封闭不良天然气孔突水过程的水文地球化学特征

Hydrogeochemical characteristics during water inrush of poorly sealed gas hole

为了查清封闭不良天然气孔突水过程中充水水源的变化规律,开展了气孔出水水文地球化学特征研究。结果表明:"大53"天然气孔突水过程中TDS浓度逐渐降低,初期为SO_4·Cl—Na型水,位于Piper三线图右端部,来自直罗组;中期TDS浓度降至500多mg/L,属于HCO_3·SO_4·Cl—Na型水,位于Piper三线图右端偏下,来自白垩系;期间煤层底部涌出高TDS的SO_4·Cl—Na型水,该水样点位于三线图右端偏上。气孔处理过程中,水样中γ(Ca)/γ(Na)系数均远大于其他水样,且HCO_3~–未检出,为煤层顶板直罗组水化学特征,表明阻隔了2-1煤层与白垩系含水层和2煤—6煤含水层的水力联系。取距离阈值20,分层聚类分析可以将水样分为白垩系水和侏罗系水,距离阈值5又可将侏罗系含水层水细分为直罗组2段、直罗组1段和2煤—6煤含水层水,实现了对气孔突水过程中充水水源变化规律的准确判别。

In order to make clear the water-filling source of Hulusu coal mine during water inrush of poorly sealed gas hole,some evaluation methods（e.g.,piper three wire drawing,hierarchical clustering law） were used to analysis the hydrogeochemical characteristics of water samples.The results showed that the concentration of TDS decreased gradually.During Initial stage of water inrush,water was of SO_4·Cl—Na type and located at the right end of piper three wire drawing and came from Zhiluo Formation.During the middle stage of water inrush,the concentration of TDS decreased to about 500 mg/L.The sampling points were located at the lower right end of piper three wire drawing,water was of HCO_3·SO_4·Cl—Na type and came from Cretaceous System.During water inrush,water of SO_4·Cl—Na type with high TDS gushed out from seam bottom,the water sampling points,the sampling points were located at the upper right end of piper three wire drawing.During treatment of gas hole,γ（Ca）/γ（Na） coefficient in the water was much higher than that of other water samples,and HCO_3~– was not detected,the water had hydrochemical characteristics of Zhiluo Formation water in seam roof,showing that the hydraulic connection between seam 2-1 and Cretaceous aquifer and seams 2–6 aquifers was cut off.Taking 20 as distance threshold value,hierarchical clustering analysis could divide the water samples into Cretaceous water and Jurassic water,and the distance threshold 5 may divide further the water of Jurassic aquifer into water of second member and first member of Zhiluo Formation,water of seams 2–6 aquifers,realizing accurate discrimination of the variation law of water-filling source during water inrush of gas hole.