Energy Fuels 2009, 23, 5580–5586 Published on Web 09/29/2009
: DOI:10.1021/ef900612f
Characteristics of Natural Gas Hydrates Occurring in Pore-Spaces of Marine Sediments Collected from the Eastern Nankai Trough, off Japan Masato Kida, Kiyofumi Suzuki, Taro Kawamura, Hiroyuki Oyama, Jiro Nagao,* Takao Ebinuma, and Hideo Narita Methane Hydrate Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 2-17-2-1 Tsukisamu-Higashi, Toyohiraku, Sapporo, Hokkaido 062-8517, Japan
Hiroyuki Suzuki Department of Applied Molecular Chemistry, College of Industrial Technology, Nihon University, 1-2-1 Izumicho, Narashino, Chiba 275-8575, Japan
Hirotoshi Sakagami and Nobuo Takahashi Department of Materials Science and Engineering, Kitami Institute of Technology (KIT), 165 Koen-cho, Kitami, Hokkaido 090-8507, Japan Received June 16, 2009. Revised Manuscript Received September 11, 2009
Pore-space gas hydrates sampled from the eastern Nankai Trough area off of Japan were minutely characterized using several instrumental techniques. Gas chromatographic results indicated that the natural gas in the sediment samples studied comprises mainly CH4. The concentrations of minor components varied according to depth. The powder X-ray diffraction patterns showed that the porespace hydrates were of structure I (sI); the lattice constants were 1.183-1.207 nm. Both 13C NMR and Raman spectra confirmed that CH4 molecules were encaged in sI hydrate lattice. The average cage occupancies were calculated, respectively, from the Raman data as 0.83 for small cages and 0.97 for large cages. The hydration numbers were determined as 6.1-6.2. amount, because the gas capacity of hydrate crystals is attributed to the structure. The cage occupancy is defined as a ratio that affects the gas capacity of hydrate crystals: (number of hydrate cages occupied by guest molecules)/(number of total hydrate cages). The hydration number (n) is defined as the number of water molecules per guest molecule, as calculated from the cage occupancies. These parameters can vary according to gas components, which are important for estimates of the natural gas reservoir capacity.8 Powder X-ray diffraction (PXRD) has been used widely to obtain crystallographic information related to the NGH lattice structure.1,3,9-19 The 13C nuclear magnetic resonance (13C NMR) technique has been used not only to identify the
1. Introduction Natural gas hydrates (NGHs), crystalline clathrate compounds that encage large amounts of natural gas, are stable in locations with high pressures and low temperatures such as deep marine/lacustrine or permafrost environments. Actually, NGHs serve a role as natural gas reservoirs; they attract attention from viewpoints of resource development and effects on global climate change. Hydrocarbons of C1-C7 can be encaged in the NGH cages.1-3 Common crystallographic structures of NGHs are structure I (sI), structure II (sII), and structure H (sH).4,5 The crystallographic structure of NGHs depends on the encaged natural gas components,1-3,6,7 which are important to determine in order to support estimation of the natural gas
(8) Kida, M.; Hachikubo, A.; Sakagami, H.; Minami, H.; Krylov, A.; Yamashita, S.; Takahashi, N.; Shoji, H.; Khlystov, O.; Poort, J.; Narita, H. Geochem. Geophys. Geosyst. 2009, 10, Q05003. (9) Tulk, C. A.; Ratcliffe, C. I.; Ripmeester, J. A. Geol. Surv. Can. Bull. 1999, 544, 251–262. (10) Matsumoto, R.; Uchida, T.; Waseda, A.; Uchida, T.; Takeya, S.; Hirano, T.; Yamada, K.; Maeda, Y.; Okui, T. Proc. Ocean Drill. Progr., Sci. Results 2000, 164, 13–28. (11) Yousuf, M.; Qadri, S. B.; Knies, D. L.; Grabowski, K. S.; Coffin, R. B.; Pohlman, J. W. Appl. Phys. A 2004, 78, 925–939. (12) Uchida, T.; Uchida, T.; Kato, A.; Sasaki, H.; Kono, F.; Takeya, S. Geol. Surv. Can. Bull. 2005, 585. (13) Ripmeester, J. A.; Lu, H.; Moudrakovski, I. L.; Dutrisac, R.; Wilson, L. D.; Wright, F.; Dallimore, S. R. Geol. Surv. Can. Bull. 2005, 585, 106. (14) Takeya, S.; Uchida, T.; Kamata, Y.; Nagao, J.; Kida, M.; Minami, H.; Sakagami, H.; Hachikubo, A.; Takahashi, N.; Shoji, H.; Khlystov, O.; Grachev, M.; Soloviev, V. Angew. Chem., Int. Ed. 2005, 44, 6928–6931.
*To whom correspondence should be addressed. Telephone: þ81-(0)11-857-8948. Fax: þ81-(0)11-857-8985. E-mail: jiro.nagao@ aist.go.jp. (1) Davidson, D. W.; Garg, S. K.; Gough, S. R.; Handa, Y. P.; Ratciffe, C. I.; Ripmeester, J. A.; Tse, J. S.; Lawson, W. F. Geochim. Cosmochim. Acta 1986, 50, 619–623. (2) Kida, M.; Khlystov, O.; Zemskaya, T.; Takahashi, N.; Minami, H.; Sakagami, H.; Krylov, A.; Hachikubo, A.; Yamashita, S.; Shoji, H.; Poort, J.; Naudts, L. Geophys. Res. Lett. 2006, 33, L24603. (3) Lu, H.; Seo, Y.-T.; Lee, J.-W.; Moudrakovski, I.; Ripmeester, J. A.; Chapman, N. R.; Coffin, R. B.; Gardner, G.; Pohlman, J. Nature 2007, 445, 303–306. (4) Sloan, E. D., Jr. Energy Fuels 1998, 12, 191–196. (5) Sloan, E. D., Jr. Nature 2003, 426, 353–359. (6) Sassen, R.; MacDonald, I. R. Org. Geochem. 1994, 22, 1029–1032. (7) Uchida, T.; Hirano, T.; Ebinuma, T.; Narita, H.; Gohara, K.; Mae, S.; Matsumoto, R. AIChE J. 1999, 45, 2641–2645. r 2009 American Chemical Society
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Energy Fuels 2009, 23, 5580–5586
: DOI:10.1021/ef900612f
Kida et al.
crystallographic structure of NGHs, but also to clarify cage occupancy by guest molecules and the hydration number of NGHs.1-3,8,9,13-17 Although Raman spectroscopy has also been used to estimate cage occupations and hydration numbers of NGHs,7,9,10,13,15,16 the separation of characteristic Raman bands of encaged molecules can be difficult due to their peak width or heavy overlap in a spectrum, in the case that methane and heavier hydrocarbons coexist. The Nankai Trough is located on the boundary between the Philippine Sea Plate and the Eurasian Plate off of Japan, where NGHs are believed to be widespread.20,21 In late 1999 and early 2000 the research and development project for NGHs in the eastern Nankai Trough area, conducted by the Japanese Ministry of International Trade and Industry (MITI), recovered NGH-bearing sediment cores.22 The gas hydrate crystals were very small in size and existed in intergranular pores of sandy sediments. In some instances, however, the crystals were visible to the naked eye.22 Japan’s Methane Hydrate R&D Program, conducted by the Ministry of Economy, Trade and Industry (METI) of Japan, has been underway at the eastern Nankai Trough area since 2001. Resource assessments of gas hydrates in this area have been attempted using 2D/3D seismic data and drilling survey data.23,24 In this study sediment samples, recovered from the eastern Nankai Trough area, were examined by sediment particle-size distribution analysis, powder X-ray diffraction (PXRD), gas chromatography, 13C nuclear magnetic resonance (13C NMR), and Raman investigations. This is the first released study to elucidate the detailed structural characteristics of natural pore-space gas hydrates recovered from the eastern Nankai Trough area, such as encaged gas components, crystallographic structure, lattice constant, cage occupancies, and hydration number.
Figure 1. Sampling locations in the eastern Nankai Trough area. Table 1. Depths of Sediment Samples Recovered from the Eastern Nankai Trough study area
sample
well
location-A
A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11
a a a b b b c c c c c
location-B
B1 B2 B3
317 319 323
location-C
C1
350
2. Materials and Experimental Methods Sediment samples were recovered from three different areas in the eastern Nankai Trough area denoted as locations A, B, and C. The sediment samples were obtained during Japan’s Methane Hydrate R&D Program conducted by METI in 2004, aboard the RV JOIDES Resolution. The detailed coring locations and descriptions were summarized in a previous report.25 Sediment
depth (mbsf) 153 153 155 160 161 164 167 167 170 173 175
samples were obtained at water depths of 700-2000 m using a pressure-temperature core sampler (PTCS).25 The sampling areas are presented in Figure 1. The map was constructed on the basis of reports from the relevant literature.24 The geographical information of the study areas has been shown in detail in the previous report.24 Sediment samples were stored and transported at liquid N2 temperatures. The sample depths, which were recorded during the core recoveries, are presented in Table 1. The location-A samples were recovered from three different wells (a, b, and c); they are designated as A1-A11 in order of the depth from which they were acquired. Samples A2 and A8 were collected, respectively, from 10 cm below sample A1 in the core unit of 153 m below the sea floor (mbsf) and 10 cm below sample A7 in that of 167 m. Similarly, the location-B and location-C samples were designated, respectively, as B1-B3 and C1. In this study, 15 sediment samples, namely A1-A11, B1-B3, and C1, were studied using the sediment particle size distribution analysis, gas chromatography, and PXRD. Several of these samples were selected for 13C NMR and Raman measurements. The hydrocarbon compositions in gases released from small fractions of the sediment samples at room temperature were measured using a gas chromatograph (model GC-2010; Shimadzu Corp.) equipped with a flame ionization detector with a fused silica capillary column (Quadrex Corp.). After degassing and drying, the sediment particle size distributions were measured
(15) Kim, D.-Y.; Uhm, T.-W.; Lee, H.; Lee, Y.-J.; Ryu, B.-J.; Kim, J.-H. Korean J. Chem. Eng. 2005, 22 (4), 569–572. (16) Lu, H.; Moudrakovski, I.; Riedel, M.; Spence, G.; Dutrisac, R.; Ripmeester, J.; Wright, F.; Dallimore, S. J. Geophys. Res. 2005, 110, B10204. (17) Takeya, S.; Kida, M.; Minami, H.; Sakagami, H.; Hachikubo, A.; Takahashi, N.; Shoji, H.; Soloviev, V.; Wallmann, K.; Biebow, N.; Obzhirov, A.; Salomatin, A.; Poort, J. Chem. Eng. Sci. 2006, 61, 2670– 2674. (18) Bohrmann, G.; Kuhs, W. F.; Klapp, S. A.; Techmer, K. S.; Klein, H.; Murshed, M. M.; Abegg, F. Mar. Geol. 2007, 244, 1–14. (19) Udachin, K. A.; Lu, H.; Enright, G. D.; Ratcliffe, C. I.; Ripmeester, J. A.; Chapman, N. R.; Riedel, M.; Spence, G. Angew. Chem., Int. Ed. 2007, 46, 8220–8222. (20) Satoh, M. Proc. 4th Int. Conf. Gas Hydrates 2002, 175–178. (21) Colwell, F.; Matsumoto, R.; Reed, D. Chem. Geol. 2004, 205, 391–404. (22) Uchida, T.; Lu, H.; Tomaru, H. Resource Geol. 2004, 54, 35–44. (23) Fujii, T.; Saeki, T.; Kobayashi, T.; Inamori, T.; Hayashi, M.; Takano, O.; Takayama, T.; Kawasaki, T.; Nagakubo, S.; Nakamizu, M.; Yokoi, K. Proceedings of 2008 Offshore Technology Conference, Houston, TX, May 2008; OTC19310. (24) Saeki, T.; Fujii, T.; Inamori, T.; Kobayashi, T.; Hayashi, M.; Nagakubo, S.; Takano, O. Proceedings of 2008 Offshore Technology Conference, Houston, TX, May 2008; OTC19311. (25) Takahashi, H.; Tsuji, Y. Proceedings of 2005 Offshore Technology Conference, Houston, TX, May 2005; OTC17162.
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: DOI:10.1021/ef900612f
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Figure 2. Photographs of pieces of typical sediment samples recovered from the eastern Nankai Trough area: location-A (sample A9), location-B (sample B2), and location-C (sample C1). Table 2. Molecular Compositions of Hydrocarbon in Released Gases from Sediment Samples Recovered from the Eastern Nankai Trough Areaa released gas concentration CH4 (%)
C2H6 (ppm)
C3H8 (ppm)
153 153 155 160 161 164 167 167 170 173 175
98.8803 ( 0.0236 99.9363 ( 0.0023 99.9485 ( 0.0052 99.9924 ( 0.0001 99.9937 ( 0.0001 99.9945 ( 0.0001 99.9873 ( 0.0001 99.9860 ( 0.0002 99.9834 ( 0.0001 99.9888 ( 0.0001 99.9888 ( 0.0007
66.9 ( 12.5 41.0 ( 4.3 122.1 ( 7.2 65.1 ( 0.9 59.9 ( 0.9 54.4 ( 0.6 125.4 ( 1.4 126.7 ( 1.2 157.7 ( 0.3 94.1 ( 2.3 83.7 ( 6.3
4960.9 ( 74.6 440.2 ( 11.5 386.7 ( 43.2 10.9 ( 0.3 2.4 ( 0.6
