MINERALOGY AND SHALE GAS POTENTIAL OF LOWER SILURIAN ORGANIC-RICH SHALE AT THE SOUTHEASTERN MARGIN OF SICHUAN BASIN, SOUTH CHINA

Exploration for unconventional gas resources from Paleozoic formations in the Sichuan Basin in South China is just getting started. Large, potential gas reservoirs are presumed to exist in the southern and southeastern Sichuan Basin where Silurian marine organic-rich shale occurs. This paper provides geochemical and mineralogical data and other relevant information on potentially economic black shale formations of the Lower Silurian. The results show that in the shale, mineral components are dominated by clay minerals and quartz with minor amounts of plagioclase, potash feldspar, calcite and pyrite. The brittle mineral content ranges from 38 to 73% by weight (average content 56.2 wt%). In general, the Lower Silurian organic-rich shale of the Longmaxi Formation in the Sichuan Basin is highly mature, with the vitrinite reflectance between 1.6 and 3%. The shale has a high content of organic carbon, with an average of 1.8%, is tens of meters thick and of large areal extent. It can be regarded as a potential gas shale target.