基于模糊综合理论的煤层水力压裂可压性评价方法
Fracability evaluation method of hydraulic fracturing of coal seam based on fuzzy comprehensive evaluation
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摘要: 为拓展适应性的煤层水力压裂可压性评价方法,以6个采煤工作面现场案例为样本,结合实验测试确定影响煤层水力压裂可压性的主控因素。基于模糊综合评价理论,运用层次分析法(AHP)和熵权法确定各因素的组合权重,建立以“指标输入—效果输出—实际压裂效果验证”为思路的煤层可压性评价模型。评价结果显示:在满足“比较有效”置信度下(α>0.5),告成煤矿25011和25031工作面煤层可压性中等偏差,松藻矿区煤层可压性良好偏中等,寺家庄矿15301和15118工作面煤层可压性均为良好。评价结果与现场水力压裂效果基本一致,验证了所选择的煤层可压性评价指标的合理性及模糊综合评价方法的可行性。研究结果表明,影响煤层可压性最重要的因素是煤的坚固性系数,润湿性与黏土矿物含量的影响不可忽略,而案例样本中埋深的影响相对不大。Abstract: 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.