钻井信息与地球物理综合分析的贵州石炭系页岩沉积特征

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

石炭系作为我国南方地区重要的页岩气勘查层系,多年页岩气调查评价未有显著的发现和突破,石炭系打屋坝组页岩分布规律不清制约了页岩气调查评价与勘探。针对贵州石炭系页岩分布面积大、厚度大、碳酸盐岩覆盖厚的特征,探索形成钻井信息与地球物理综合分析技术,以大面积的广域电磁勘探为主,大地电磁MT、二维地震等地球物理勘探方法为辅,结合地表露头和钻井信息标定,对制约其页岩气勘探开发的页岩沉积特征与分布规律这一关键基础地质问题进行研究。从连井剖面上看,厚度一般为100~350 m,沿裂陷槽走向往南东打屋坝组页岩厚度逐渐减小,沿裂陷槽垂向由中心向两侧快速减小。石炭纪打屋坝期垭紫罗裂陷槽整体上呈现出北西-南东展布的台盆相间沉积格局,水城-紫云-罗甸一线为台盆相沉积中心,向北东、南西两侧水体变浅至台地相,晴隆-盘县一带存在北东-南西向展布的次级裂陷,槽内发育多个孤立台地。

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.