天津地区深层地下热水井水动力特征

Dynamic Features in Deep Geothermal Wells in Tianjin Area

天津地区部分深层地下热水钻井在开采过程中井口水温明显高于开采前的井口水温,井内水的密度随之降低,可导致动水位高于开采前的静水位。采取井底压力的折算公式和室内实验的方式分别对实测数据和该现象进行分析、模拟。结果表明,开采条件下的井底压力明显小于停采条件下的井底压力,水位拟合主要受地热井的密度、井底压力的计算公式和计算方法、地质结构以及地热井回灌等因素的影响;在实验第一阶段观测到井底温度与井口水位呈正线性相关,井底压力与水柱的平均密度呈线性负相关;在第三阶段平均密度和井底压力也呈线性负相关;而在第二阶段井底压力几乎保持不变时,可以根据该压力对不同井口温度时动水位升高值进行预测。

The wellhead temperature of part of deep geothermal wells in Tianjin in the pumping process is higher than the water temperature before pumping and the density of thermal water decreases,which result in the dynamic water level higher than the static water level prior to pumping.In this paper,the conversion formula of well bottom pressure is adopted to analyze the measured data and a laboratory test is established to simulate the regular pattern of water level of a thermal well.The dynamic water level and static water level can approximately be calculated according to the average well bottom pressure during pumping and the stopping pumping conditions last year.The results show that in pumping condition the well bottom pressure is smaller than that prior to pumping and the water level is mainly affected by the number of geothermal wells,the calculating formula of the well bottom pressure,geological structure,geothermal injection and other factors.In the first stage the experiment shows that in the well bottom water temperature and wellhead temperature change linearly.Well bottom pressure and the average density are negatively correlated.In the third stage well bottom pressure and the average density are also negatively correlated.In the second stage bottom hole temperature changes very little,the bottom hole pressure remains almost unchanged.Therefore,according to the pressure the dynamic water level of different wellhead temperature can be predicted.