Effects of clay minerals and biosurfactants on isotopic and molecular characteristics of methane encaged in pressure vessel gas hydrates |
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| Institution: | 2. Xuzhou Shihua Pipeline Special Operation Co., Ltd., Xuzhou, 221008, Jiangsu, China;1. Chemical Engineering Department, Indian Institute of Technology, Roorkee, India;2. Chemical Engineering and Process Development Division, CSIR-National Chemical Laboratory, Pune, India;3. Keshav Dev Malviya Institute of Petroleum Exploration, Oil and Natural Gas Corporation (ONGC), Dehradun, India;1. School of Earth Sciences and Key Laboratory of Mineral Resources in Western China (Gansu Province), Lanzhou University, Lanzhou 730000, China;2. U.S. Geological Survey, Box 25046, MS 939, Denver Federal Center, Denver, CO 80225, USA;3. Bureau of Economic Geology, The University of Texas at Austin, Austin, TX 78713, USA;1. Department of Chemical Engineering, Amirkabir University of Technology (Tehran Polytechnic), 424 Hafez Avenue, Tehran 15875-4413, Iran;2. Department of Petroleum, Amirkabir University of Technology (Tehran Polytechnic), 424 Hafez Avenue, Tehran 15875-4413, Iran |
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| Abstract: | The stable isotope values of carbon (δ13Cmethane) and hydrogen (δ2Hmethane) from methane molecules trapped in gas hydrates are useful for differentiation of methane from microbial and thermal origins, providing valuable information during hydrocarbon exploration. Recent studies have reported catalysis of methane hydrates when smectite clays and biosurfactants are present in hydrate-hosting sediments, but catalytic influences on the values of δ13Cmethane and δ2Hmethane are not well documented. In this study, pressure vessel methane hydrates were formed from solutions in contact with smectite clays (montmorillonite and nontronite) and biosurfactants (rhamnolipids and surfactin). Experiments show less than 1‰ differences in values of δ13Cmethane between free and encaged molecules and up to 10‰ variations in values of δ2Hmethane between free and encaged molecules. Notably, methane consumption increased in methane hydrates formed from solutions containing biosurfactants and biosurfactant–smectite mixtures. Results presented here indicate that a hydrate formed in the presence of smectite clays and biosurfactants are characterized by small shifts in free and encaged values of δ13Cmethane and δ2Hmethane and do not complicate interpretation of gas origin. In contrast, methane consumption in hydrates formed under the catalytic effect of smectite clays and biosurfactants modifies gas wetness, obscures gas origin and complicates interpretation of thermal maturity. |
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