地热开发对王3、王4井水化学动态的影响及其原因分析

ANALYSIS ON EFFECT AND CAUSE OF WATER CHEMISTRY BEHAVIOR IN WANG-3 AND WANG-4 WELLS DUE TO GEOTHERMAL EXPLOITATION

王3、王4井是首都圈地区两口重要的水化学观测井,京津新城地热开发对王3、王4井有无影响,对震情监视有重要意义。依据2004年7月后京津新城地热开发与王3、王4井井压急剧下降,氡、汞等测项相应变化的相关分析,认为尽管地热开发的含水层和地震观测层位不同、埋深不同,但地热开发仍然是影响王3、王4井地震观测的根本原因。从地质构造、岩溶裂隙的发育、水动力条件及地下水物理-化学平衡等方面,论述了地热开发对王3、王4井水化学动态影响的原因,并在此基础上对地热异常区内水化学观测井选择、建设的有关问题提出了建议。

Wang-3 and Wang-4 wells are two important wells for water chemistry observation in the Capital region. Whether or not the geothermal mining in Jingjinxincheng has influence to the two wells is of great significance to seismic regime monitoring. In this paper,based on the correlatability analysis of sharp pressure drop and water radon and water mercury changes caused by geothermal exploitation in Wang-3 and Wang-4 wells after July 2004 in Jingjinxincheng,we find that geothermal exploitation is the root cause of affecting earthquake observation in Wang-3 and Wang-4 wells despite different horizons and depths of geothermal aquifer and earthquake observation. Then, the author analyses the factors that influence the water chemistry behavior in Wang-3 and Wang-4 wells due to geothermal mining from the aspects of geological structure, development of Karst fissure, under-ground hydrodynamic condition, heat-dynamical condition ,physical-chemistry equilibrium of underground water, and so on. Furthermore, the author puts forward some suggestions about site selection and construction of water chemistry observation well in geothermal anomaly area.