A comprehensive review in natural gas hydrate recovery methods

Natural gas hydrate is an ice-like compound composed of mainly methane molecules and water molecules under proper high pressure and low temperature, and is being studied as a strategic energy resource. This paper first introduces the research advance of reservoir formation and classification of hydrate formation, and then systematically summarizes the current methods and their applicable conditions for hydrate exploitation. A new concept i.e. mechanical-thermal hydrate recovery method is presented based on the geological-mechanical characteristics in China and the technological process and scientific principles were introduced and overiewed. Hydrate mining mainly involves four effects of heat conduction, phase change, seepage and stress change. Through the analysis of the four characteristic time, the problem is decoupled and the characteristics of the evolution of the physical quantities in the process of hydrate mining can be determined, which can provide theoretical guidance for the practical exploitation of hydrates. Finally, the research progress of field trial production is analyzed and the future research direction of hydrate mining is pointed out.