Technology of gas extraction by deep hole directional drilling in underground coal mine and its applicatio
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摘要: 为解决试验矿井采用传统抽采技术存在巷道掘进速度慢、采掘接替紧张的问题,提出采用深孔定向钻进瓦斯抽采技术施工定向长钻孔替代常规钻孔进行煤层瓦斯抽采的方案。定向钻进对煤层有效作用面积大,可以大范围改变煤体原始应力的分布,从而打破煤层瓦斯吸附-解吸的动态平衡,使大量吸附态瓦斯转化为游离态;在钻孔负压与煤体地应力和瓦斯压力形成的压力梯度作用下,游离态瓦斯源源不断地流向钻孔空间,使周围煤体瓦斯得到有效排放,煤体发生收缩变形,透气性系数大幅增加,地应力与瓦斯压力梯度减小,从而使得定向长钻孔抽采影响范围扩大,实现煤层瓦斯大面积有效抽采。试验结果表明:采用深孔定向钻进技术施工定向长钻孔成孔良好,试验钻孔总进尺为2 213 m,主孔最大孔深达523 m,日均抽采纯量为3 528 m3;钻孔平均瓦斯抽采体积分数高达88.3%,最高为98.0%;单孔平均瓦斯抽采纯量为1.23 m3/min,最大超过2 m3/min,瓦斯抽采效果显著;与常规钻孔抽采相比,定向钻孔单孔瓦斯抽采纯量提高了16倍多,单孔瓦斯抽采体积分数提高了2~4倍,巷道月均进尺提高了1倍多。Abstract: In order to solve problems of slow tunneling and tension of mine excavation replacement in test mine using traditional extraction technology, a scheme of using deep hole directional drilling with long directional drilling instead of conventional drilling to carry out coal seam gas extraction was proposed. Directional drilling has a large effective area on coal seam, which can change distribution of original coal stress in a large range, thus breaking dynamic balance of gas adsorption and desorption in coal seam and transforming a large number of adsorbed gas into free state; Under the action of pressure gradient formed by drilling negative pressure and coal ground stress and gas pressure, free gas flow continuously to drilling space, make the surrounding coal gas emission effectively, cause shrink deformation of coal, permeability coefficient increases significantly, ground stress and gas pressure gradient are reduced, so as to make the long drilling directional extraction influence range expanded, realize the effective gas extraction from coal seam in a large area. The test results show that using deep hole directional drilling with long directional drilling can get a well formed hole and has obvious effect in gas extraction. Total drilling footage of the test hole is 2 213 m,the maximum drilling depth reaches 523 m, and the average daily extraction pure quantity is 3 528 m3. The average volume fraction of gas extraction is up to 88.3%, and the highest value is 98.0%. The average single-hole gas extraction pure quantity is 1.23 m3/min, and the maximum value exceed 2 m3/min. Compared with conventional drilling extraction, the pure quantity of single-hole gas extraction of directional drilling is increased by more than 16 times, the volume fraction of single-hole gas extraction is increased by 2-4 times, and monthly average footage of roadway is increased by more than1 times.
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