酸化对高阶煤不同层理方向增透效果影响研究

Study on the effect of acidification on the increase of permeability in different seam directions of high rank coal

为了研究酸化对寺河矿高阶煤垂直、平行两个层理方向的增透效果,开展了多组分酸煤粉和煤柱溶蚀试验,优选出了合适的酸液体系,分析了两个层理方向煤柱不同酸化时长下的溶蚀效果,并进行了两个层理方向煤柱的煤岩三轴吸附-解吸-渗流试验和低场核磁共振试验,对比了酸化前后的渗透率、孔隙度、孔径分布变化。结果表明:(1)寺河矿酸化选用质量分数2%HCl+2%CH3COOH+5%HF的酸液配比溶蚀效果最优;(2)酸化使垂直层理方向煤柱的孔隙率增幅更大,而平行层理方向煤柱达到最大增幅用时更短;(3)酸化后两个层理方向煤柱的渗透率、孔隙度均提升,垂直层理方向煤柱孔隙度增幅更大,渗透率增幅则小于平行层理方向煤柱,且二者的渗透率增幅都在滑脱效应拐点处最小;(4)酸化使两个层理方向煤柱的瓦斯吸附孔占比下降,其中平行层理方向煤柱降比更大,且酸化前后中大孔占比也都更高;确定了寺河矿酸化后以煤样平行层理方向作为钻孔瓦斯抽采方向能更好地提高瓦斯抽采率。

In order to study the effect of acidification on the permeability enhancement of high rank coal in Sihe Mine in vertical and parallel bedding directions,This study carried out the dissolution tests of multi⁃component acid pulverized coal and coal column,optimized the appropriate acid solution system for acidification,and analyzed the acidification dissolution effect of coal column in two bedding directions under different acidification duration.And triaxial adsorption desorption seepage experiment and low field nuclear magnetic resonance experiment of coal and rock of coal pillars in two bedding directions before and after acidification were carried out,and the changes of permeability,porosity and pore size distribution of coal pillars in two bedding directions before and after acidification were compared.The results show that:(1)After the dissolution experiment of pulverized coal,it is found that the acid solution ratio of 2%HCl+2%CH3 COOH+5%HF has the best dissolution effect;(2)After the coal column dissolution experiment,acidification makes the porosity of coal column in the vertical bedding direction increase more than that in the parallel bedding direction,and the coal column in the parallel bedding direction can reach the maximum increase faster;(3)After acidification,the permeability and porosity of coal pillars in the vertical and parallel bedding directions are increased.The former has a larger increase in porosity,but the increase in permeability is less than the latter,and the increase in permeability of coal pillars in the two bedding directions is the smallest at the inflection point of slippage effect;(4)By comparing the pore size distribution of coal pillars in the two bedding directions before and after acidification,it is found that acidification reduces the proportion of gas adsorption pores in coal pillars in the two bedding directions,and the proportion of coal pillars in the parallel bedding direction is greater,and the proportion of medium and large pores before and after acidification is higher;It is determined that after acidification in Sihe Mine,the direction of coal sample parallel to bedding is taken as the direction of gas drainage in borehole,which can better improve the gas drainage rate.