Simulation Research On Biogenic And Thermogenic Gas From Brown Coal In Dananhu Depression Of Tuha Basin

In order to elucidate interaction between microorganisms and organic matter in coals, as well as characteristics and mechanism of gas production in the process of coal thermal evolution, brown coal in Dananhu depression of Tuha basin taken as research object to conduct simulation experiment on biological hydrocarbon generation and pyrogenic hydrocarbon generation, gas production mechanisms were discussed to obtain appropriate discrimination standard of CBM genetic types in the research area.Based on enrichment and culture of methanogen, characteristics of gas component variation and carbon-hydrogen isotope composition during the process of gas generation in simulation experiment of biologenic hydrocarbon generation tracked and analyzed, maceral types and gas production mechanism of microbiological degradation in different gas production periods were revealed. The results reflect that huminite is biodegraded to produce gas in the first period, and in the second period are inertinite and liptinite. There was negative correlation trend between value of δ13C(CH4) and huminite content, and positive correlation trend with inertinite content.Through simulation experiment on pyrogenation hydrocarbon generation, gas generation process and mechanism of coal thermal evolution were researched and revealed, and correspondence between gaseous hydrocarbon carbon-hydrogen isotopes composition and thermal evolution periods of coal samples as well as evolution characteristics were concluded and summed. The result show that, with coal evolution degree increasing, values of δ13C(CH4) and δ13C(C2H6) decrease and then increase with temperature increasing, however, value of δD(CH4) gradually increases all the time.Simulation experiment data analyzed systematically by means of mathematical statistics, the identification indexes of primary and secondary biogenic gas as well as biogenic and thermogenic CBM were proposed from aspects of geological structure, coal-forming basin environment, source rock evolution and composition characteristics of gaseous hydrocarbon carbon-hydrogen isotopes, furthermore, discrimination models of coal evolution degree division and CBM genetic types suitable for the research area were come up with.