高圧力の科学と技術

特集－ガスハイドレート－

ガスハイドレートの高圧物性

清水宏晏

原稿種別: 解説
専門分野: 高圧科学
2002 年 12 巻 1 号 p. 3-9
発行日: 2002年
公開日: 2003/06/17

DOIhttps://doi.org/10.4131/jshpreview.12.3

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The fundamental properties of gas hydrates are reviewed; classification and type, structure and composition, formation and stability, and occupancy of guest molecules. Recent Raman studies on the properties of cage-occupancy are discussed by considering the C-H vibrations of their guest molecules for methane, methane-ethane mixed (structural phase transition), ethane, and cyclopropane (pressure-induced small cage occupancy) hydrates. Finally, I give an overview of very recent x-ray (neutron) diffraction and Raman scattering studies of phase transitions in the methane hydrate at high pressures, and discuss the inconsistent results by investigating the experimental details.

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特異な条件下でのガスハイドレートの形成

¹²⁹Xe NMR によるキャラクタリゼーション

中山尋量, 尾身洋典, 江口太郎, Denis D. KLUG, John S. TSE, Chris I. RATCLIFFE, J ...

原稿種別: 解説
専門分野: 高圧科学
2002 年 12 巻 1 号 p. 10-15
発行日: 2002年
公開日: 2003/06/17

DOIhttps://doi.org/10.4131/jshpreview.12.10

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In this article, recent research works on the formation process of gas hydrate were reviewed. We describe how efficiently a solid-state ¹²⁹Xe NMR technique was applied to monitor the formation processes of gas hydrates, together with a short review of ¹²⁹Xe NMR. Especially, the formation process from an amorphous mixture of Xe and H₂O was described precisely.

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高圧ブリュアン散乱によるメタンハイドレートの弾性的性質

佐々木重雄, 熊崎達也, 久米徹二, 清水宏晏

原稿種別: 解説
専門分野: 高圧科学
2002 年 12 巻 1 号 p. 16-21
発行日: 2002年
公開日: 2003/06/17

DOIhttps://doi.org/10.4131/jshpreview.12.16

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The elastic properties of structure I (sI) methane hydrate (MH) determined by high-pressure Brillouin spectroscopy up to 0.6 GPa at 23°C are reviewed by comparing them with those of ice-Ih. The pressure dependence of adiabatic elastic moduli of sI-MH is similar to that of ice-Ih except for C₁₁. Elastic moduli and bulk modulus indicate that sI-MH is slightly more compressive than ice-Ih, and acoustic velocities show nearly isotropic behaviors with respect to the crystal orientation. The C₄₄ of sI-MH is less sensitive to pressure and smaller than C₁₁ and C₁₂, which implies the sI-MH is becoming less stable against the shear stress under high pressures. These results are useful to investigate the dynamic stability and the estimated amount of MH in the deep-sea sediments.

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ハイドレート中の分子間相互作用とダイナミクス

竹林良浩, 大竹勝人

原稿種別: 解説
専門分野: 高圧科学
2002 年 12 巻 1 号 p. 22-27
発行日: 2002年
公開日: 2003/06/17

DOIhttps://doi.org/10.4131/jshpreview.12.22

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The guest-host interactions and the rotational dynamics in the clathrate hydrates of acetone and THF are discussed in comparison with those in the supercooled aqueous solutions by measuring the ¹³C NMR chemical shift and the ²D spin-lattice relaxation time as functions of the temperature. When the temperature is decreased, the guest-water hydrogen bond is discontinuously reduced upon the clathrate cage formation. Due to the reduced friction with surrounding waters, the guest molecule reorients much faster in the clathrate cage than in the aqueous solution. On the other hand, the remaining guest-water interaction fluctuates the reorientational motion of the cage water. We also review the structural similarity between the clathrate hydrate and the aqueous solution.

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メタンハイドレートの高圧相転移

平井寿子, 内原弓佳子

原稿種別: 解説
専門分野: 高圧科学
2002 年 12 巻 1 号 p. 28-33
発行日: 2002年
公開日: 2003/06/17

DOIhttps://doi.org/10.4131/jshpreview.12.28

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Recent high-pressure studies using diamond anvil cell of methane hydrate are reviewed. Three high-pressure phases of methane hydrate were observed by x-ray diffraction and Raman spectroscopy up to 8 GPa in the present authors' study. The well-known cubic phase I decomposed into a hexagonal phase A and fluid at 0.8 GPa. The phase A transformed into an orthorhombic phase B at 1.6 GPa, and the phase B further transformed into another orthorhombic phase C at 2.1 GPa which survived above 7.8 GPa. The fluid solidified as ice VI at 1.4 GPa, and the ice VI transformed to ice VII at 2.1 GPa. The bulk moduli, K₀, for the phase I, phase A, and phase C were calculated to be 7.4, 9.8, and 25.0 GPa, respectively. Comparison of the highpressure studies and the description of these high pressure structures were described in detail.

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純粋ならびに混合ガスハイドレートの相平衡関係

菅原武, 菅原啓祐, 大垣一成

原稿種別: 解説
専門分野: 高圧科学
2002 年 12 巻 1 号 p. 34-39
発行日: 2002年
公開日: 2003/06/17

DOIhttps://doi.org/10.4131/jshpreview.12.34

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As a fundamental study of gas hydrates, which are key substances in the energy and environmental problems, the thermodynamic stability for the pure and mixed gas hydrate systems is investigated. The intermolecular vibration energy between the host water molecules and the intramolecular vibration energies of guest species are measured by means of laser Raman spectroscopy. The structural phase transition controlled on the equilibrium composition of the mixed gas is observed in the (methane + ethylene) mixed gas hydrate systems, while each pure hydrate has no structural phase transition in the whole range in this study.

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CO₂海洋隔離とCO₂ハイドレート

綾威雄, 山根健次, 小島隆志, 波江貞弘

原稿種別: 解説
専門分野: 高圧科学
2002 年 12 巻 1 号 p. 40-49
発行日: 2002年
公開日: 2003/06/17

DOIhttps://doi.org/10.4131/jshpreview.12.40

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CO₂ ocean sequestration, which is thought to be a promising measure to mitigate global warming, can be classified mainly into the dissolution and the storage methods. On the evaluation of these measures, CO₂ hydrate plays an important role, because CO₂ becomes a hydrate in the ocean deeper than 500 m (North Pacific Ocean)∼900 m (North Atlantic Ocean). The solubility of CO₂ shows a dual nature (solid and liquid solubilities) in the hydrate forming region. Two types of unexpected hydrate membrane strength just below the dissociation temperature and in a CO₂ saturated solution, and the rebuilding process under stressed conditions greatly influence the above two CO₂ ocean sequestration methods.

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メタンハイドレート層の掘削

－基礎試錐「南海トラフ」掘削実績－

若月基, 米澤哲夫, 高橋秀明, 武富義和

原稿種別: 解説
専門分野: 高圧科学
2002 年 12 巻 1 号 p. 50-55
発行日: 2002年
公開日: 2003/06/17

DOIhttps://doi.org/10.4131/jshpreview.12.50

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Exploration for natural methane hydrate was carried out in the Nankai-Trough offshore Japan at a water depth of 945 m over an 88-day period, from November 1999 to February 2000. This was a national project led by the Ministry of International Trade and Industry (MITI) to seek a new energy source. It was organized by Japan National Oil Corporation (JNOC) in collaboration with Japan Petroleum Exploration Co., Ltd. as the drilling operator. The Nankai-Trough wells were drilled with a deepwater semisubmersible rig. The location was selected where BSR (Bottom Simulating Reflector) is the clearest on the seismic section. Six wells were drilled through the BSR horizon and the hydrate rich formation was confirmed between 1135 m to 1213 m BMSL (below mean sea level) by LWD data, core samples and electric logging data.

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CO₂によるメタンハイドレート中のメタンの置換速度

乗京逸夫, 川村和茂, 村椿良司

原稿種別: 解説
専門分野: 高圧科学
2002 年 12 巻 1 号 p. 56-61
発行日: 2002年
公開日: 2003/06/17

DOIhttps://doi.org/10.4131/jshpreview.12.56

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Injection of liquid CO₂ in hydrate layers of natural gas is a promising technique to recover methane simultaneously segregating CO₂ from the biosphere. This work examined the rate of the conversion of CH₄-hydrate immersed in liquid CO₂ to CO₂-hydrate in a temperature range of 274-281 K and a pressure range of 4-10 MPa. About 17% of the methane, utilizing CO₂, was recovered after 300 hours at 10 MPa and 281 K, and the conversion was on going even at the end of every experiment. The solute mobility rose as the temperature increased; it decreased as the total pressure increased. The solute mobility of methane and CO₂ in hydrate solid was determined for future feasibility studies. The configuration of the system should be investigated in a feasibility study, including the recovery system for CH₄.

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技術シリーズ「圧力スケール」 (1)

メガバール領域でのPtとAu圧力スケールのクロスチェックとBiの状態方程式

赤浜裕一, 川村春樹, Anil K. SINGH

原稿種別: 解説
専門分野: 高圧技術
2002 年 12 巻 1 号 p. 63-68
発行日: 2002年
公開日: 2003/06/17

DOIhttps://doi.org/10.4131/jshpreview.12.63

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The volume compression of Bi, Pt and Au has been measured to megabar pressures by x-ray powder-diffraction experiments using a synchrotron radiation source. The EOS's of Pt and Au as the pressure scale have been crosschecked up to 145 GPa, and a considerable inconsistency between them is revealed in the megabar pressure region. The EOS of Au has been determined up to the megabar pressure range by the Pt scale. Stability of the high-pressure bcc phase of Bi is confirmed up to 222 GPa. The equation of state (EOS) of bcc-Bi is determined in a megabar pressure range with the bulk modulus, B₀ = 35.45(26) GPa, its pressure derivative, B₀' = 6.294(32) and the relative atomic volume, V/V₀ = 0.8927(8) at atmospheric pressure, respectively.

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