太平庄观测井地下流体动态综合研究

SYNTHETIC STUDY OF THE DYNAMIC BEHAVIOR OF UNDERGROND FLUID IN TAIPINGZHUANG WELL

太平庄观测井是一口有十几年观测资料并有几次较好震例的综合观测井。近年来 ,由于地下水的大量开采 ,使得地下水位大幅度下降 ,尤其是观测井周围地热的开采 ,对太平庄观测井的正常动态影响较大。文中结合往年较正常的动态特征和地质构造等 ,分析了太平庄观测井的水位、水温、逸出气和断层气等的年动态变化特征。结果表明 :水位、水温的变化规律受观测井水位补给区降雨量的影响 ,水温还受当地降雨量的影响 ,特别是太平庄观测井周围新井的抽水对水温、水位、逸出气均有一定影响。由于观测井受诸多因素的影响 ,导致太平庄观测井的观测资料不能按往年的变化规律进行动态分析。在排除了降雨和人为的干扰因素外 。

Taipingzhuang observation well is one of the wells that has been observed for over ten years and has experienced some earthquake cases.In recent years,the ground water level has significantly fallen due tolarge amount exploitation of underground water,and especially geothermal exploitation around the Taip-ingzhuang observation well.This paper presents the analysis of the annual behavior of water level,water temperature,escaped gases and fault gases of the Taipingzhuang observation well,on the basis of the nor-mal behavior in former years and the tectonic setting of the well.The analysis shows that the variation of water level and water temperature depends on the rainfall at the recharge area of the well,and the variation of water temperature is affected also by local rainfall.Especially,the withdrawal of newly drilled wells around the observation well greatly affects the variation of water level,water temperature and escaped gases of the observation well.After eliminating the effects of rainfall and human factors,the observed data of the Taipingzhuang well will still be useful for the prediction of seismic regime in Beijing region. After eliminating interference factors,the water level and water temperature of Taipingzhuang well for the year of2002was consistentwith the normal annual behavior of the well,and no significant anomalywas observed.The water level in2002was lower in winter and higher in summer and autumn,in consistence with the ordinary annual behavior of the well.However,the rise of water level of the well after the end of heating period in spring was very slow,and the risen water level was4m lower than the highest level in the same period of2001.This might be attributed to the pervasive water level drop in Beijing region,and es-pecially to the large amount exploitation of hot water around Taipingzhuang area. H 2 content of the escaped gases in the Taipingzhuang observation well begins to increase anomalously with the withdrawal of hot water in winter,and than decreases to normal value at the end of heating period in March.This phenomenon can be attributed to the following reasons:The large amount exploitation of hot water causes the significant drop of water level,which in turn causes the decrease of pore pressure in the layer;in this condition the gases will expand and H 2 may remove rapidly,causing the increase of H 2 con-tent in escaped gases.In addition,the gases from the depth are concentrated mainly in the space above the aquifer,and the drop of water level will cause the escape of these stored gases,and hence the increase of H 2 content.