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

在过去的十年里，人们对从水合物堆积中生产甲烷气体的兴趣急剧增加，这种巨大的非常规天然气供应提供了一种很有前途的未来能源资源。水合物还对常规海上油气储量的勘探和生产造成地质灾害；水合物解离与海底斜坡不稳定、天然气井喷和近井故障有关。水合物沉积对环境的影响可能是负面的，因为甲烷可能释放到大气中，也可能是正面的，因为二氧化碳可能以水合物的形式储存。天然气水合物是一种固体晶体化合物，由氢键水分子组成，形成由包裹的气体分子(主要是甲烷)稳定的刚性晶格。虽然我们对含水合物沉积物的地质力学性质的认识还不成熟，但实验和理论模型表明，水合物的存在会增加强度和刚度，降低渗透率；然而，水合物的解离会导致流体和天然气的产生，强度和刚度的损失，以及孔压的增加。

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.