深孔定点快速取样技术在钻屑瓦斯解吸指标K 1值测试中的应用

Application of quick sampling technology in deep hole at fixed point to test K_(1) value of drilling cuttings gas desorption index

钻屑瓦斯解吸指标K_(1)值是综合反映煤层瓦斯含量及卸压初期瓦斯解吸速度大小的指标,是确定煤层局部突出危险性程度的关键参数,对煤与瓦斯突出灾害防治具有重要作用。本文针对煤矿采用麻花钻杆机械排渣取样法,取样测试K_(1)值过程中存在的无法准确确定取样位置和煤样暴露时间、有效测试深度浅、现场测值与实际情况误差较大等问题,利用基于反循环钻进原理研发的深孔定点快速取样技术及装置对K_(1)值合理有效取样测试深度进行研究。研究结果表明:深孔定点快速取样技术利用双壁钻杆的中心管将钻孔底部煤样快速排出,所取煤样中未掺混钻孔壁上的煤粉,达到了定点取样的要求,保证了测定煤样的有效性,且取得足够数量的煤样时间不超过2 min,有效减少了煤样的暴露时间,可以有效提高K_(1)值的有效测定深度及测定结果的准确性,在仲恒煤矿和湾田煤矿采用深孔定点快速取样技术可增加钻屑解吸指标K_(1)值有效测试深度至30 m。

The K_(1) value of drilling cuttings gas desorption index is an index that comprehensively reflects the gas content of coal seam and the gas desorption speed at the initial stage of pressure relief.It is a key parameter to determine the risk degree of local coal seam outburst,and plays an important role in preventing and controlling coal and gas outburst disasters.This paper aims at the problems existing in the process of sampling and testing K_(1) value by using the sampling method of mechanical slag discharge of the drill pipe in coal mine,such as the inability to accurately determine the sampling location and exposure time of coal sample,the shallow effective testing depth,and the large error between the field measurement value and the actual situation.The reasonable and effective sampling depth of K_(1) value is studied by using the deep hole quick sampling technology and equipment developed based on the reverse circulation drilling principle.The results show that the deep-hole fixed-point rapid sampling technology uses the central pipe of the double-wall drill pipe to discharge the coal sample at the bottom of the borehole quickly.The coal powder on the borehole wall is not mixed in the coal sample,which meets the requirements of fixed-point sampling and ensures the effectiveness of coal sample measurement.In addition,the time of obtaining sufficient number of coal samples is less than 2 min,which effectively reduces the exposure time of coal sample.The effective measurement depth of K_(1) value and the accuracy of measurement results can be effectively improved.The effective testing depth of K_(1) value of drill cuttings desorption index can be increased to 30 m by using deep hole quick sampling technology in Zhongheng Coal Mine and Wantian Coal Mine.