煤层巨厚砂岩顶板定向长钻孔水力压裂矿震防治技术研究

Study on mine earthquake prevention technology of directional long drilling hydraulic fracturing in super thick sandstone roof of coal seam

针对东滩矿工作面采掘期间易造成煤层巨厚砂岩顶板应力失稳等问题,以63_(上)03工作面巷道及上覆岩层为施工区域,通过岩性分析、关键层判断及现场实际综合比较,确定关键层位施工顶板定向长钻孔,并进行水力压裂,为东滩矿煤层巨厚砂岩顶板定向长钻孔分段水力压裂矿震防治提供技术支撑。结果表明:选定二叠系山西组上段中砂岩层、侏罗系三台组下段细砂岩层为钻孔施工关键层位;完成4个顶板定向长钻孔钻探施工,形成顶板连续滑动钻进工艺,单孔孔深为519~800 m,总进尺2517 m;通过4个钻孔的分段压裂工程施工形成了东滩矿煤层顶板双封单卡后退式分段压裂工艺,分段压裂施工累计25段,总注水量为1286 m^(3),施工压力为17.1~32.8 MPa,压力曲线明显反映了破裂点,最大压力降低幅度超过10 MPa;水力压裂施工大幅度降低了震级大于2级和1~2级微震事件的发生频次,同时压裂后的工作面支架循环末阻力平均值降低了1.2 MPa,周期来压步距降低了7.3 m,治理矿震的效果较为有效。

In view of the occurrence of rock shock and other disasters during the working face excavation in Dongtan mine,the stress instability of the roof of the coal seam is easy to occur,with 63_(上)03 working face roadways and overburden as construction area,through the key stratum lithology analysis,judgment and actual comprehensive comparison,determine the key construction of roof strata directional drilling,and hydraulic fracturing,long for the thick sandstone roof in comprehensive coal directional drilling section hydraulic fracturing rock burst prevention and control to provide technical support.The results show that the middle sand strata in the upper part of the Permian Shanxi formation and the fine sand strata in the lower part of the Jurassic Santai formation are selected as the key strata for drilling.The construction of 4 roof directional long drilling has been completed,forming the roof continuous sliding drilling technology,with a single hole depth of 519-800 m and a total length of 2517 m.The segmental fracturing technology of double sealing and single block backward fracturing of coal seam roof of Dongtan mine is formed through the segmental fracturing of four boreholes.There are 25 sections of segmental fracturing,with a total water injection volume of 1286 m^(3) and a construction pressure of 17.1-32.8 MPa.The pressure curve clearly reflected the fracture point,and the maximum pressure drop exceeded 10 MPa.At the same time,hydraulic fracturing greatly reduces the occurrence frequency of seismic events greater than magnitude 2 and magnitude 1-2 microseismic events.Meanwhile,the average value of the final resistance of the working face bracket after fracturing is reduced by 1.2 MPa,and the periodic pressure step distance is reduced by 7.3 m,which has achieved the effect of mine earthquake control.