关键词: 深层页岩气, 沉积相特征, 岩相分布, 五峰组—龙马溪组, 渝西区块

Abstract: 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 sedimentary facies and lithofacies is lacking, which affect the identification and preference of shale gas “sweet spot” sections. To this end, the sedimentary facies and lithofacies of the deep shale of Wufeng Formation-Longmaxi Formation in western Chongqing were studied in detail through core thin section, scanning electron microscopy, Xray diffraction, 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 subfacies: 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 facies 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 distribution of shale reservoirs in the study area and provide data support for the subsequent efficient development of shale gas.

Key words: deep shale gas, sedimentary facies characteristic, lithofacies distribution, Wufeng Formation-Longmaxi Formation, western Chongqing Area