Geological evaluation model for site selection of underground coal gasification without well in Jinghai coal-bearing area, Tianjin, China

Based on the 4 factors such as exploration status, coal seam, coal quality and hydrological conditions, using the secondary fuzzy comprehensive evaluation method, the geological evaluation model without well was built. In order to verify the applicability of the model, the material balance by law of conservation of mass was carried out and the results compared with the test results of indoor model was got. This research suggests that the weight of geological conditions affecting underground coal gasification without well is exploration status > conditions of coal seam > hydrological conditions > coal quality, the area with comprehensive score higher than 70 is the more suitable area, the area with score 60~70 is the suitable area and the area with score less than 60 is the unsuitable area. In the Jinghai coal-bearing area, the comprehensive score of the No.5 coal seam is 78.89 which belongs to more suitable area of underground coal gasification without well, and the buried depth, CO₂ reactivity(900℃), the poor cohesiveness and suitability made the score deducted. The gas components obtained from material balance and laboratory simulation tests have the relative error within 15% of the allowable error, and the relative error of useful components(H₂ +CO +CH₄) is 2.63%, which not only proves the applicability of the system, but also has certain guiding significance for the later production scale design and field production.