Abstract：To study the mechanism of comprehensive evaluation of geological conditions for underground coal gasification ( UCG) , construct a quantitative feasibility evaluation system, and provide a basis for UCG site selection decision, taking geological structure, coal seam spatial distribution characteristics, hydrogeological conditions, and property of coal quality, the paper set up the fuzzy comprehensive evaluation system for UCG with hierarchy analysis, quantitative sorting, and fuzzing mathematics method. The favorable geological conditions for UCG were determined as follows: simple geological structure and hydrogeological conditions, respectively the thickness, depth and inclination of gasified coal seam were 1. 5 ~ 18 m, 100 ~ 1 500 m and 10° ~ 70°, respectively; the top and bottom lithology is mudstone and siltstone. The lower limits of coal qualities were as follows:A_d< 30%, M_ad< 20%; S_{t, d}< 1. 5%, V_daf> 20%; all types of coal except coking coal are acceptable. The above evaluation system was applied to the evaluation of UCG geological conditions in Zhuzhai minefield, and the favorable area suitable for UCG was selected. This has important practical significance for guiding the evaluation of UCG geological conditions in similar minefields in China.

Keyword：underground coal gasification;geological condition;evaluation system;Zhuzhai minefield;