Fracability evaluation method of hydraulic fracturing of coal seam based on fuzzy comprehensive evaluation

In order to expand an adaptive evaluation method for the fracability of coal seam hydraulic fracturing,six on-site case studies from mining working faces were used as samples and the main controlling factors affecting the fracability of coal seam hydraulic fracturing were determined in combination with experimental tests. Based on fuzzy comprehensive evaluation theory,a combination weight for each factor was determined using Analytic Hierarchy Process (AHP) and entropy weight methods. This led to the establishment of a model for evaluating coal seam fracability based on “ indicator input-effect output-actual fracturing effect verification” thinking. The evaluation results show that under a confidence level satisfying “ reasonably effective” criteria (α>0. 5),the fracability of coal seams in Gaocheng Coal Mine’s 25011 working face and 25031 working face shows medium to poor levels,while Songzao Coal Mine exhibits good to medium levels,and Sijiazhuang Coal Mine’ s 15301 working face and 15118 working face demonstrate good levels. The evaluation results are basically consistent with actual hydraulic fracturing effects observed on site,thus validating both the rationality of selecting indices for evaluating coal seam fracability and the feasibility of employing fuzzy comprehensive evaluation methods. The research results show that most significant factor influencing coal seam fracability is found to be firmness coefficient. However,it should be noted that wetting properties and clay mineral content also have considerable impact which cannot be overlooked. Conversely,depth had relatively minor influence within selected case samples.