A set of dark shales of intraplatform depression-deep shelf facies was deposited in Guizhong depression during the Devonian when the Guizhong depression experienced intracontinental rifting.Outcrop observation and integrated analysis of drilling and geochemical data indicate that the Middle-Lower Devonian shale in Guizhong depression feature in large thickness(the maximum cumulative thickness up to 1 000 m)

high abundance of organic matter(TOC of 0.53%~9.46%)

moderate thermal maturity(R

o

of 1.33%~3.62%)

well-developed micro-pores

nono-pores and micro-fractures

favorable clay mineral composition

moderate burial depth

and relatively good sealing conditions.All these characteristics reveal its high potential for shale gas exploration.Based on the shale gas exploration experiences of North American

in combination with the practice of marine shale gas exploration in south China

we put forward evaluation criteria for shale gas play.Paly evaluation results with these criteria show that the area to the west of Nandan-Xincheng-Mashan is a potential play for shale gas exploration in the Devonian in Guizhong depression.