Abstract: The Devonian shale widely distributed in northwestern Central Guangxi depression is the primary target for seeking breakthrough of shale gas in the Yunnan-Guizhou-Guangxi region. In order to identify the accumulation conditions and potentials of shale gas in this region, more than 300 core samples were evenly taken (at sampling interval of 2 m) in Well GY 1 for organic geochemistry and rock mineralogy analysis. Well GY 1 is the first exploration well drilled through all Devonian shale gas formations in the Central Guangxi depression. The analysis results indicate that the Devonian shale is characterized by big thickness (470-1300 m), high TOC (0.23%-10.63%) and high maturity (R_o=1.88%-2.83%), which are favorable for the generation and accumulation of shale gas. Moreover, the shale has high content of brittle minerals and presence of organic pores and micro-fractures, implying the high probability of the shale gas reservoir to be stimulated. However, faulting activities during multi-stage tectonic movements damaged the shale reservoir, especially the gas-bearing potential. In view of exploration potentials, analysis of three sets of major shale gas formations (Liujiang Formation, Luofu Formation and Nabiao Formation) indicates that the Lower Liujiang Formation is the primary shale gas exploration target for its relatively favorable organic geochemical and physical properties and hydrocarbon accumulation conditions.

Key words: Central Guangxi depression, Devonian, shale, shale gas, accumulation condition