Potential of Enhancing Methane Production from Four Typical Types of Natural Gas Hydrate Reservoirs by Different Stimulation Methods

Extensive natural gas hydrate deposits have been identified in the Krishna-Godavari Basin (KGB-India), the eastern Nankai Trough (ENT-Japan), the South China Sea (SCS-China), and the Alaska North Slope (ANS-US). Reservoir stimulation techniques present a viable approach to enhance their inherently low methane (CH4) production rates. Given the distinct geological characteristics of these reservoirs, tailored stimulation strategies are required. This study establishes conceptual reservoir models parameterized using field data from the four regions and numerically evaluates the performance of thermal injection (Ti), multistage hydraulic fracturing with horizontal wells (HF), boundary sealing (BS), and their combinations. The results demonstrate that permeable boundaries substantially weaken depressurization performance and diminish the benefits of HF and Ti. In the KGB-India reservoir, insufficient sensible heat makes depressurization alone ineffective, with the optimal strategy being a combination of Ti and BS. Conversely, the ENT-Japan reservoir possesses adequate sensible heat to sustain depressurization, and BS further enhances CH4 production rate by a factor of 12.5. The low permeability in the SCS-China reservoir necessitates HF, and when combined with BS, a 21.2-fold increase in CH4 production rate can be achieved. For the ANS-US reservoir, the synergistic application of BS, HF, and Ti is recommended and yields a 7.2-fold improvement in production rate.