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

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.