关键词: 天然气水合物, 拉削开采, 采空区, 安全评价, 日产气量

Abstract: At present, the main methods for extracting natural gas hydrates are thermal extraction, vacuum extraction and chemical reagent extraction. They are mainly used for the development of diagenetic hydrate reservoirs in tight cap rocks, and cannot be used to extract shallow non-diagenetic hydrates that account for 85% of deep water resources. Taking the Shenhu area of the South China Sea as the mining target area, a new type of broaching exploitation method was proposed on the basis of solid-state fluidization theory. A three-dimensional model of broaching exploitation method was established, the working principle, working steps and stope distribution of the new technology were explained in detail, and a broaching tube was designed for broaching, collecting and transportation mining tools. Use the knowledge of geotechnical mechanics to analyze the shear stress of the goaf produced by the broaching exploitation method can ensure that the goaf does not collapse and obtain the maximum stope volume. The force analysis of the broached pipe according to the mining conditions ensured that the broached pipe can work safely and stably. Finally, the daily gas production of the broaching technology was estimated. The results showed that the larger the goaf radius and the mining angle were, the more obvious the shear stress concentration in the goaf. The maximum shear stress occurred at the start and end positions of the upper part of the goaf. The maximum stress of the broaching tube during the mining process was less than the yield stress of the material. The daily gas output of the broaching technology was estimated to be 142000 m3, which had practical application potential.

Key words: natural gas hydrate, broaching, goaf, safety evaluation, daily gas production