Experimental Research on Dissociation Kinetics of Different Gas Hydrates

Abstract

Abstract:

To improve our understanding of natural gas hydrates dissociation characteristics under vacuum pressure, preliminary experimental studies on the decomposition of synthetic hydrates including methane hydrates, ethane hydrates, propane hydrates, normal butanenitrogen hydrates, iso-butane hydrates, mixed gas hydrates, methane hydrates in various size grained porous media, and natural hydrates recovered from Shenhu sea area in South China Sea and Qilian Mountain permafrost, were conducted in a vacuum device placed in a constant temperature room. The experimental results reveal that except propane hydrates and iso-butane hydrates, the decomposition processes of synthetic methane hydrates, ethane hydrates, normal butanenitrogen hydrates and mixed gas hydrates are similar, and the pressures of the decomposing gases appear monotonically increasing at vacuum condition; however, during the dissociation processes of synthetic methane gas hydrates in porous media, the increasing rate of the decomposing gases pressures generally show “fast-slow-fast” feature and the peculiarity of gas hydrates self-preservation are obvious; similarly, natural hydrates recovered from Shenhu sea area in South China Sea and Qilian Mountain permafrost also reveal apparent selfpreservation during the dissociation processes，but different from natural hydrates Qilian Mountain permafrost, the decomposing gases pressures of natural hydrates recovered from Shenhu sea area increase in a ladder form. The differences between both natural hydrates may be due to different distribution models and occurrences of hydrates in the cores.

Key words: natural gas hydrate, Shenhu sea area, Qilian Mountain permafrost, dissociation kinetics, self-preservation

CLC Number:

P744.4

MENG Qing-Guo, LIU Chang-Ling, YE Yu-Guang, HU Gao-Wei. Experimental Research on Dissociation Kinetics of Different Gas Hydrates[J]. Geoscience, 2010, 24(3): 607-613.

References

[1]Sloan E D. Clathrate Hydrates of Natural Gases ［M］. 2nd ed. New York: Marcel Dekker, 1998：223-224.

[2]林微, 陈光进. 气体水合物分解动力学研究现状［J］. 过程工程学报, 2004, 4(1): 69-74.

[3]Mattew A C, Bishnoi P R. Determination of the intrinsic rate constant and activation energy of CO2 gas hydrate formation using insitu particle size analysis ［J］. Chemical Engineering Science, 2004, 59(14): 2983-2993.

[4]Matthew A C, Bishnoi P R. Determination of the intrinsic rate of ethane gas hydrate decomposition ［J］. Chemical Engineering Science, 2000, 55(21): 4869-4883.

[5]Falenty A, Werner F K. The formation and decomposition kinetics of gas hydrates at subzero temperatures［M］. Vancouver: Proceedings of the 6th International Conference on Gas Hydrates,2008: 1-47.

[6]Liu C L, Lu H L, Ye Y G, et al. Raman spectroscopic observations on the structural characteristics and dissociation behavior of methane hydrates synthesized in silica sands with various sizes ［J］. Energy Fuels, 2008, 22 (6): 3986-3988.

[7]Chuang J, Goodarz A, Duane H S. Natural gas production from hydrate decomposition by depressurization ［J］. Chemical Engineering Science, 2001, 56(20): 5801-5814.

[8]Naval G, Michael W, Subhash S. Analytical modeling of gas recovery from in situ hydrate dissociation ［J］. Journal of Petroleum Science and Engineering, 2001, 29(2): 115-127.

[9]Makogon Y F. Natural gas hydrates:A promising source of energy ［J］. Journal of Natural Gas Science and Engineering, 2010, 2(1):49-59.

[10]吴能友, 梁金强, 王宏斌, 等. 海洋天然气水合物成藏系统研究进展［J］. 现代地质, 2008, 22(3): 356-362.

[11]祝有海, 张永勤, 文怀军, 等. 青海祁连山冻土区发现天然气水合物［J］. 地质学报, 2009, 83(11): 1762-1771.

[12]周锡堂, 陶鲜花, 庞重军. 天然气水合物分解动力学研究进展［J］. 天然气化工, 2006, 31(5): 70-73.

[13]吴时国, 董冬冬, 杨胜雄, 等. 南海北部陆坡细粒沉积物天然气水合物系统的形成模式初探［J］. 地球物理学报, 2009, 52(7): 1849-1857.

[14]吴能友, 张海啟, 杨胜雄, 等. 南海神狐海域天然气水合物成藏系统初探［J］. 天然气工业, 2007, 27 (9): 1-6.

[15]龚建明, 胡学平, 王文娟, 等. 南海神狐海域X区块天然气水合物的控制因素［J］. 现代地质, 2009, 23(6): 1131-1137.

[16]John J C. Natural Gas Hydrates: A Guide for Engineers ［M］. Amsterdam：Gulf Professional, 2003：22.

[17]展静, 吴青柏, 蒋观利. 冰颗粒粒径对冰点以下甲烷水合物自保护效应的影响［J］. 天然气地球科学, 2008, 19(4): 577-580.

[18]丁丽颖, 耿春宇, 赵月红, 等. 甲烷水合物分解及自保护效应的分子动力学模拟［J］. 中国科学：B辑, 2008, 38(2): 161-169.