Comparative Evaluation of Thermal Stimulation Techniques for Natural Gas Hydrate Production

The issue of thermal loss during the depressurization extraction of natural gas hydrates has long been a significant challenge for achieving long-term stable production. In the context of thermal stimulation extraction, researchers have proposed four injection methods: hot water injection, steam injection, wellbore electric heating, and low-frequency electric heating, and have conducted relevant studies. However, a comprehensive evaluation comparing the advantages and disadvantages of these four thermal stimulation extraction methods is still lacking. This research, using a self-developed hydrate numerical simulator, constructed extraction class III hydrate deposits models for the four injection methods and conducted long-term extraction simulations over a period of five years. The results indicate that low-frequency electric heating significantly enhances extraction efficiency under various permeability reservoir conditions. Its ability to achieve a large heating range and provide wellbore protection confers distinct advantages. In contrast, the hot water injection method imposes stringent requirements on reservoir permeability. Both steam injection and wellbore electric heating exhibit notable similarities in multiple physical fields and fluid production outcomes. This study offers valuable insights and reference points for the selection of thermal stimulation methods in future hydrate extraction engineering.