滇东—黔西地区早石炭世岩关阶晚期—大塘阶早期沉积环境及古地理格局

    Sedimentary environment and palaeogeographical pattern of the Early Carboniferous Late Yanguan—Early Datang stage in eastern Yunnan—western Guizhou area—enlightenment for shale gas exploration

    • 摘要: 下石炭统是滇黔桂地区页岩气勘查的重点层位,目前针对滇东—黔西地区下石炭统富有机质页岩展布的研究相对薄弱,开展沉积相与古地理研究能够明确页岩气勘查优势相带的展布。通过剖面沉积相划分、连井剖面对比、古地理图编制等工作,阐明了滇东—黔西地区早石炭世岩关阶晚期—大塘阶早期沉积环境特征,恢复了该地区古地理格局,确定了对页岩气勘查有利的半深水—深水相带。下石炭统打屋坝组可以划分为2个四级层序,富有机质页岩主要集中在下段海侵体系域。岩关阶晚期—大塘阶早期,滇东—黔西地区古地理格局呈现北西高、南东低,水体自北西向南东加深的特点,沉积相由潮坪相、台地相、斜坡相、半深水盆地相、深水盆地相自北东向南西渐变过渡,半深水—深水区位于盘县—普安—晴隆—关岭—六枝一带。

       

      Abstract: The Lower Carboniferous is the key layer of shale gas exploration in Yunnan-Guizhou-Guangxi area, but current research on distribution of Lower Carboniferous organic-rich shale in EYWG (Eastern Yunnan-Western Guizhou) is relatively weak.The study of sedimentary facies and palaeogeography can clarify the distribution of the dominant facies for shale gas exploration.In this paper, the sedimentary environment of Early Carboniferous rocks in the EYWG was studied and paleogeographic pattern was restored by dividing the sedimentary facies, comparing the cross-well profiles, and compiling paleogeographic maps.Through these efforts, semi-deep water-deep water facies of Lower Carboniferous in the EYWG have been identified for shale gas exploration.The Lower Carboniferous Dawuba Formation can be divided into two fourth-order sequences, and organic-rich shales are mainly concentrated in the lower TST.The paleogeographical pattern is higher in northwest and lower in southeast during Late Yanguan Early Datang stage in the EYWG.The water deepened from northwest to southeast, with the sedimentary facies transformed from tidal flat, platform, slope, semi Deep water basin to deep water basin, and the semi-deep water-deep water facies is located in Panxian-Puan-Qinglong-Guanling-Liuzhi area.

       

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