降低井下煤层压裂起裂压力方法研究

A Novel Method for Decreasing Coal Seam Fracture Initiation Pressure

为减少煤矿井下水力压裂高水压对顶底板破坏形成的次生灾害,提出采用水射流在煤孔中定向射孔,以降低起裂压力,避免顶底板次生灾害。通过分析射孔煤体受力状态,基于线弹性理论建立钻孔射孔起裂压力计算模型。对比钻孔射孔及普通钻孔的起裂压力。结果表明,射孔能够改变钻孔应力分布,降低煤体的起裂压力,且起裂压力降低的幅度受水平主应力比值影响。采用RFPA2D-Flow对比分析钻孔射孔前后起裂压力,计算结果与理论结果相吻合。将该方法应用于鱼田堡煤矿-350 m东抽放巷,证明钻孔射孔能够降低起裂压力,减轻对顶底板的伤害。

A novel method for decreasing coal seam fracture initiation pressure was worked out, with which perforation, developed by high pressure water jet, was used as a mean for avoiding destroying roof and floor. On the basis of analysis of perforation stress, two models were built, for predicting initiation pressure of hydraulic fracture with perforation and without perforation respectively. An initiation pressure comparison was made between perforation and drill holes. The result showed that perforation did decrease the fracture initiation pressure due to change of stress distribution, and that the main stress ratio affects the decrease in initiation pressure. The results showed before were in accord with those of numerical simulation of RFPA2D-Flow. The application results obtained in 350 m drainage lane in Yutianbao mine in China veri- fied again those conclusions.