Gas hydrates are crystalline inclusion-compounds with gas molecules trapped in a host lattice formed by water molecules in an ice-like hydrogen-bonded framework. Gas hydrates naturally exist as a bulk phase in the permafrost region or as a dispersed phase in ocean-floor sediments at low temperatures and high pressures. Gas hydrates are an untapped energy resource, but also a potential contributor to global warming. It is then important to predict accurately the extents of zones of stability and formation of methane-hydrate within possible hydrate deposits. In this work, we will present new models developed in order to predict stability and nucleation of gas hydrates in porous media. The models, based on thermodynamic principles, incorporate sediment interfacial properties into the conditions of thermodynamic equilibrium and activation energies for gas-hydrate nucleation. <br/>Model predictions predictions show very good agreement with experimentally-measured equilibrium data for gas hydrates in synthetic sediments. Model predictions for hydrate nucleation were compared qualitatively with visual observations of gas-hydrate cores. Model predictions suggest that nucleation of methane hydrates preferentially occurs in large sediment pores rather than in small sediment pores. Modeling predictions show that gas hydrates form first on the gas/liquid interface, then on the gas/liquid/solid triple boundary lines and last on liquid/solid interfaces. The models presented in this work can be applied in the design of technologies for harvesting methane and natural gas from hydrate deposits, and, most importantly, predict destabilization of those deposits that may result in catastrophic gas release to the atmosphere.

Prediction of gas-hydrate stability and nucleation in porous media

ACS Spring 2022

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