赵固二矿本煤层定向长钻孔水力压裂增透技术研究

Study on Permeability Enhancement Technology through Overall Hydraulic Fracturing of Long Directional Hole in Zhaogu No.2 Coal Mine Mining Coal Seam

为了提高井下低透气性煤层瓦斯抽采钻孔瓦斯抽采效果,开发了适合中等偏硬低透煤层裸眼钻孔高压稳定封孔装备,采用了本煤层定向长钻孔整体水力压裂增透技术,分析了本煤层定向长钻孔水力压裂增透机理,并进行了水力压裂强化增透试验。根据压裂施工过程中压裂参数变化规律,利用压裂前后煤层全水分和钻孔瓦斯参数变化对比,综合考察和评价了水力压裂增透效果和影响范围。研究表明:压裂过程中最大注水压力24. 6MPa,发生多次明显压降,最大压降5. 2MPa。水力压裂增透后,煤层瓦斯日抽采纯量提高了12. 70倍,百米钻孔瓦斯抽采量提高了2. 67倍,压裂最大影响半径达到了38m,平均超过30m,提高了瓦斯抽采效率。

In order to improve the underground gas drainage effect of coal seam with low permeability,the hydraulic fracturing technology of low permeability coal seam was studied. A high pressure and stable sealing equipment was developed for uncorrected drilling in medium-hard and low permeability coal,overall hydraulic fracturing was adopted in mining coal seam based on directional long hole. The permeability enhancement mechanism of hydraulic fracturing for long borehole in mining coal seam was analyzed,and the strengthened permeability enhancement experiments of hydraulic fracturing were carried out.The hydraulic fracturing effect and influence scope were studied and evaluated by the variations comparison with the coal total moisture and borehole gas parameter during pre and post of hydraulic fracturing according to the change laws of fracturing parameters in the fracturing process. The results showed that he maximum injection pressure was up to 24. 60 MPa, the significant pressure drops occurred several times and the maximum pressure drop was 5. 2 MPa. The maximum impact radius of the fracture hole is 38 m and the average impact radius was over 30 m. The pure methane extraction volume increased 12. 70 times in average and the hectometer borehole gas drainage volume increased 2. 67 times in average,compared with the non fracturing drainage. The gas drainage efficiency was improved.