DEVELOPMENT HISTORY AND KEY MECHANICAL PROBLEMS OF WELL DRILLING UNDERGROUND COAL GASFICATION TECHNOLOGY¹⁾

Underground coal gasification technology is important in the context of China's energy crisis, for the efficient and clean utilization of coal resources, and for expanding the natural gas resources to realize the strategic resource replacement. Based on the investigation of underground coal gasification technology at home and abroad, this paper divides underground coal gasification technology into two categories, namely drilling technology and roadway technology, and focuses on the development mode of drilling underground coal gasification technology. The technology development of the well drilling UCG can be divided into four stages: (1) the basic theory research stage; (2) the borehole method technology development mode stage; (3) the linked vertical well development mode stage with different channel breakthrough methods; (4) the horizontal well development mode stage. This paper focuses on the key technology of three development modes in the UCG process, including the borehole mode, the vertical well drilling mode and the horizontal well drilling mode. By comparing different uses of these technology modes, the advantages and disadvantages are evaluated in detail. On the basis of summarizing the development process of underground coal gasification technology development mode, this paper points out the development trend of underground coal gasification technology, which has a positive guiding significance for the coming commercial development of underground coal gasification in China.