基于统计方法评价沁水盆地南部煤层气开采对地下水环境的影响

Statistical Evaluation of Impact of Coalbed Methane Exploitation on Groundwater Environment in Qinshui Basin

针对沁水盆地煤层气开采对地下水环境的影响问题,基于统计学方法对采集的129件水样进行分析,系统评价了地下水与煤层气排采水之间的关系。Piper三线图对各含水层地下水和煤层气排采水水化学特征的分析表明,沁水盆地区域地下水常见离子以HCO3-、SO42-、Ca2+、Mg2+为主,煤层气排采水水化学类型以HCO3-、Cl-、Na+为主,与地下水水化学类型差异大。箱式图结果表明:煤层气排采水中F-平均质量浓度远高于区域地下水中的,可选取F-作为煤层气排采水的示踪剂;沁水盆地未出现地下水F-质量浓度大范围升高现象,仅柿庄区块南部水样(1027-4、1027-5)和郑庄区块(1030-3)东南部水样地下水出现高F-质量浓度。通过聚类分析评价地下水和煤层气排采水之间的F-质量浓度关系,结果显示:柿庄区块南部煤层气排采水F-质量浓度与Na+、HCO3-、Fe3+质量浓度相关性好,水样1027-4同时出现Na+、HCO3-、Fe3+偏高现象;郑庄区块东南部煤层气排采水F-与NO3-质量浓度相关性好,但1030-3未出现NO3-质量浓度偏高现象。结果表明:沁水盆地煤层气开采未造成大范围地下水污染,但柿庄区块南部局部地区浅层地下水混入煤层气排采水。

Aiming at the impact of coalbed methane(CBM) exploitation on groundwater environment in Qinshui basin, a total of 129 water samples were collected and analyzed by statistical methods, and the relationship between groundwater and CBM co-produced water was systematically evaluated. The hydrochemistry characteristics were analyzed by Piper diagram. The main ions of groundwater are HCO3-, SO42-, Ca2+, and Mg2+, and those of the CBM co-produced water are HCO3-, Cl-, and Na+. The types of hydrochemical characteristics of groundwater and CBM co-produced water are quite different. The average concentration of F-in CBM co-produced water is higher than that in groundwater, so F-could be treated as a tracer of CBM co-produced water. The concentration of F-in groundwater did not increase in regional, however, the water samples from Shizhuang block South(1027-4, 1027-5) and Zhengzhuang block Southeast(1030-3) showed high F-. The relationship of F- from CBM co-produced water and groundwater was analyzed by cluster analysis. The cluster analysis results show that F- from CBM co-produced water in Shizhuang block South has a good correlation with Na+, HCO3-, and Fe3+, and the concentration of Na+, HCO3-, and Fe3+ from 1027-4 is higher than that in the surrounding area. F- from CBM co-produced water in Zhengzhuang block Southeast has a good correlation with NO3-, however, the concentration of NO3- from 1030-3 is not higher than the surrounding value. It is shown that CBM exploitation does pollute the groundwater in regional, while in the Shizhuang block, the shallow groundwater is polluted by CBM co-produced water.