A review of the resource potentials and test productions of natural gas hydrates in China

China has been attaching great importance to research on natural gas hydrate resources. Since the mid-1990s, China has experienced three development stages of resource prediction, investigation, and test production of natural gas hydrate resources. Till now, five hydrate samples have been discovered in Shenhu, Dongsha, Qiongdongnan, offshore Taiwan of the South China Sea and in the Muli area of Qilian Mountain, with seven hydrate occurrences inferred including geology, geophysics and geochemistry in the South China Sea, the Okinawa Trough of the East China Sea, and the Tibetan Plateau. According to the hydrate stability zone, the natural gas hydrate resources in the South China Sea are estimated to be 64×10¹² m³, those in the Okinawa Trough are about 24×10¹² m³, and those in the terrestrial permafrost are about 38×10¹² m³. The total amount of the natural gas hydrates in China reaches up to 126×10¹² m³, which is twice the amount of China’s conventional natural gas resources. Since 2011, China has carried out five test productions of hydrates in the Muli area of Qilian Mountain and in Shenhu area of the South China Sea using depressurization and heating methods, with gas production of 117×10⁴m³. It is probable to exploit hydrates in large-scale fine-grained reservoirs located at the base of the classification ‘pyramid’.