Shale gas exploration prospect of Niutitang formation in Yuanma basin

According to deep studies on dark mudstone and shale of Niutingtang formation of lower Cambrian from outcrops around Xuefeng uplift and preserving conditions analysis,Yuanma basin in Xuefeng uplift was found to be a united passive continental margin in early Paleazoic and it belonged to shelf-basin environment in Niutitang stage of early Cambrian,which provided favorable facies belt for sedimentation of dark mudstone and shale of lower Cambrian.The dark mudstone and shale in Niutitang formation possesses the characteristics of high TOC,high brittle minerals contents,well developed pores,micro-fractures and good absorbing capacity,at the same time it has favorable bottom and up plates,favorable depth,undeveloped faults in deep depression and favorable preserving conditions.The study results indicate Caotang depression and Chengxi depression in Yuanma basin have good geological conditions for shale gas accumulation,and they are important areas for shale gas explora-tion in lower Cambrian in southern China.