煤层瓦斯抽采顺层钻孔偏斜规律及原因分析

Analysis on Deviation Rule and Cause of Gas Extraction Borehole along Seam in Coal Seam

顺层钻孔抽采煤层瓦斯是矿井常用消突措施之一,但钻孔偏斜造成的消突空白带又给安全生产带来新的隐患。为了查明钻孔偏斜规律及原因,采用赤平投影及MATLAB滤波处理,再结合统计分析的方法,分别建立倾角-进尺、方位角-进尺2种数学模型。研究表明,顺层钻孔轨迹的倾角随钻进深度的增加总体是一个长周期或若干短周期。进尺小于50 m时,钻孔轨迹沿煤层向下偏斜,进尺大于50 m后,钻孔轨迹先向下偏斜,后向上发生偏斜;钻孔轨迹的方位角的变换呈左右摇摆的周期性变化,第1周期起始偏移的方向(向左或向右)总是向着地层的真倾向方向靠近,随进尺深度的增加周期变短。根据分析,造成钻孔偏斜主要原因为岩层产状、施工工艺和孔壁间隙等。

Gas extraction in coal seams by bedding is one of the common outburst measures in mines.However,the blanking gap caused by borehole deflection brings new hidden dangers to safety production.In order to find out the rule and cause of borehole deflection,use the stereographic projection,MATLAB filtering processing and mathematical analysis method,then establish two mathematical models of inclinationdepth and azimuth-depth. The research shows that the dip angle of the borehole track is generally a long period or several short periods with the increase of drilling depth. When the drilling depth is less than 50 m,the borehole axis deviates downward along the coal seam. After the drilling depth is more than 50 m,the borehole axis deviates downward first, and then upward. The azimuth angle of the borehole track changes periodically with the swaying of left and right. The direction of the initial migration of the first cycle(left or right) is always close to the true orientation of the formation,and the period becomes shorter with the increase of the drilling depth. According to the data analysis,the main causes of bedding borehole deflection are rock formation, construction technology,hole wall clearance and so on.