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

Abstract

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 construction. 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 conclusions 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.