大兴矿煤层气井排采水化学特征分析

Analysis of chemical characteristics of drainage water from coalbed methane wells in Daxing coal field

以大兴矿煤层气井排采水为研究对象,在常规化学离子测试结果的基础上,分析了排采水的化学成分特征及时空演化特征,探讨了煤层气井产能与水中各化学成分的关系。研究表明:大兴矿煤层气井排采水为弱碱性或碱性咸水,HCO3-与Na+是水中质量浓度最大的离子;采样时间内,排采水已经进入稳定阶段,主要为原始地层水;各构造部位煤层气井排采水的化学特征存在差异,反映了不同构造部位地下水径流强度与交替程度强弱不同;不同构造部位煤层气井产能随TDS,HCO3-质量浓度增大而呈现出增大、减小两种相反的变化趋势,表明水文地质和构造地质作用对产能有很大影响;各井产能随CO32-质量浓度增大而减小,说明排采水的化学特征受碳酸平衡作用的调节。

Taking the drainage water from coalbed methane(CBM) wells in Daxing coal field as research object, this study describes the characteristics of chemical composition and spatial-temporal evolution and explores the relationship between the productivity of CBM wells and the chemical components based on the chemical test results of it. The results show that the drainage water is weak alkaline or alkaline saline. HCO3-and Na+are the ions with the highest concentration in the drainage water. During the sampling period, the drainage water has been in the stable stage which is basically the original formation water. There are differences in chemical characteristics of drainage water from CBM wells in different structural locations, and it reflects that the degree of groundwater runoff and alternation is various. The productivity of CBM wells in different structural locations increases or decreases with the increase of concentration of TDS and HCO3-, showing that hydrogeology and tectonics have great influence on productivity.The productivity of each well decreases with the increase of concentration of CO32-, which indicates that the chemical characteristics of the drainage water are regulated by the balance of carbonate.