Development of a novel suction cylinder exploitation device for marine natural gas hydrate and the feasibility studies

Abstract

Natural gas hydrate (NGH), a novel clean energy with enormous potential, has drawn the attention of many countries for research and development. In recent years, exploitation theories and technical capabilities have advanced quickly. However, commercial production, in terms of current exploitation equipment and tried tests, is still challenging to implement. In this paper, a novel suction cylinder exploitation device (SCED) was proposed based on marine NGH depressurization exploitation technology and suction anchor to replace conventional wellbore. The SCED is a prefabricated steel construction that enters the NGH reservoir by suction and gravity and has the potential to be recycled after exploitation. Through indoor experiments, the SCED penetration mechanisms and characteristics were investigated to confirm whether it can smoothly penetrate the NGH reservoir. Simultaneously, the gas production situation of the SCED was explored by CMG software. Results show that: (i) the super sizeable length-to-diameter ratio SCED model can complete the penetration from the experimental results. Although the “soil plug” height increases with the increase of the length-diameter ratio, it can be solved by taking appropriate methods for specific engineering; (ii) Due to the larger diameter and higher strength of the SCED, it can achieve greater pressure reduction and exploitation range, making the efficiency of gas production roughly 5.7–11.77 times greater than that of a conventional wellbore. In summary, it is anticipated that the SCED will open up new opportunities for the early commercial exploitation of marine NGH due to its advanced advantages of high equipment strength, big exploitation diameter, and easy construction.