低透气性煤层减漏增透综合增抽技术

为了解决低透气性煤层的煤层气抽采难题,以山西王家岭煤矿2号低透气性煤层为例,首先对不同封孔长度下煤层气的抽采进行了数值模拟,然后进行抽采钻孔封孔工艺改进及CO_2相变爆破增透数值模拟,进而开展了综合增抽技术的现场试验。研究结果表明:①延长封孔长度可减少巷道中空气渗漏量,王家岭矿2号煤层抽采钻孔合理封孔长度为12 m;②增加封孔长度、采用固液耦合壁式封孔工艺可有效减少巷道漏风量,同时提高煤层气抽采浓度和抽采纯量;③CO_2相变爆破后钻孔壁大面积破损,并形成很多相互交织的爆生裂隙和开口较大的孔洞,距离爆破点3 m处的渗透率为初始渗透率的5倍,距离爆破点4 m处的渗透率为初始渗透率的1.6倍;④减漏增透综合增抽技术应用后,煤层气抽采纯量提高了200倍。结论认为,由增加封孔长度、固液耦合壁式封孔工艺、CO_2相变爆破增透所构成的煤层减漏增透综合增抽技术,可以有效地破解低透气性煤层煤层气抽采的难题,现场应用效果良好。

A comprehensive extraction enhancement technology of reducing leakage and improving permeability in low-permeability coal seams

In this paper, the No.2 low-permeability coal seam of Wangjialing Coal Mine was taken as an example to study how to solve the problem of coalbed methane (CBM) extraction in low-permeability coal seams. Firstly, the extraction of CBM at different sealing lengths was numerically simulated. Then, the extraction drilling and sealing process was improved, and the CO2 phase change blasting for permeability improvement was numerically simulated. Finally, this comprehensive extraction enhancement technology was tested on site. And the following research results were obtained. First, extending the sealing length can reduce the air leakage in the roadways, and the reasonable sealing length of the No. 2 coal seam is 12 m. Second, increasing the sealing length and adopting the solid–liquid coupling wall-type sealing technology can effectively reduce the air leakage in the roadways and increase CBM extraction concentration and net CBM production. Third, after the CO2 phase change blasting, the borehole wall was extensively damaged, and many intertwined explosion-induced cracks and large pores were formed. The permeability at 3 m from the blasting point is 5 times the initial permeability, and that at 4 m from the blasting point is 1.6 times. Fourth, after this comprehensive extraction enhancement technology was applied, the net CBM production was increased by about 200 times. In conclusion, this comprehensive extraction enhancement technology consisting of sealing length increasing technology, solid–liquid coupling wall-type sealing technology and CO2 phase change blasting technology for e leakage reduction and permeability improvement can effectively solve the problem of CBM extraction in low-permeability coal seams, and its on-site application results are good.