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CH4 hydrate dissociation, Mixed gas hydrates dissociation, Molecular dynamics simulation, Environmental changes, experiment > simulation > mathematical method, experiment > simulation > modelling
Abstract:
Gas hydrates are ice-like crystalline solids in which water molecules trap gas molecules in clathrate structures. They can preserve in low temperatures and elevated pressures and may exist in permafrost or deep marine environments. Natural gas hydrates are especially sensitive to the changes in temperature and pressure due to environmental changes. This can result in hydrate decomposition, which in turn may release enormous amounts of CH4 as the main component of natural gas hydrates. This study was an effort to use the molecular simulations for the estimation of possible gas release from the destabilization of natural gas hydrate reservoirs in response to environmental changes. The dissociation data for simple CH4 hydrates, CH4-C3H8 hydrates and CH4-C2H6-C3H8-CO2 mixed hydrates were provided by using molecular dynamics (MD) simulations. The MD simulations could provide a better understanding of the phenomena involved in the dissociation process of gas hydrates and help to explain the experimental observations. It would be one of the best molecular simulation tools for calculating time-dependent properties. The simple CH4 form structure I (sI) hydrates, while the above-mentioned binary and multicomponent gas mixtures can form structure II (sII) hydrates. Different simulation boxes were designed based on the structures and guest molecules of the gas hydrates. The simulation for CH4 hydrates was done via thermal stimulation above the ice point and depressurization below the ice point. For the mixed hydrates, the simulation data were only provided via thermal stimulation above the ice point. The dataset showed the simulation source files as well as the calculated time-dependent properties of gas hydrates upon the dissociation process. This included the simulation trajectories, gas density profiles, order parameters, ratios of large-to-small cavities, normalized rates of cavity decomposition, and gas compositions. This dataset contains the inputs/outputs of four simulation runs which include the molecular coordinate and structure (.gro file) and trajectory (.xtc file), as well as the calculated time-dependent properties (.vmd and .xls files) for each run. The simulation time and length were presented in nanoseconds (ns) and nanometers (nm), respectively. Further details on the simulation methodology, procedures, and calculations have been provided in the following sections.
