A novel thermal stimulation approach for natural gas hydrate exploitation - the application of the self-entry energy compensation device in the Shenhu sea

Thermal stimulation is a common measure used to improve the decomposition efficiency of natural gas hydrate. However, the conventional thermal stimulation methods require considerable investments in wellbore con-struction. According to the penetration mechanism of the torpedo anchor, the self-entry energy compensation device (ECD) is innovatively proposed to replace the existing wellbore platform. The principle and critical technologies of the ECD are described and analyzed in detail. Then, a penetration model and an exploitation model are developed using the reservoir data from the W17 station in the Shenhu sea area, and the main con-clusions are: It takes about 4 s for the ECD to penetrate from the overburden layer to the reservoir, and its penetration depth is about 50.1-370.4 m, which covers the buried depth of most marine reservoirs. Nevertheless, the combined depressurization + thermal stimulation method is unsuitable for the Shenhu reservoir due to the low permeability, low thermal conductivity, and high initial temperature. Overall, the ECD can provide a new idea for developing the NGH thermal stimulation method to solve the Joule-Thomson effect and seawater freezing problems during the depressurization production.