Classification of natural gas hydrate resources: Review, application and prospect

Abstract

Natural gas hydrates (NGHs) have attracted considerable attention due to their abundant reserves, widespread distribution, and high energy density. Successful commercial extraction of NGHs could lead to a significant reduction in coal and oil consumption, ultimately mitigating the greenhouse effect and ameliorating global environmental problems. Despite over ten global hydrate pilot productions, there is currently no universally accepted classification system or international standard for naturally occurring NGH resources within the industry. This work highlights the importance of classifying NGH resources in order to initiate their exploitation. In this review, we summarize and evaluate various studies conducted on the classification of NGH resources and thoroughly analyze the potential applications of these classification systems. While non-quantitative observations and analyses predominate, the exploitation of specific technological breakthroughs will rely on quantitative reservoir descriptions. The applicable extraction methods for different types of NGH reservoirs and the challenges faced during the exploitation process were discussed. A thorough analysis of future directions in NGH classification research was presented, and this review suggests that the exploitation trend lies in the combination of NGH resource classification and various hydrate exploitation technologies. Priority should be given to the exploitation of NGH reservoirs with better reservoir conditions, higher yields, and lower risks.