Numerical Evaluation of Gas Hydrate Production Performance of the Depressurization and Backfilling with an In Situ Supplemental Heat Method

The depressurization and backfilling with an in situ supplemental heat method had been proposed to enhance the gas production of methane hydrate reservoir. This novel method is evaluated by a numerical simulator based on the finite volume method in this work. Based on the typical marine low-permeability hydrate-bearing sediments (HBS), a reservoir model with gas fracturing and CaO powder injection is constructed. The simulation results show that the stimulated fractures could effectively enhance the pressure drop effect. Moreover, the CaO injection could provide in situ heat simultaneously. Based on the sensitivity analysis of the equivalent permeability of fractures and the mass of CaO injection, it is found that a threshold fracture permeability exists for the increasing of gas production. The gas production increases with the equivalent permeability only when the permeability is smaller than the threshold value. Meanwhile, the more CaO are injected into reservoir, the larger volume of gas production. In general, this work theoretically quantifies the potential value of the depressurization and backfilling with an in situ supplemental heat method for marine gas hydrate recovery.

Automated summary

A novel method of depressurization and backfilling with in situ supplemental heat has been proposed to enhance gas production in methane hydrate reservoirs. Numerical simulations show that stimulated fractures and CaO injection can effectively enhance pressure drop effects and provide in situ heat. Sensitivity analysis reveals the existence of a threshold fracture permeability for increasing gas production, with gas production increasing with smaller permeabilities and larger CaO injections. Overall, this work theoretically quantifies the potential value of this method for marine gas hydrate recovery.