Numerical prediction of seabed subsidence with gas production from offshore methane hydrates by hot-water injection method

Seabed subsidence is studied by comparing experimental data with the results of a numerical model for gas production from an offshore methane hydrate (MH) reservoir using the hot-water injection method. To predict seafloor displacement, geo-mechanical reservoir models, such as the consolidation– permeability compound model, are required to simulate MH dissociation and consolidation by depressurization in the MH reservoir. In this study, we constructed a field-scale model of gas production from a MH reservoir induced by hot-water injection using dual horizontal wells. Compared with the depressurization method, this method required less depressurization to produce the same amount of gas with pressure drawdown up to 10MPa. This causes less seabed subsidence; therefore, the hot-water injection method is a more environmentally friendly gas-production method for offshore MH reservoirs.