Abstract: The Longmaxi formation of the Silurian in Middle-Upper Yangtze area is a set of high-quality hydrocarbon source developed in restricted shallow sea environment. Especially the black shale in the deposition centers of southern Sichuan, northern Sichuan, southeastern Chongqing to northern Guizhou is most developed, with big thickness and high organic matter abundance. The type of kerogen in the southern and northern Sichuan is dominated by type-I and the maturity of organic matter is in the middle-late stage of high maturity, which is dominated by generating pyrolysis gas-wet gas; The type of kerogen in the southeastern Chongqing to northern Guizhou is type-Ⅱ₁ and the maturity of organic matter reaches overmature, dominated by generating dry gas. According to the organic geochemical parameters in these areas and the logging data from drilling-encountered this formation as well as the shale gas explorative practices from North America, it is suggested that Longmaxi formation of the Silurian in Middle-Upper Yangtze area has favorable conditions to form shale gas reservoirs. There exist gas logging abnormality and many of abnormal pressure zones in this formation in drilling well of Jianshen-2.These show enormous potentials for shale gas exploration of Longmaxi formation in the Middle-Upper Yangtze area.

Key words: Middle-Upper Yangtze area, Longmaxi formation, shale gas, lithofacies paleogeography, organic carbon content