Mechanical stability of the CO 2 −CH 4 heteroclathrate hydrate dominates the geomechanical stability of natural gas hydrate deposits when CO 2 replaces CH 4 from gas hydrate reservoirs. Here, molecular dynamics simulations were employed to investigate the strain-induced fracture behaviors of the CO 2 − CH 4 heteroclathrate hydrate under mechanical loadings at various temperatures, pressures, and CO 2 saturations. Results show that all crystals exhibit brittle fracture behavior, and a crack first develops in the location where hydrogen bonds (HBs) in the hexagonal rings of the large 5 12 6 2 cages are parallel to the tensile direction. Increasing the temperature or CO 2 saturation leads to the decrease in Young's modulus and fracture strength of the CO 2 −CH 4 heteroclathrate hydrate. Particularly, abnormal mechanical strengthening of hydrates is observed when the CO 2 saturation is around 0.75, mainly attributed to the coupling of the lattice distortion with the host−guest interaction. HBs are the key factors to dominate the deformation of the CO 2 −CH 4 heteroclathrate hydrate. The slow decrease, rapid decrease, and abrupt increase in HB dynamics are corresponding to the elastic deformation, elastic−plastic deformation, and brittle fracture of the CO 2 −CH 4 heteroclathrate hydrate, respectively. With the further stretching after the brittle fracture, the water bridge made up of water molecules released by broken cages at high temperatures leads to different plasticity than at low temperatures and causes a further reduction of HBs. This work advances the understanding of mechanical stability of the gas hydrate, which is believed to be useful in the risk assessment of CO 2 replacing CH 4 from natural gas hydrates and the storage of CO 2 in gas hydrate reservoirs.

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To mitigate high pressure under-injection with the purpose of depressurization and augmented injection in low-permeability reservoirs, an efficient strategy is proposed based on the electric resonance of the hydrogen bond that is induced by an oscillating electric field. We studied the effects of the electric field on water microscopic structures, dynamics properties, flow, and injection in the nanopore composed of two hydrophilic quartz layers using molecular dynamics simulations and density functional theory calculations. The electric resonance generated by the electric field with a frequency of 16,910 GHz induces the breakage of the hydrogen-bonded network to the largest extent, thus greatly improving the movability of water in the nanopore mainly depending on the following mechanisms: (1) the water tetrahedral structure is destroyed, and water molecules in the first coordinate shell decrease; (2) water diffusion is enhanced, the adsorption residence time of water becomes shorter, and the hydrogen bond retaining intact lasts much shorter; and (3) water flow velocity at the nanopore center and surfaces is greatly increased, the slippage length becomes larger, and the apparent viscosity of water is reduced. Consequently, the electric resonance can effectively reduce the pressure and increase the efficiency for water injection development in low-permeability reservoirs.