Abstract:

The Lower Paleozoic WufengLongmaxi shale in the Sichuan Basin and its surrounding areas, China, is a key point of Chinese shale gas industry which has been promoted by more and more related achievements since the finding of highyield industrial shale gas in the Jiaoshiba area. However, there has been significant controversy on the classification of lithofacies which is regarded as the basis of shale and shale gas. This study has proposed two core indexes for shale lithofacies classification, including the content of quartz and the lamination style, based on a comprehensive review of lithofacies classifications at home and abroad and combined with the research and exploration results for the WufengLongmaxi shale. Then nine lithofacies of the WufengLongmaxi shale have been recognized based on the complete lithofacies classification process: (1) siliceouspoor nonparallel laminated shale, (2) siliceousmoderate nonparallel laminated shale, (3) siliceousrich nonparallel laminated shale, (4) siliceouspoor parallel laminated shale, (5) siliceousmoderate parallel laminated shale, (6) siliceousrich parallel laminated shale, (7) siliceouspoor indistinctly laminated shale, (8) siliceousmoderate indistinctly laminated shale, (9) siliceousrich indistinctly laminated shale. Three unique lithologic characteristics in the favorable exploration section include high quartz content, high TOC content and high friability in the Sichuan Basin and its surrounding areas.

Key words: Sichuan Basin, shale gas, WufengLongmaxi Formations, shale lithofacies