Pore-Scale Investigation Of Methane Hydrate-Bearing Sediments Under Triaxial Condition

Mechanical behavior of hydrate-bearing sediments is critical for well stability, reservoir deformation, and sea floor settlement during gas production. Current understanding on the mechanism of hydrate strengthening hosting sediments relies on conceptual models based on idealistic pore-scale assumptions. Yet pore-scale study is rare and limited to hydrate-bearing sediments formed with surrogate guest molecules rather than methane. We present for the first time pore-scale triaxial test results of methane hydrate-bearing sediments. Besides the traditional stress-strain relationship, we further explored (1) sand particle crushing and (2) pressure-temperature dependent strength variations and (3) creep of hydrate-bearing sediments. Results show that as hydrate enables the sand skeleton to bear additional loads, the potential of sand crushing upon hydrate dissociation also increases. Strength of hydrate-bearing sediments decreases as pressure-temperature condition approaches hydrate phase boundary. Hydrate-bearing sediments creep and heal with time. The new observations suggest additional complications to be considered during gas production.