Finite element simulation for fluid–solid coupling effect on depressurization-induced gas production from gas hydrate reservoirs

Abstract

Natural gas production from hydrate reservoirs is a physical and chemical seepage process of multiphase and multicomponent in nonisothermal condition. A gas–water two-phase hydro-mechanically coupled model is established to simulate the complex performance of depressurization-induced gas production from hydrate reservoirs. The model considers the heat conduction and convection, the variation of physical and mechanical properties as a result of hydrate dissociation, and the interaction between fluid seepage in porous and rock skeleton deformation. With the finite element approximation technique, a coupled simulator is developed. Case studies of gas production from hydrate reservoirs by depressurization are presented, and the fluid–solid coupling effect is mainly discussed.The results show that the overall fluid–solid coupling effect reduces the depressurization-induced gas production from hydrate reservoirs. The rock skeleton deformation can shrink reservoir porosity and increase the elastic drive energy, which favors to enhance gas production to some extent. In contrast, the permeability and porosity reduction due to sandstone deformation can lead to the decrease of gas production significantly. The physical properties variation in the fluid–solid coupling effect has a major impact on gas production of hydrate reservoirs. The fluid–solid coupling effect is a key factor worthy of close attention in the exploitation of hydrate reservoirs.