the distribution characteristics of the sedimentary faci-es and lithofacies,it is predicted that the resource potential of this section in Well Z203 Area is huge,and it is a favorable exploration area in the next step.The results of this study deepen the understanding of the vertical distri-bution of shale reservoirs in the study area and provide data support for the subsequent efficient development of shale gas.
deep shale gassedimentary facies characteristiclithofacies distributionWufeng Formation-Longmaxi Formationwestern Chongqing Area
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