Guest-exchange Behaviors of Different Hydrocarbons with CO2 + N2 Occurring in SII Mixed Hydrates
The replacement of SII CH4-C2H6-C3H8 hydrates in sandy sediments by CO2/N2 is studied to investigate the gas recovery from SII gas hydrate reservoirs. It was found that CH4 was the easiest one to be replaced in all experiments, and CO2/N2 played different roles during replacement in different CO2 concentrations. Particularly, the addition of N2 in replacement gas can cause the decrease in the replacement efficiency, which was related with the difference in swapping patterns. The increase of the N2 concentration may strengthen the structural stability of SII hydrates and lead to reducing the portion of SII hydrates transformed into SI hydrates.
Keywords: gas hydrate, CO2+N2, structure II, replacement efficiency
 Sloan, E. D. (2003). Fundamental principles and applications of natural gas hydrates. Nature, vol. 426, pp. 353–363.
 Boswell, R. and Collett, T. S. (2011). Current perspectives on gas hydrate resources. Energy & Environmental Science, vol. 4, pp. 1206–1215.
 Sun, Y. H., Li, B., Guo, W., et al. (2014). Comparative analysis of the production trial and numerical simulations of gas production from multilayer hydrate deposits in the Qilian Mountain permafrost. Journal of Natural Gas Science and Engineering, vol. 21, pp. 456–466.
 Moridis, G. J., Collett, T. S., Pooladi-Darvish, M., et al. (2011). Challenges, Uncertainties, and issues facing gas production from gas-hydrate deposits. SPE Reservoir Evaluation & Engineering, vol. 14, pp. 76–112.
 Koh, D. Y., Kang, H., Lee, J. W., et al. (2016). Energy-efficient natural gas hydrate production using gas exchange. Applied Energy, vol. 162, pp. 114–130.
 Ohgaki, K., Takano, K., Sangawa, H., et al. (1996). Methane exploitation by carbon dioxide from gas hydrates-phase equilibria for CO2-CH4 mixed hydrate system. Journal of Chemical Engineering of Japan, vol. 29, pp. 478–483.
 Klapp, S. A., Murshed, M. M., Pape, T., et al. (2010). Mixed gas hydrate structures at the Chapopote Knoll, Southern Gulf of Mexico. Earth and Planetary Science Letters, vol. 299, pp. 207–217.
 Kida, M., Khlystov, O., Zemskaya, T., et al. (2006). Coexistence of structure I and II gas hydrates in Lake Baikal suggesting gas sources from microbial and thermogenic origin. Geophysical Research Letters, vol. 33.
 Zhu, Y. H., Zhang, Y. Q., Wen, H. J., et al. (2010). Gas hydrates in the Qilian Mountain Permafrost, Qinghai, Northwest China. Acta Geologica Sinica-English Edition, vol. 84, pp. 1–10.
 Wei, J., Fang, Y., Lu, H., et al. (2017). Coexistence of SI and SII hydrates in the South China Sea. The Ninth International Conference on Gas Hydrate. Denver, USA.
 Park, Y., Kim, D. Y., Lee, J. W., et al. (2006). Sequestering carbon dioxide into complex structures of naturally occurring gas hydrates. Proceedings of the National Academy of Sciences of the United States of America, vol. 103, pp. 12690–12694.
 Schicks, J. M., Luzi, M., and Beeskow-Strauch, B. (2011). The conversion process of hydrocarbon hydrates into CO2 hydrates and vice versa: thermodynamic considerations. The Journal of Physical Chemistry A, vol. 115, pp. 13324–13331.
 Beeskow-Strauch, B. and Schicks, J. M. (2012). The driving forces of guest substitution in gas hydrates – A laser Raman study on CH4–CO2 exchange in the presence of impurities. Energies, vol. 5, pp. 420–437.
 Seo, Y. J., Park, S., Kang, H., et al. (2016). Isostructural and cage-specific replacement occurring in SII hydrate with external CO2/N2 gas and its implications for natural gasproduction and CO2 storage. Applied Energy, vol. 178, pp. 579–586.
 Lee, Y., Choi, W., Shin, K., et al. (2017). CH4-CO2 replacement occurring in SII natural gas hydrates for CH4 recovery and CO2 sequestration. Energy Conversion and Management, vol. 150, pp. 356–364.
 Sun, Y. H., Su, K., Li, S. L., et al. (2018). Experimental investigation into the dissociation behavior of CH4-C2H6-C3H8 hydrates in sandy sediments by depressurization. Energy & Fuels, vol. 32, pp. 204–213.
 Lee, B. R., Koh, C. A., and Sum, A. K. (2014). Quantitative measurement and mechanisms for CH4 production from hydrates with the injection of liquid CO2. Physical Chemistry Chemical Physics, vol. 16, pp. 14922–14927.
 Zhao, J. F., Zhang, L. X., Chen, X. Q., et al. (2015). Experimental study of conditions for methane hydrate productivity by the CO2 swap method. Energy & Fuels, vol. 29, pp. 6887–6895.
 Yuan, Q., Sun, C. Y., Yang, X., et al. (2012). Recovery of methane from hydrate reservoir with gaseous carbon dioxide using a three-dimensional middle-size reactor. Energy, vol. 40, pp. 47–58.
 Yoon, J. H., Kawamura, T., Yamamoto, Y., et al. (2004). Transformation of methane hydrate to carbon dioxide hydrate: In situ Raman spectroscopic observations. The Journal of Physical Chemistry A, vol. 108, pp. 5057–5059.
 Falenty, A., Qin, J., Salamatin, A. N., et al. (2016). Fluid composition and kinetics of the in situ replacement in CH4-CO2 hydrate system. The Journal of Physical Chemistry C, vol. 120, pp. 27159–27172.
 Kim, H. C., Bishnoi, P. R., Heidemann, R. A., et al. (1987). Kinetics of methane hydrate decomposition. Chemical Engineering Science, vol. 33, pp. 347–350.
 Yousif, M. H., Abass, H. H., Selim, M. S., et al. (1991). Experimental and theoretical investigation of methane-gas-hydrate dissociation in porous media. SPE Reservoir Evaluation & Engineering, vol. 6, pp. 69–76.
 Yousif, M. H., Li, P. M., Selim, M. S., et al. (1990). Depressurization of natural gas hydrates in berea sandstone cores. Journal of Inclusion Phenomena and Macrocyclic Chemistry, vol. 8, pp. 71–88.