Abstract: Considering it is difficult to determine index weight in evaluation model of spontaneous combustion risk of gas extraction drilling, an improved G2 weighting method based on CRITIC was proposed. Firstly, Euclidean distance function was introduced to establish an optimal decision-making model and CRITIC's "differential-driven" type weighting method was used to modify "function-driven" G2 weighting method. Secondly, comprehensive weight of each index was obtained, and primary and secondary relationship of risk factors that influence drilling spontaneous combustion was evaluated. Then G2-TOPSIS extraction drilling self-ignition risk assessment model was constructed based on TOPSIS "driving function" G2 weighting method, degree of closeness was analyzed, and risk level was predicted. Finally, this model was applied to gas extraction drilling of 1303 working face in Jinniu Coal Mine. The results show that temperature difference of coal oxidation-reduction ignition point was the dominant factor for extraction drilling spontaneous combustion which is rated as Class III, and prediction results of this model are consistent with actual situation.

Key words: gas extraction, prediction of drilling spontaneous combustion, comprehensive weight, criteria importance through intercriteria correlation (CRITIC) method, G2-technique for order preference by similarity to ideal solution (TOPSIS) evaluation model