Experimental investigation of the shear strength of gas hydrate-bearing sediments

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Interest in methane gas production from hydrate accumulations has increased dramatically in the last decade, with this vast supply of unconventional gas offering a promising future energy resource. Hydrates also pose a geohazard in exploration and production of conventional offshore hydrocarbon reserves; hydrate dissociation has been linked to submarine slope instability, gas blowouts, and near well failures. Environmental implications of hydrate deposits can be negative owing to potential methane release to the atmosphere, or positive as prospective storage of carbon dioxide in hydrate form. Gas hydrates are solid crystalline compounds comprised of hydrogen-bonded water molecules forming a rigid crystal lattice stabilized by encaged gas molecules, predominately methane. Although our knowledge of the geomechanical properties of hydrate bearing sediments is immature, experimental and theoretical models demonstrate that the presence of hydrate will increase strength and stiffness and decrease permeability; however, dissociation of hydrate induces fluid and gas production, loss of strength and stiffness, and elevated pore pressures.