A Novel Wellbore-Wall Heating Method without External Energy Injection for Natural Gas Hydrate Production—A Heat Transfer Device

Natural gas hydrate (NGH) dissociation is a heat-absorbing process, and the cooling around the wellhead is more pronounced during depressurization production. Low temperature will cause NGH regeneration or ice formation, blocking gas flow paths and reducing extraction efficiency. In this study, a novel heat transfer device (HTD) was innovatively proposed to alleviate this problem. Theoretical analysis and numerical simulations were used to research the methodological principles, applicable conditions, and expected benefits of the HTD. Results show that the HTD utilizes the characteristics of the geothermal gradient to rapidly transfer energy from the lower reservoir to the wellbore wall, which in turn raises the temperature and prevents the ice and NGH regeneration causing the blockage from adhering to the wellbore wall. The heat transfer radius, the length of the endothermic section, and the operating temperature difference make a tremendous difference in the heat transfer efficiency of the HTD. The HTD may be more suitable for Class 1 reservoir conditions and help to improve gas production under the depressurization method in the Shenhu sea of the South China Sea. The device can achieve continuous self-heat transfer without external energy injection to significantly reduce costs, which provides a new idea for marine NGH production.