Review and Outlook on Fracturing Technology and Mechanism of Hydrate-Bearing Sediments

Natural gas hydrates (NGHs) are widely distributed in marine and permafrost regions with huge reserves, which are considered one of the important potential sources for future clean energy. At present, China, Japan, the United States, Canada, etc. have conducted several trials; however, they all face varying degrees of challenges, such as low gas production efficiency and discontinuous production periods. In the oil and gas industry, hydraulic fracturing is a mature and highly efficient method for enhancing production through pressurization. Therefore, the successful application of fracturing technology to the NGH reservior is an urgently needed solution and could be a potentially revolutionary technology. This study summarizes the main recent fracturing advances in the hydrate field; it outlines the existing fracturing equipment for the NGH reservoir that differs from traditional oil and gas reservoir development, discussing the more efficient numerical simulation methods from the unit cell, experimental scale, to field scale. Additionally, it investigates the main controlling factors of fracturing behavior, such as the effects of fracturing fluid (viscosity and injection rate) and sample conditions (saturation, stress anisotropy, matrix, and natural fractures). The relationships and mechanisms proposed herein can provide new insights for understanding the fracturing behavior during hydrate exploration and constructing safe fracturing and extraction technologies.