An advanced CO2 gas-phase fracturing technology for efficient methane drainage, outburst prevention and excavation in outburst coal seam
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摘要: 我国煤矿煤与瓦斯突出灾害严重影响煤矿安全生产。尽管近10年来这一灾害事故大幅度减少,但恶性事故依然发生,给矿工生命和煤矿安全生产造成严重损失。国内外现阶段的防治瓦斯突出技术,如水力压裂、水力割缝、水力冲孔、深孔爆破、密集钻孔等,不同程度地解决了防突安全掘进,但对于一些高瓦斯低渗透突出煤层,上述技术还难以从根本上解决消突安全快速掘进。所以,防突技术仍然是我国煤炭领域亟待攻关的重大科技难题。选取山西寿阳县新元煤矿31002工作面为试验案例,介绍CO2气相压裂技术方法,并探讨其防突掘进效果。新元煤矿开采的山西组3号煤层为低渗透突出煤层,前期主要采用密集钻孔预抽瓦斯防突措施,抽采达标时间长,掘进速度慢。高效抽采瓦斯,防止煤与瓦斯突出,保障煤巷安全快速掘进,是新元煤矿安全高效生产的重大技术难题。在新元矿采取的气相压裂措施概况如下:在掘进工作面前方实施双钻孔气相压裂;完成9个瓦斯抽采钻孔以覆盖巷道两侧各15 m安全范围;全部11个钻孔联网抽采3~5 d,防突参数K1值达标后恢复掘进。试验数据表明,气相压裂抽采防突技术措施的强化抽采效果显著,抽采效率大幅度提高,煤炮等动力现象减少,K1值降低,掘进割煤时巷道瓦斯浓度得以降低和均化,保障了连续安全掘进。实践证明,CO2气相压裂技术能够实现连续安全快速掘进理技术,在全国类似瓦斯地质条件煤矿中具有推广应用意义。Abstract: Coal and gas outburst in coal mines is a serious disaster in China. Although the disaster has been reduced significantly over the past 10 years, vicious accidents still occure, causing serious losses to the lives of miners and the safety of coal mines. The current applied technologies for outburst prevention and control include hydraulic fracturing, hydraulic slitting, hydraulic flushing, deep hole blasting, intensive drilling, etc., which have solved the outburst problem and safe excavation in some degrees. Nevertheless, the above-mentioned technologies could not solve the problems of safety excavation in the high gas content and low permeability outburst coal seams. Therefore, preventing outburst technology is still a major difficulity in China's coal mines. The carbon dioxide gas fracturing and outburst elimination technology has been developed in Xinyuan Coal Mine of Shouyang County in Shanxi recently and has achieved good results. This paper introduces its technical characteristics, field test method and the effect of anti-burst excavation based on working face 31002 of Xinyuan Coal Mine. The No.3 coal seam of Shanxi Formation mined in Xinyuan Coal Mine is a low-permeability and outburst seam. In the early stage, intensive borehole drilling and gas pre-drainage were used to prevent gas outburst, which took a long time to reach the gas drainage standard, with a low excavation speed. Efficient gas extraction, prevention of coal and gas outbursts, and ensuring the safe and rapid excavation of coal roads are major technical problems for the safe and efficient production of Xinyuan Coal Mine. The key points of the CO2 gas fracturing technology are described as follows. Implementing 2 holes for CO2 gas-phase fracturing in front of the tunnel face and drilling additional 9 holes for gas drainage covering a safety range of 15 m in each side of the roadway. All the 11 boreholes were connected to the drainage network for 3-5 days, and the excavation resumed after the outburst prevention parameter K1 value reached the standard. The test data show that show that the CO2 gas fracturing significantly enhanced gas drainage efficiency and the coal cannon and other dynamic phenomena are reduced. With K1value reduced, the gas concentration in the roadway can be reduced and homogenized during coal cutting, ensuring a continuous safe driving. It is concluded that CO2 gas-phase fracturing can achieve high-efficiency gas extraction and prevention of outbursts, and it can be applied in coal mines with similar gas geological conditions across the country.
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表 1 密集钻孔防突掘进技术抽采情况
Table 1 Drainage situation using intensive drilling and anti-outburst tunneling technology
循环次数 打钻时间/d 抽采时间/d 瓦斯体积分数/% 日抽采量/m3 第1循环平均 10 17 19.0 481 第2循环平均 9 14 16.0 402 第3循环平均 8 14 17.0 429 平均值 9 15 17.3 437 表 2 密集钻孔防突掘进情况
Table 2 Tunneling situation using intensive drilling and anti-outburst tunneling technology
循环 掘进天数 K1最大值 K1平均值 卸压孔施工状况 第1循环平均 12 0.41 0.33 1次喷孔,4次压钻 第2循环平均 11 0.52 0.36 2次喷孔,4次压钻 第3循环平均 11 0.57 0.35 3次喷孔,5次压钻 平均值 11 0.35 表 3 气相压裂防突掘进技术抽采情况
Table 3 Drainage data using CO2 gas-phase fracturing technology
循环次数 打钻+压裂时间/d 抽采时间/d 瓦斯体积分数/% 日抽采量/m3 第1循环平均 7 5 39.3 1 010 第2循环平均 4 5 50.0 1 374 第3循环平均 4 5 55.0 1 534 平均值 5 5 48.1 1 306 表 4 气相压裂防突掘进技术掘进情况
Table 4 Tunneling data using CO2 gas-phase fracturing technology
循环次数 掘进天数 K1最大值 K1平均值 卸压孔施工状况 第1循环平均 8 0.38 0.31 1次压钻 第2循环平均 9 0.38 0.29 1次压钻 第3循环平均 7 0.37 0.33 未发生动力现象 平均值 8 0.31 表 5 CO2气相压裂前后绝对瓦斯涌出量对比
Table 5 Comparison of absolute gas emission before and after CO2 gas-phase fracturing
状态 日期 均值/(m3∙min–1) 最大值/(m3∙min–1) 方差/(m3∙min–1) 压裂前 第一天 1.45 2.98 0.158 1 第二天 1.56 3.70 0.610 6 第三天 1.88 3.50 0.923 8 压裂后 第一天 0.96 1.44 0.021 9 第二天 0.82 1.25 0.010 7 第三天 0.84 1.20 0.007 8 压裂前平均值 1.63 3.39 0.564 2 压裂后平均值 0.87 1.30 0.013 5 压裂后对比 降低13% 降低62% 降低98% 表 6 两种防突掘进技术的主要技术参数对比
Table 6 Comparison of the main technical parameters of two anti-outburst tunneling technologies
瓦斯治理技术 全部时间/d 掘进时间/d 抽采时间/d 绝对瓦斯涌出量平均值/(m3∙min–1) 绝对瓦斯涌出量最大值/(m3∙min–1) K1最大值 动力现象次数 日均进尺/m 密集钻孔技术 106 34 45 1.6 3.4 0.57 19 4.17 气相压裂技术 54 24 15 0.9 1.3 0.38 2 6.25 对比 节约52 d 节约10 d 节约30 d 降低0.7 降低2.1 降低0.19 减少17次 提高50% -
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