Angelo Lucia

Jae W. Lee

Costas Tsouris

Advances in Gas Hydrate Thermodynamics and Transport Properties

A new method implementing molecular dynamics (MD) simulations for calculating the reference properties of simple gas hydrates has been proposed. The guest molecules affect interaction between adjacent water molecules distorting the hydrate lattice, which requires diverse values of reference properties for different gas hydrates. We performed simulations to validate the experimental data for determining <svg style="vertical-align:-3.21404pt;width:30.025px;" id="M1" height="17.775" version="1.1" viewBox="0 0 30.025 17.775" width="30.025"  xmlns="http://www.w3.org/2000/svg">
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</svg>, the chemical potential difference between water and theoretical empty cavity at the reference state, for structure II type gas hydrates. Simulations have also been used to observe the variation of the hydrate unit cell volume with temperature. All simulations were performed using TIP4P water molecules at the reference temperature and pressure conditions. The values were close to the experimental values obtained by the Lee-Holder model, considering lattice distortion.

Krishnadeo Jatkar

Sangyong Lee

Determination of Reference Chemical Potential Using Molecular Dynamics Simulations

An experimental study of the dissociation of methane hydrate (MH) by hot-water injection and depressurization was carried out at the National Institute of Advanced Industrial Science and Technology (AIST). These experiments helped us understand some important aspects of MH behavior such as how temperature, pressure, and permeability change during dissociation and gas production. In order to understand the experimental results, a model of MH dissociation in a porous media was designed and implemented in a numerical simulator. In the model, we treated the MH phase as a two-component system by representing the pore space occupied by MH as a separate component. Absolute permeability and relative permeability were formulated as a function of MH saturation, porosity, and sand grain diameter and introduced into the numerical model. Using the developed numerical simulator, we attempted history matching of laboratory-scale experiments of the MH dissociation process. It was found that numerical simulator was able to reproduce temperature change, permeability characteristics, and gas production behavior associated with both MH formation and dissociation.

Yasuhide Sakamoto

Takeshi Komai

Kuniyuki Miyazaki

Norio Tenma

Tsutomu Yamaguchi

George Zyvoloski

Laboratory-Scale Experiments of the Methane Hydrate Dissociation Process in a Porous Media and Numerical Study for the Estimation of Permeability in Methane Hydrate Reservoir

We propose several physical/chemical causes to support the seismic results which find presence of Bottom Simulating Reflector (BSR) at site 1144 and site 1148 in Dongsha Region, North of South China Sea. At site 1144, according to geothermal gradient, the bottom of stability zone of conduction mode is in agreement with BSR. At site 1148, however, the stability zone of conduction mode is smaller than the natural gas presence zone predicted by the BSR. We propose three causes, that is, mixed convection and conduction thermal flow mode, multiple composition of natural gas and overpressure in deep sediment to explain the BSR presence or gas hydrate presence. Further, our numerical simulation results suggest yet another reason for the presence of BSR at site 1144 and site 1148. Because the temperatures in deep sediment calculated from the mixed convection and conduction thermal flow mode are lower than that from the single conduction mode, the bottom of gas hydrate stability zone (GHSZ) is deeper than the bottom of gas hydrate deposition zone (GHDZ) or BSR. The result indicates that occurrence zone of natural is decided by the condition that natural gas concentrate in the zone is greater than its solubility.

Zuan Chen

Wuming Bai

Wenyue Xu

Zhihe Jin

An Analysis on Stability and Deposition Zones of Natural Gas Hydrate in Dongsha Region, North of South China Sea

Differential scanning calorimetry was used to study the effect of isotopic substitution on the eutectic and melting temperatures in the water-tetrahydrofuran (THF) system with THF molar fractions near the stoichiometry of the hydrate phase. Deuteration of the host causes an opposite effect from that of the guest with respect to the hydrate liquidus curve and eutectic melting temperature. The eutectic temperature in <svg     style="vertical-align:-3.27605pt;width:31.65px;" id="M1" height="15.5125" version="1.1" viewBox="0 0 31.65 15.5125" width="31.65"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
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</svg>-containing systems is approximately 3.7&#x2009;K higher than that in <svg     style="vertical-align:-3.27605pt;width:32.174999px;" id="M2" height="15.5125" version="1.1" viewBox="0 0 32.174999 15.5125" width="32.174999"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
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</svg>-containing systems. The melting temperatures of THF and deuterated THF hydrates increase by roughly 3.5&#x2009;K with heavy water. The inclusion of deuterated THF causes a depression of the hydrate liquidus temperatures and a small but measurable effect on the eutectic temperature.

C. Y. Jones

J. S. Zhang

J. W. Lee

Isotope Effect on Eutectic and Hydrate Melting Temperatures in the Water-THF System

Methane gas hydrates in sediments have been studied by several investigators as a possible future energy resource. Recent hydrate reserves have been estimated at approximately <svg style="vertical-align:-0.1638pt;width:28.487499px;" id="M1" height="16.112499" version="1.1" viewBox="0 0 28.487499 16.112499" width="28.487499" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,15.85)"><path id="x31" d="M384 0h-275v27q67 5 81.5 18.5t14.5 68.5v385q0 38 -7.5 47.5t-40.5 10.5l-48 2v24q85 15 178 52v-521q0 -55 14.5 -68.5t82.5 -18.5v-27z" /></g><g transform="matrix(.017,-0,0,-.017,8.222,15.85)"><path id="x30" d="M241 635q53 0 94 -28.5t63.5 -76t33.5 -102.5t11 -116q0 -58 -11 -112.5t-34 -103.5t-63.5 -78.5t-94.5 -29.5t-95 28t-64.5 75t-34.5 102.5t-11 118.5q0 58 11.5 112.5t34.5 103t64.5 78t95.5 29.5zM238 602q-32 0 -55.5 -25t-35.5 -68t-17.5 -91t-5.5 -105&#xA;q0 -76 10 -138.5t37 -107.5t69 -45q32 0 55.5 25t35.5 68.5t17.5 91.5t5.5 105t-5.5 105.5t-18 92t-36 68t-56.5 24.5z" /></g><g transform="matrix(.012,-0,0,-.012,16.375,7.688)"><use xlink:href="#x31" /></g><g transform="matrix(.012,-0,0,-.012,22.086,7.688)"><path id="x36" d="M137 343l67 33q37 17 63 17q79 0 129.5 -53t50.5 -131q0 -92 -58 -156.5t-147 -64.5t-147 68t-58 182q0 63 17 119t43 95.5t61.5 72t69 52t67.5 31.5q62 22 128 33l6 -32q-56 -11 -108 -35q-149 -71 -184 -231zM227 337q-47 0 -95 -27q-6 -23 -6 -70q0 -93 36 -155.5&#xA;t96 -62.5q53 0 78 45.5t25 105.5q0 68 -35 116t-99 48z" /></g></svg> <svg style="vertical-align:-0.0pt;width:20.375px;" id="M2" height="15.8375" version="1.1" viewBox="0 0 20.375 15.8375" width="20.375" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,15.775)"><path id="x6D" d="M797 0h-214v26q46 5 58 17.5t12 63.5v167q0 116 -88 116q-48 0 -112 -52q3 -18 3 -42v-195q0 -46 11 -58t53 -17v-26h-214v26q48 5 59.5 17t11.5 60v172q0 115 -88 115q-47 0 -109 -52v-235q0 -47 10 -59.5t48 -17.5v-26h-211v26q50 5 62.5 17t12.5 60v207q0 48 -9 59.5&#xA;t-52 18.5v23q79 14 139 41v-81q3 2 29 20.5t44 29.5q45 28 81 28t66 -22t46 -61q25 20 83 57q39 26 76 26q59 0 93 -40t34 -113v-193q0 -49 10.5 -60.5t54.5 -16.5v-26z" /></g><g transform="matrix(.012,-0,0,-.012,13.987,7.613)"><path id="x33" d="M285 378v-2q65 -13 102 -54.5t37 -97.5q0 -57 -30.5 -104.5t-74 -75t-85.5 -42t-72 -14.5q-31 0 -59.5 11t-40.5 23q-19 18 -16 36q1 16 23 33q13 10 24 0q58 -51 124 -51q55 0 88 40t33 112q0 64 -39 96.5t-88 32.5q-29 0 -64 -11l-6 29q77 25 118 57.5t41 84.5&#xA;q0 45 -26.5 69.5t-68.5 24.5q-67 0 -120 -79l-20 20l43 63q51 56 127 56h1q66 0 107 -37t41 -95q0 -42 -31 -71q-22 -23 -68 -54z" /></g></svg> of methane gas worldwide at standard temperature and pressure conditions. In situ dissociation of natural gas hydrate is necessary in order to commercially exploit the resource from the natural-gas-hydrate-bearing sediment. The presence of gas hydrates in sediments dramatically alters some of the normal physical properties of the sediment. These changes can be detected by field measurements and by down-hole logs. An understanding of the physical properties of hydrate-bearing sediments is necessary for interpretation of geophysical data collected in field settings, borehole, and slope stability analyses; reservoir simulation; and production models. This work reviews information available in literature related to the physical properties of sediments containing gas hydrates. A brief review of the physical properties of bulk gas hydrates is included. Detection methods, morphology, and relevant physical properties of gas-hydrate-bearing sediments are also discussed.

Jorge F. Gabitto

Physical Properties of Gas Hydrates: A Review

Structure II clathrate hydrates of pure hydrogen and binary hydrates of <svg style="vertical-align:-3.13504pt;width:64.675003px;" id="M3" height="14.375" version="1.1" viewBox="0 0 64.675003 14.375" width="64.675003"  xmlns="http://www.w3.org/2000/svg">
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</svg> are studied using <i  >ab initio</i> calculations to determine the stable occupancies of small cavities. <i  >Ab initio</i> calculations are carried out for a double cavity consisting of one dodecahedron (small cavity) and one hexakaidecahedron (large cavity). These two cavities are attached to each other as in sII hydrates to form a double cavity. One or two <svg style="vertical-align:-3.13504pt;width:17.5px;" id="M4" height="14.375" version="1.1" viewBox="0 0 17.5 14.375" width="17.5"  xmlns="http://www.w3.org/2000/svg">
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</svg> molecules are placed in the small cavity and one THF (or 4<svg style="vertical-align:-3.13504pt;width:17.5px;" id="M5" height="14.375" version="1.1" viewBox="0 0 17.5 14.375" width="17.5"  xmlns="http://www.w3.org/2000/svg">
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</svg> molecules) molecule is placed in the large cavity. We have determined the binding energies of the double cavities at the MP2 level using various basis sets (3-21G, 3-21G(2p), 3-21<svg style="vertical-align:-0.51414pt;width:10.825px;" id="M6" height="9.3125" version="1.1" viewBox="0 0 10.825 9.3125" width="10.825"  xmlns="http://www.w3.org/2000/svg">
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</svg>G(2p)). Different basis sets yield different stable occupancies of the small cavity. The results from the highest basis set (6-31<svg style="vertical-align:-0.51414pt;width:10.825px;" id="M10" height="9.3125" version="1.1" viewBox="0 0 10.825 9.3125" width="10.825"  xmlns="http://www.w3.org/2000/svg">
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</svg>G(2p) with zero point energy corrections) indicate that the single occupancy is slightly more favorable than the double occupancy in both the cases of pure <svg style="vertical-align:-3.13504pt;width:17.5px;" id="M12" height="14.375" version="1.1" viewBox="0 0 17.5 14.375" width="17.5"  xmlns="http://www.w3.org/2000/svg">
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</svg> hydrates and THF + <svg style="vertical-align:-3.13504pt;width:17.5px;" id="M13" height="14.375" version="1.1" viewBox="0 0 17.5 14.375" width="17.5"  xmlns="http://www.w3.org/2000/svg">
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Prasad Yedlapalli

Stable Occupancy of Hydrogen Molecules in <svg style="vertical-align:-3.27605pt" height="15.25" version="1.1" viewBox="0 0 19.475 15.25" width="19.475" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,11.112)"><path id="x48" d="M729 650v-28q-62 -5 -76 -19.5t-14 -75.5v-404q0 -62 13.5 -76t75.5 -19v-28h-268v28q65 5 79.5 19t14.5 76v199h-341v-199q0 -62 14 -76t76 -19v-28h-263v28q61 5 74.5 19t13.5 76v404q0 62 -14 76t-76 19v28h259v-28q-58 -5 -71 -19t-13 -76v-162h341v162&#xA;q0 61 -13.5 75.5t-72.5 19.5v28h261z" /></g><g transform="matrix(.012,-0,0,-.012,13.087,15.187)"><path id="x32" d="M412 140l28 -9q0 -2 -35 -131h-373v23q112 112 161 170q59 70 92 127t33 115q0 63 -31 98t-86 35q-75 0 -137 -93l-22 20l57 81q55 59 135 59q69 0 118.5 -46.5t49.5 -122.5q0 -62 -29.5 -114t-102.5 -130l-141 -149h186q42 0 58.5 10.5t38.5 56.5z" /></g></svg> Clathrate Hydrates and <svg style="vertical-align:-3.27605pt" height="15.25" version="1.1" viewBox="0 0 19.475 15.25" width="19.475" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,11.112)"><path id="x48" d="M729 650v-28q-62 -5 -76 -19.5t-14 -75.5v-404q0 -62 13.5 -76t75.5 -19v-28h-268v28q65 5 79.5 19t14.5 76v199h-341v-199q0 -62 14 -76t76 -19v-28h-263v28q61 5 74.5 19t13.5 76v404q0 62 -14 76t-76 19v28h259v-28q-58 -5 -71 -19t-13 -76v-162h341v162&#xA;q0 61 -13.5 75.5t-72.5 19.5v28h261z" /></g><g transform="matrix(.012,-0,0,-.012,13.087,15.187)"><path id="x32" d="M412 140l28 -9q0 -2 -35 -131h-373v23q112 112 161 170q59 70 92 127t33 115q0 63 -31 98t-86 35q-75 0 -137 -93l-22 20l57 81q55 59 135 59q69 0 118.5 -46.5t49.5 -122.5q0 -62 -29.5 -114t-102.5 -130l-141 -149h186q42 0 58.5 10.5t38.5 56.5z" /></g></svg> + THF Clathrate Hydrates Determined by <i>Ab Initio</i> Calculations

Thermodynamic stability and hydrogen occupancy on the hydrogen + tetra-<svg     style="vertical-align:-0.1638pt;width:8.6625004px;" id="M2" height="7.9499998" version="1.1" viewBox="0 0 8.6625004 7.9499998" width="8.6625004"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
			<g transform="matrix(.017,-0,0,-.017,.062,7.675)"><use xlink:href="#x1D45B"/></g>

		
	
</svg>-butyl ammonium bromide semi-clathrate hydrate were investigated by means of Raman spectroscopic and phase equilibrium measurements under the three-phase equilibrium condition. The structure of mixed gas hydrates changes from tetragonal to another structure around 95&#x2009;MPa and 292&#x2009;K depending on surrounding hydrogen fugacity. The occupied amount of hydrogen in the semi-clathrate hydrate increases significantly associated with the structural transition. Tetra-<svg     style="vertical-align:-0.1638pt;width:8.6625004px;" id="M3" height="7.9499998" version="1.1" viewBox="0 0 8.6625004 7.9499998" width="8.6625004"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
			<g transform="matrix(.017,-0,0,-.017,.062,7.675)"><use xlink:href="#x1D45B"/></g>

		
	
</svg>-butyl ammonium bromide semi-clathrate hydrates can absorb hydrogen molecules by a pressure-swing without destroying the hydrogen bonds of hydrate cages at 15&#x2009;MPa or over.

Shunsuke Hashimoto

Takaaki Tsuda

Kyohei Ogata

Takeshi Sugahara

Yoshiro Inoue

Kazunari Ohgaki

Thermodynamic Properties of Hydrogen + Tetra-<svg style="vertical-align:-0.1638pt" height="7.9499998" version="1.1" viewBox="0 0 8.6625004 7.9499998" width="8.6625004" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,7.675)"><path id="x1D45B" d="M495 86q-46 -47 -87 -72.5t-63 -25.5q-43 0 -16 107l49 210q7 34 8 50.5t-3 21t-13 4.5q-35 0 -109.5 -72.5t-115.5 -140.5q-21 -75 -38 -159q-50 -10 -76 -21l-6 8l84 340q8 35 -4 35q-17 0 -67 -46l-15 26q44 44 85.5 70.5t64.5 26.5q35 0 10 -103l-24 -98h2&#xA;q42 56 97 103.5t96 71.5q46 26 74 26q9 0 16 -2.5t14 -11.5t9.5 -24.5t-1 -44t-13.5 -68.5q-30 -117 -47 -200q-4 -19 -3.5 -25t6.5 -6q21 0 70 48z" /></g></svg>-Butyl Ammonium Bromide Semi-Clathrate Hydrate

This paper presents a radically new approach to cubic equations of state (EOS) in which the Gibbs-Helmholtz equation is used to constrain the attraction or energy parameter, <i>a.</i> The resulting expressions for <svg style="vertical-align:-2.29482pt;width:41.125px;" id="M1" height="13.55" version="1.1" viewBox="0 0 41.125 13.55" width="41.125"  xmlns="http://www.w3.org/2000/svg">
	<g transform="matrix(1.25,0,0,-1.25,0,13.55)">
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			<text transform="matrix(1,0,0,-1,-71.95,63.5)">
				<tspan style="font-size: 12.50px; " x="0" y="0">𝑎</tspan>
				<tspan style="font-size: 12.50px; " x="6.2765059" y="0">(</tspan>
				<tspan style="font-size: 12.50px; " x="10.440005" y="0">𝑇</tspan>
				<tspan style="font-size: 12.50px; " x="17.316654" y="0">,</tspan>
				<tspan style="font-size: 12.50px; " x="22.517902" y="0">𝑝</tspan>
				<tspan style="font-size: 12.50px; " x="28.63187" y="0">)</tspan>
			</text>

		</g>
	</g>
</svg> for pure components and <svg style="vertical-align:-2.29482pt;width:56.237499px;" id="M2" height="13.55" version="1.1" viewBox="0 0 56.237499 13.55" width="56.237499"  xmlns="http://www.w3.org/2000/svg">
	<g transform="matrix(1.25,0,0,-1.25,0,13.55)">
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				<tspan style="font-size: 12.50px; " x="0" y="0">𝑎</tspan>
				<tspan style="font-size: 12.50px; " x="6.2765059" y="0">(</tspan>
				<tspan style="font-size: 12.50px; " x="10.440005" y="0">𝑇</tspan>
				<tspan style="font-size: 12.50px; " x="17.316654" y="0">,</tspan>
				<tspan style="font-size: 12.50px; " x="22.517902" y="0">𝑝</tspan>
				<tspan style="font-size: 12.50px; " x="28.63187" y="0">,</tspan>
				<tspan style="font-size: 12.50px; " x="33.845619" y="0">𝑥</tspan>
				<tspan style="font-size: 12.50px; " x="40.722271" y="0">)</tspan>
			</text>

		</g>
	</g>
</svg> for mixtures contain internal energy departure functions and completely avoid the need to use empirical expressions like the Soave alpha function. Our approach also provides a novel and thermodynamically rigorous mixing rule for <svg style="vertical-align:-2.29482pt;width:56.237499px;" id="M3" height="13.55" version="1.1" viewBox="0 0 56.237499 13.55" width="56.237499"  xmlns="http://www.w3.org/2000/svg">
	<g transform="matrix(1.25,0,0,-1.25,0,13.55)">
		<g transform="translate(72,-61.16)">
			<text transform="matrix(1,0,0,-1,-71.95,63.5)">
				<tspan style="font-size: 12.50px; " x="0" y="0">𝑎</tspan>
				<tspan style="font-size: 12.50px; " x="6.2765059" y="0">(</tspan>
				<tspan style="font-size: 12.50px; " x="10.440005" y="0">𝑇</tspan>
				<tspan style="font-size: 12.50px; " x="17.316654" y="0">,</tspan>
				<tspan style="font-size: 12.50px; " x="22.517902" y="0">𝑝</tspan>
				<tspan style="font-size: 12.50px; " x="28.63187" y="0">,</tspan>
				<tspan style="font-size: 12.50px; " x="33.845619" y="0">𝑥</tspan>
				<tspan style="font-size: 12.50px; " x="40.722271" y="0">)</tspan>
			</text>

		</g>
	</g>
</svg>. When the internal energy departure function is computed using Monte Carlo or molecular dynamics simulations as a function of current bulk phase conditions, the resulting EOS is a multiscale equation of state. The proposed new Gibbs-Helmholtz constrained (GHC) cubic equation of state is used to predict liquid densities at high pressure and validated using experimental data from literature. Numerical results clearly show that the GHC EOS provides fast and accurate computation of liquid densities at high pressure, which are needed in the determination of gas hydrate equilibria.

A MultiScale Gibbs-Helmholtz Constrained Cubic  Equation of State

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