Prof. D. N. Singh

LIJITH K. P.

Ph. D.
Indian Institute of Technology Bombay, Powai, India nambiar.lijith@gmail.com

Methane gas hydrates (MGH) which are hosted in gas hydrate bearing sediments (GHBS), located beneath the ocean bed and permafrost regions, are considered as a panacea to meet the huge energy requirements of the present-day society. GHBS are a multi-phase system that comprise of ice crystals and gas hydrates apart from the soil minerals, water and gas (read as methane). 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), multi-phase, multi-component heat flow and mass flow and their mechanical stability. Hence, the establishment of the thermo-hydro-mechanical properties of GHBS is of paramount importance for the safe and efficient production of methane gas from GHBS. With this in view, an extensive review of the literature was conducted on the permeability and geomechanical properties (viz., shear strength, stiffness, dilation, and stress-strain characteristics) of GHBS and the factors (viz., hydrate saturation, hydrate morphology, confining pressure and temperature) influencing them. Through this exercise, the generalized relationships have been proposed that can be employed for estimating the geomechanical properties of GHBS. Incidentally, as synthesis 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 for establishing the soil freezing characteristics curve, thermal (by TheFros) and shear strength characteristics (by DSBTemp), and synthesizing gas hydrates (by GHSS). A critical synthesis of these results reveals that temperature, volumetric ice content and unfrozen water content influences the thermal and shear strength properties and volumetric ice content of the fine-grained sands. Efforts have also been made to investigate the influence of various parameters (viz., production condition, permeability anisotropy and wellbore configuration) on the optimal methane gas and water production from a typical turbidite reservoir of Krishna Godavari Basin, India, by employing depressurization in tandem with the wellbore heating.