FEM-based simulation of decomposition process of gas hydrate-bearing sediments

The variation of temperature and pressure may lead to decomposition of gas hydrate in a hydrate-bearing sediment (HBS); meanwhile, several coupling processes are induced, including phase transition, pore water and gas pressures dissipation, heat transfer and skeletal deformation. A mathematical model is developed to describe the decomposition process of gas hydrate-bearing sediments based on the theory of porous media. The model properly considers the coupling effect among pore water/gas flow, phase transition, the kinetic process of hydrate dissociation, heat transfer and the skeletal deformation. Based on the finite element method, a numerical model describing the process of gas hydrate decomposition is developed and a computer program is compiled. Through numerical simulation of both depressurization-based and heating-based production processes, variation of displacement, pore pressures, temperature and other parameters in gas hydrate bearing sediments reservoir are analyzed. The results indicate that reservoir deformation and excess pore pressure are induced by depressurization and heating method with varying degrees, meanwhile, the seepage and heat conduction are contained in the gas hydrate dissociation process.