Evaluation of the depressurization based technique for methane hydrates reservoir dissociation in a marine setting, in the Krishna Godavari Basin, east coast of India

•Effectiveness of depressurization technique evaluated for the KG basin hydrate reservoir.•Using Tough + Hydrate software identified a ΔP of 80 bar for sustained dissociation.•Well reach analyzed using MATLAB for various Post Dissociation Permeability (PDP).•Vertical well in the reservoir with a 500 mD PDP could dissociate up to 1000 m.•Pump with a motor capacity of 296 kW is required to dissociate up to 1000 m.

This paper analyses the effectiveness of the depressurization technique for methane gas production from an unconfined gas hydrate setting in the Krishna Godavari Basin of India. TOUGH + HYDRATE reservoir modeling and production simulation software is used for identifying the depressurization range for sustained dissociation. For the identified depressurization range, a borehole based pumping technique is modeled using MATLAB software, to identify the effectiveness of the technique in dissociating the reservoir with post-dissociation permeability (PDP) ranging between 1 and 500 mD, the likely scenario for the KG basin. The results indicate that the depressurization technique shall be effective for reservoirs with higher PDP, while the reach of the bore well depends on the capacity of the pump and hydrate zone well perforation area. The simulation results indicate that a bore well with 50 m2 of hydrate zone surface area could be effective in dissociating the reservoir up to a distance of 1000 m, with a pump of 128 kW electric capacities in formations with PDP of 500 mD. The results could serve as a basis for the economic planning of production wells in gas hydrate reservoirs.