Organic matter enrichment model of the shale in Wufeng-Longmachi formation of Wuxi area
QIU Zhen
JIANG Zengguang
DONG Dazhong
SHI Zhensheng
LU Bin
TAN Xin
ZHOU Jie
LEI Danfeng
LIANG Pingping
WEI Hengye
Abstract：30 samples of gas shale from the Wufeng formation to Lungmachi formation shale in Wuxi regions of Sichuan province were tested in terms of their organic carbon content (TOC)and trace element geochemistry.The characteristics of the organic matter enrichment and their controlling factors in different horizons were further analyzed.It is concluded that by controlling the hypoxia degree of sedimentary water,sea level changes affect the organic matter enrichment in shale.The results show that four different horizons of organic matter deposition are identified with high TOC of up to 3.7 ％ on average,but the correlation between TOC and palaeo-productivity (such as the content of Babio) is not obvious,implicating that the palaeoproductivity is not the major controlling factor.Although water redox condition varies in different sedimentary horizons,it has a good correlation with the TOC,indicating that the organic matter accumulation is mainly controlled by the degree of hypoxia,and the enrichment mechanism belongs to "preservation mode".In summary,the depositional model of organic matter in Wufeng-Lungmachi shale is that sea level changes control the hypoxia degree of sedimentary water.The sea level drop will lead to oxygen enrichment in the bottom water,while the sea level rise will cause hypoxia,thus affecting the organic matter enrichment in shale.
Keywords：organic matter enrichmentWufeng-Lungmachi shaleshale gasredox conditionpalaeo-productivitySichuan basin
Publication Date：2017-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：10( 1134-1143 )