“三软”低透煤层高压注氮促抽瓦斯工程实践

Engineering test of high pressure nitrogen injection for gas drainage in"three soft"low permeability coal seam

为提高“三软”低渗透煤层的瓦斯抽采效果,在郑煤集团赵家寨煤矿井下采用注入高压纯氮气(组分为97%)的方法进行强化注抽煤层瓦斯试验。试验结果表明,在注气压力为1.5 MPa时,注气影响半径为2 m,影响范围内的排放瓦斯孔混合流量增加了9~21.8倍,纯瓦斯流量增加了4.2~6.2倍;井下穿层钻孔注气+抽采工艺措施的现场考察结果表明,抽采孔混合流量的增长幅度与注气压力呈正比关系,长时边注边抽的注抽效果好于间歇注抽效果,在6 MPa压力下,注气有效半径为6 m;注气35 d后煤层瓦斯含量降低了25.38%,煤中解吸的气体组分中,CH 4浓度由97.12%下降到79.06%,氮气浓度由0.94%增加到12.38%。对比了同样范围长时边注边抽措施和水力割缝措施钻孔工程量、瓦斯治理费用以及预抽瓦斯达标时间等参数。

In order to improve the gas drainage effect of the"three soft"low permeability coal seams,an industrial test of enhanced injection and drainage of coal seam gas was conducted by the method of high-pressure pure nitrogen injection(97%composition)in the Zhaojiazhai Coal Mine of Zhengzhou Coal Industry Group.The test results showed that when the injection pressure was 1.5MPa,the influence radius of gas injection was 2 m,the mixed gas flow and pure gas flow of the gas drainage hole within the influence range increased by 9-21.8 times and 4.2-6.2 times respectively;the field investigation results of the gas injection and drainage technology measures in the borehole through the formation showed that the increase of the mixed flow rate of gas drainage hole was proportional to the gas injection pressure,and the effect of long-term injection and drainage was better than that of intermittent injection and drainage,under the pressure of 6 MPa,the effective radius of gas injection was 6 m;after 35 days of gas injection,the gas content in coal seam decreased by 25.38%,the concentration of CH 4 in the gas component desorbed from the coal decreased from 97.12%to 79.06%,and the nitrogen concentration increased from 0.94%to 12.38%.The drilling quantity,gas control cost and gas pre-drainage time of long-time injection and drainage measures and hydraulic slotting measures in the same range were compared.