Characteristics of Hydrogen-rich Coals in Southern China: Implications from Organic Geochemistry and Carbon Isotopic Compositions

The organic geochemical characteristics of hydrogen-rich coal in southern China were investigated synthetically through organic geochemistry and carbon isotope analyses. The results showed that the hydrogen contents of the test samples were more than 5.0% and the H/C atomic ratios were between 0.76–1.06. Samples were found to be composed mostly of Type II-III kerogen, consistent with good hydrocarbon-generation potential. The R (0.54–1.10%) and T (430–453°C) values imply that the hydrogen-rich coals were in low maturity to mature stages. Stable carbon isotopic ratios (δC) of the samples used varied from –24.5‰ to –23.4‰, the barkinite content ranging from 13.9% to 83.3%, indicating a predominantly terrestrial origin with marine influence during coal formation. Some organic geochemical parameters showed corresponding changes as the hydrogen content increased from 5.0% to 7.0%, however, the source inputs changed significantly when hydrogen content was greater than 6.0%. Terrestrial higher plants gradually become predominant within the coal-forming materials, whereas this dominant position is not apparent at lower hydrogen contents, which is attributable to the strong seawater effect during the hydrogen-rich coal formation process.