Nonequilibrium Thermodynamics of Hydrate Growth on a Gas-Liquid Interface

• Published in: Physical Review Letters
• Main Authors: Fu, Xiaojing, Cueto-Felgueroso, Luis, Juanes, Ruben
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Physical Society 2018
• Subjects: Methane hydrate
• Online Access: https://doi.org/10.1103/physrevlett.120.144501

We develop a continuum-scale phase-field model to study gas-liquid-hydrate systems far from thermodynamic equilibrium. We design a Gibbs free energy functional for methane-water mixtures that recovers the isobaric temperature-composition phase diagram under thermodynamic equilibrium conditions. The proposed free energy is incorporated into a phase-field model to study the dynamics of hydrate formation on a gas-liquid interface. We elucidate the role of initial aqueous concentration in determining the direction of hydrate growth at the interface, in agreement with experimental observations. Our model also reveals two stages of hydrate growth at an interface—controlled by a crossover in how methane is supplied from the gas and liquid phases—which could explain the persistence of gas conduits in hydrate-bearing sediments and other nonequilibrium phenomena commonly observed in natural methane hydrate systems. © 2018 American Physical Society. Received 28 September 2017; revised manuscript received 16 January 2018; published 2 April 2018. We thank Carolyn Ruppel and William Waite from USGS for insightful discussions. This work was funded in part by the U.S. Department of Energy (Awards No. DE-FE0013999 and No. DE-SC0018357). L. C. F. acknowledges funding from the Spanish Ministry of Economy and Competitiveness (Grants No. RYC-2012-11704 and No. CTM2014-54312-P). L. C. F. and R. J. acknowledge funding from the MIT International Science and Technology Initiatives, through a Seed Fund grant. Published - PhysRevLett.120.144501.pdf