Sedimentary characteristics of carboniferous shale in Guizhou based on drilling information and geophysical comprehensive analysis

As an important shale gas exploration formation in southern China, there is no significant discovery and breakthrough in Carboniferous survey and evaluation.The unclear shale distribution of the Carboniferous Dawuba formation restricts shale gas survey and evaluation.Aiming at the characteristics of large distribution area, large thickness and thick cover of carbonate rocks in Carboniferous shale in Guizhou, the analysis which combined drilling information and geophysics is created.Shale sedimentary characteristics and distribution is the key basic geological problem which restricting the exploration and development of Carboniferous shale gas in Yaziluo rift trough.This method mainly base on wide-field electromagnetic exploration, supplemented by MT and 2D seismic exploration, calibrated with information of outcrops and drilling wells.From the well-connected section, the thickness is generally 100-350 m.The thickness of the Dawuba formation shale gradually decreases along the direction of the rift trough to the southeast, and decreases rapidly from the center to both sides along the vertical direction of the rift trough.It shows that in the Carboniferous Dawuba period, the overall sedimentary facies is platform and basin interspersed with NW-SE play.The line through Shuicheng-Ziyun-Luodian is the centre of basin facies.To the northeast or southwest on both sides, the deep of the water became shallow and the sedimentary facies transformed to platform facies.Qinglong-Panxian area exists a secondary rift trough with NE-SW play.There are several isolated platform in the rift rough.