Coupled Numerical Modeling of Gas Hydrate‐Bearing Sediments: From Laboratory to Field‐Scale Analyses

Methane hydrates are ice‐like compounds made of gas methane and water. Hydrates are stable under low‐temperature and high‐pressure conditions constraining their occurrence in sediments to marine and permafrost settings. A shift from the stability condition triggers an endothermic hydrate dissociation with the associated release of gas and water, impacting (among others) on sediment pore pressure, temperature, and deformations. Therefore, the behavior of hydrate‐bearing sediments (HBS) is controlled by strongly coupled thermo‐hydro‐chemo‐mechanical actions. The analysis of available data from past field and laboratory experiments and the optimization of future field production studies require a formal and robust numerical framework able to capture the complex behavior of this type of soil. In this paper we used a fully coupled thermo‐hydro‐mechanical framework to study different problems involving HBS, from laboratory experiments involving natural hydrate samples to gas production tests. We also develop an analytical solution for the case of gas production via radial depressurization from a confined HBS reservoir. The analyses show the complexity of the thermo‐hydro‐mechanical phenomena associated with this type of system and contribute to better understand the behavior of HBS. Key Points A fully coupled consistent/dependable approach to tackle problems involving HBS with a novel kinetic law to model phase transformations An analytical solution related to gas production via radial depressurization from a confined HBS reservoir at steady state conditions Modeling of a lab test simulating gas production from a heterogeneous HBS specimen involving hydrate dissociation and ice formation/thawing