Abstract:

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.

Key words: dynamic water level, well bottom pressure, fitting of water level, thermal groundwater, Tianjin