Evaluation and Favorable Area Prediction of Deep CBM in the Southern North China Basin Using GRA-AHP

Abstract

To precisely delineate favorable coalbed methane (CBM) development target areas in the Southern North China Basin and to enhance the targeted efficiency of CBM exploration and exploitation, 10 structural blocks within the basin were selected as the study objects. Guided by the geological-engineering “dual sweet spots” evaluation framework, six core indicators were screened: coal seam thickness, burial depth, gas content, coal body structure, roof lithology, and permeability. Specifically, gas content, coal seam thickness, burial depth, and roof lithology were categorized as “geological sweet spot” parameters, whereas permeability and coal body structure were identified as key “engineering sweet spot” parameters. To overcome the limitations of single evaluation methods, Gray Relational Analysis (GRA) and the Analytic Hierarchy Process (AHP) were integrated to construct a subjective-objective collaborative comprehensive evaluation model. The final comprehensive weights were determined by combining the subjective and objective weights, which were then used to quantify the development potential scores of each block. Based on the score gradients, these areas were classified into Class I, II, and III favorable development zones. The results indicate that gas content, permeability, and coal seam thickness are the key factors governing CBM development potential in this basin. Ultimately, three Class I, five Class II, and two Class III favorable areas were identified. By balancing geological adaptability with engineering operability, this evaluation system and its classification results provide reliable theoretical support and technical references for the precise exploration deployment and efficient development planning of CBM in the Southern North China Basin.