Recomment on the Study of Lithofacies Palaeogeography as a Guide for Geology Survey of Shale Gas

Key words: 
• shale gas /
• Longmaxi Formation /
• Silurian /
• southern Sichuan Basin and its peripheral region /
• sedimentary facies /
• lithofacies palaeogeography /
• regional geology survey

Abstract: The basic geological parameters, including total organic carbon conten (TOC) and type, thermal evolution of organic matter(R_o) thickness of hydrocarbon source rocks, mineral composition and content, reservoir characteristics, which all controlled by sedimentary facies, are the main elements to evaluate the enrichment of shale gas in regional geology survey stage. On the basis of the detailed study of sedimentary facies, by mapping the lithofacies palaeogeography, distribution of the fine-grained sedimentary rocks which are rich in organic matter can be figured out. So, the lithofacies paleogeography controls the developmental characteristics of the shale gas. Using the basic geological parameters, the shale gas favorable areas in southern Sichuan Basin and its peripheral region were preliminarily evaluated. The black rocks of shallow shelf facies in Longmaxi Formation of Silurian, as long as being up into middle diagenetic stage, would be able to be shale gas reservoirs in southern Sichuan Basin and its periphery. On the basis of our previous study, through analyzing the shale gas geologic feature of Longmaxi Formation in southern Sichuan Basin and its periphery, the point of view is further demonstrated, that the study of sedimentary facies or lithofacies palaeogeography is the key and foundation of shale gas geology survey and evaluation.