Shale gas was first discovered in southeast Chongqing, where is also the key place for shale gas exploration. Formation of shale gas reservoir is controlled by shale thickness, organic matters concentration, thermal evolution, porosity and preservation. Southeast Chongqing hosts two major shale units of rich organic matters, Niutitang formation of lower Cambrian and Wufeng-Longmaxi formation of upper Ordovician-lower Silurian, both bearing thick sediments, high organic matters concentration, high thermal evolution, especially in Wufeng-Longmaxi formation with favorable geology for potential economic shale gas, also in upper Proterozoic Doushantou formation, Permian Changxing formation, Longtan formatin (Wujiaping formation), and lower Silurian Shiniulan formation (Songkan formation), where shall be a good exploration target of shale gas.  

Songkan formation cores of Anye-1 well and outcrops, together with geochemistry, petrology and reservoir of Songkan formation shales, show dark gray thin-layered calcic shale interbeded with granular argillaceous limestone, with a rising lime and falling siltstone upwards. The TOC of Songkan formation in Anye-1 well district is generally lower than 1.0%, most at 0.1%. Its organic matters of calcic sandy mudstone are type II1, implying a higher thermal evolution with maturity at 2.75%-2.92%, average at 2.85%. The highly-interbeded mudstone and limestone can form a sealing layer in preserving shale gas. The horizontal cracks develop in mudstone, not in limestone, which is closely related to higher gas content indicated by the on-site tests. Although the organic carbon is not high in its mudstone and limestone, the gas has been enriched due to the sealing interbeded limestone. 

This paper, based on cores observation and tests, studies the lithology, geochemistry, reservoir and gasbearing features of Wufeng—Longmaxi Formation organic shale intersected by Xiye1 well, attempting to provide references in Guizhous shale gas exploration, targets prioritization and resources potential assessment. Organic shale is carboniferous and siliceous, distributing in the bottom of Wufeng formation and Longmaxi formation, belonging to deep water shelf sedimentation characterized by high organic abundance, high thermal maturity, good organic matters and high gas content. It implies a good shale gas reservoir formation. Authigentic quartz content in organic shale rises from subaqueous uplift to shallow water shelf and to deep water shelf, but clay minerals decrease. Organic shale reservoir space is displayed as organic porosity with gas in the form of adsorption. Shales sedimentary environment and preservation controls the gas content of southern China. 