Thermal simulation experiments are conducted with cores (mudstone, oil shale and coal) at gas hydrate-bearing intervals in gas hydrate drilling holes of DK-2 and DK-3 in the Qilian Mountain permafrost. Gas composition and carbon isotopes of hydrocarbon gases from gas hydrate are compared with simulated gases from samples. The possible relationship between these potential gas source rocks and gas source of gas hydrate is studied. The results indicate that thermally simulated gases are mainly composed of CO2 with a small amount of hydrocarbon gases on the low temperature conditions (lower than 300°C); yields of hydrocarbon gases from mudstone, oil shale and coal gradually increase, displaying differences between adsorbing gases with different rocks. With increasing of thermal simulation temperatures, yields of hydrocarbon gases from mudstone, oil shale and coal obviously increase and reach maximum values at 500 °C; conversely, yields of CO2 vary little. With increasing of thermal simulation temperatures, carbon isotope values of hydrocarbon gas first become lighter and then heavier and are characteristic of normal carbon isotopic series of δ13C1 δ 13C2<δ13C3. The consequences suggest that hydrocarbon gases from mudstone at 350 to 400 °C or oil shale at 380 to 400 °C have similar features of gas composition and carbon isotope with gas hydrate, indicating that the gas source of gas hydrate has geochemically genetic relation with deep mudstone or oil shale. In contrast, gas composition of hydrocarbon gases from coal and gas hydrate are similar, but both carbon isotope values are incomparable, suggesting that the relationship between coal and gas source of gas hydrate is not the same.
Origin of Gases from Gas Hydrate in the Qilian Mountain Permafrost, Qinghai: Comparison of Gas Composition and Carbon Isotopes
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Liao, Zewen , and Hui Liu. "Origin of Gases from Gas Hydrate in the Qilian Mountain Permafrost, Qinghai: Comparison of Gas Composition and Carbon Isotopes." Paper presented at the Tenth ISOPE Ocean Mining and Gas Hydrates Symposium, Szczecin, Poland, September 2013.
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