Organic geochemical characteristics of coal in the badaowan formation of the Naomaohu Sag, Santanghu basin

In order to clarify the source, sedimentary environment and thermal evolution characteristics of hydrogen-rich organic matter in No.1 coal of Badaowan formation in Naomaohu Sag, Santanghu basin, this study used organic geochemical methods such as coal petrographic maceral identification, vitrinite reflectance determination, and gas chromatography-mass spectrometry (GC-MS) analysis of saturated hydrocarbons and aromatic hydrocarbons. Maceral composition and biomarker compounds analyses indicate that ferns with high hydrogen indices, conifers rich in resins, and lower aquatic organisms abundant in saturated hydrocarbons are the primary sources of hydrogen-rich organic matter in the coal. The results show that the reducing environment with strong overlying water and certain water flow is conducive to the preservation and enrichment of hydrogen-rich components (spores, cuticles, etc.) in higher plants, and also provides conditions for the infiltration and enrichment of soluble organic matter released by early diagenetic exinite to vitrinite. The vitrinite reflectance (0.40% ～ 0.48%) indicates that the organic matter is in the immature-low mature stage, and some hydrogen-rich organic matter has the ability to generate oil, which is a favorable stage for the formation of oil-rich coal.