LAUSR

Abstract The increasing global demand for clean energy has made it imperative to exploit unconventional oil and gas resources. Early thermogenic gas is one of the research target of unconventional gas. The Jurassic coal measures were widely distributed in the eastern Junggar Basin with high abundance of humic organic matter and low thermal degrees, showing potential for early thermogenic gas exploration. The burial depth of Jurassic source rocks ranges between 2200 m and 4500 m, with vitrinite reflectance ranging from 0.5% to 0.9%. To study the potential and possibility of gas generation from Jurassic coal measures at low mature stage in the eastern Junggar Basin, mudstone and coal samples were selected for pyrolysis experiments. The pyrolysed temperatures setting for this study are 330 °C, 350 °C, and 370 °C. The heating times at each desired temperature are 3, 7, 14, 21, and 30 days. Parameters such as vitrinite reflectance and certain biomarker ratios indicate all the samples are still at the low mature stage when the heating process finished. Genetic correlation between δ13C1 and C1/(C2+C3) ratio reveals that the generated gas in this study is mainly sourced from Type III kerogen and at the stage of low maturity. Hydrocarbon gas yield results suggest that 370 °C is the most favorable temperature for early thermogenic gas generation, especially heating for 14 days or longer. Pyrolysis results indicate time effect plays an important role in the formation of early thermogenic gas. The results of fourier transformed infrared spectra suggest aliphatic components in macromolecular structure of kerogen provide gas generating material during low mature stage. The evolution history of the Jurassic source rocks and the pyrolysed results indicate the Jurassic coal measure strata in the eastern Junggar Basin has favorable geothermal condition for accumulation of early thermogenic gas.