The geomechanical behaviour of natural and synthetic gas hydrate bearing sediments

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Production of methane gas from naturally occurring hydrate accumulations offers a vast supply of environmentally sustainable unconventional gas, a promising future energy resource. Gas hydrates are crystalline compounds comprised of hydrogen-bonded water molecules forming a rigid lattice stabilized by encaged methane molecules. These “ice-like” solids form at high pressures and low temperatures; hence they are found within the pore space of sediments located below the permafrost in the Arctic or beneath the seafloor on the continental slopes and margins. The technology used during gas hydrate drilling and characterization expeditions has recently undergone colossal change, the result of which has been a quantum leap in our understanding of natural gas hydrate systems. Because gas hydrate dissociates rapidly when recovered with conventional coring, pressure-coring techniques were developed to “lock in” the in-situ hydrostatic pressures and pressure chamber transfer and analyses systems built to subsequently characterize the undisturbed sediment core. Utilizing these systems, comprehensive datasets, gathered as recently as this summer, may offer game-changing insights into natural gas hydrate bearing systems. This research program examines the link between this newly available information on natural hydrate bearing sediments and their synthetically constructed laboratory analogs, furthering our understanding of both systems, and ultimately our ability to model reservoir geomechanics in natural hydrate accumulations during methane gas production. The research approach involves a combination of laboratory testing, numerical modeling, and critical comparison/analysis with the most up-to-date data from natural gas hydrate core. A new baseline of our knowledge of natural hydrate properties will be established through careful scrutiny of the datasets amassed during recent arctic and marine gas hydrate expeditions. Creativity, innovation, and collaboration will be the instigation for developing highly novel laboratory processes to produce synthetic hydrate-bearing specimens that mimic natural samples. Focused experimental programs aim to define fundamental properties and examine the meso-level response, and to ultimately provide the input, calibration, and verification data for constitutive models. Up scaling to reservoir-level simulations enables probing, understanding, and prediction of the sediment response (reservoir stability, subsidence, and associated geohazards) during gas production from hydrate accumulations. Gas hydrates are an important component of Canada’s unconventional energy supply; research and development of this frontier gas aligns with our priorities to increase northern development, exercise arctic sovereign rights, and optimize energy recovery while reducing economic and environmental impacts.