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Unveiling the Realm of Thermo-Hydro-Mechanical Characteristics of Gas Hydrate Bearing Sediments
Lijith K P and D.N. Singh

Methane gas hydrates (MGH), which are hosted in gas hydrate-bearing sediments (GHBS) located beneath the ocean bed and permafrost regions, are considered a panacea to meet the huge energy requirements of present-day society. GHBS are a multiphase system that comprises gas hydrates and ice crystals (in permafrost regions) apart from the soil minerals, water and gas. It is worth realising that the production of methane gas from GHBS is a complex process that couples phase transition (MGH to water and methane gas), multiphase, multi-component heat flow and mass flow and their mechanical stability. Hence, establishing the thermo-hydro-mechanical properties of GHBS is paramount for the safe and efficient production of methane gas from GHBS. As the formation of hydrates deals with exposure of the sediments to low temperatures and high pressures, needs-based laboratory setups and instrumentation were developed, and their utility has been demonstrated in this paper for establishing the soil freezing characteristics curve, thermal and shear strength characteristics, and synthesising gas hydrates. A critical synthesis of these results reveals that temperature and volumetric ice content influence the thermal and shear strength properties and volumetric ice content of the fine-grained sands. At the same time, the compression and shear wave velocities of gas hydrate-bearing fine-sands were found to depend on the hydrate saturation. Efforts have also been made to model the methane gas production from a typical turbidite reservoir of Krishna Godavari Basin, India, by employing vertical and horizontal wellbores.

Keywords: gas hydrate-bearing sediments, synthesis, soil freezing characteristic curve, thermal properties, heat migration characteristics, shear strength, depressurisation