CO2相变致裂技术在顺煤层钻孔增透中的应用

摘要

In order to improve the gas drainage effect in the soft,low permeability and high gassy seam under the karst geology condition,based on Guizhou Lyutang Mine as the study object,the seam pressure released and permeability improved technology with a CO2 phase change fractured borehole drilling along the seam was provided.The paper had an analysis on the seam failure characteristics under the splitting effect of the CO2 fracturing transient gas,including the crack unstability and diffusion characteristics and the high pressure wave splitting mechanism.The results of the permeability improved test with the CO2 fractured borehole drilling along the seam showed that the permeability effect of the CO2 fracturing borehole drilling technology along the seam was obvious,after the fracturing in the area,the seam permeability was increased by five times and the attenuation coefficient was reduced by 53.6％.The gas drainage concentration was increased by three times and the average drained gas volume fraction was about 70％.Under the condition of the same gas drainage time,the residual gas content in the seam was obviously reduced and the gas drainage rate was about 55％.In No.6 medium seam of the Mine,the period of the previous gas drainage target was about 6～12 months and after the fracturing,the period of the gas drainage target was 1 ～2 months.The overall gas drainage efficiency was increased by six times and the period of the gas drainage target was highly reduced.%为了提高喀斯特地质条件下松软低透高瓦斯煤层的瓦斯抽采效果,以贵州绿塘煤矿为研究对象,提出了煤层CO2相变致裂顺层钻孔卸压增透技术,分析了CO2致裂瞬间气体尖劈作用下煤体的破坏特点、裂隙的失稳扩散特点及高压波劈裂机理.CO2致裂顺层钻孔增透试验结果表明:CO2致裂顺层钻孔技术增透效果明显,该区域致裂后煤层透气性提高5倍,衰减性系数降低了53.6％;瓦斯抽采浓度增大3倍,平均抽采瓦斯体积分数约为70％,在抽采时间相同的情况下煤层残余瓦斯含量显著降低,抽采率约为55％,该煤矿6中煤层原来抽采达标周期为6～12个月,致裂后抽采达标周期为1～2个月;整体抽采效率提高了6倍,抽采达标周期大幅缩短.