碳酸盐结垢对中低温地热流体回灌的影响——以咸阳地热田为例

应用水文地球化学模拟和室内模拟耦合方法，对引起地热尾水回灌堵塞的问题进行研究。结果显示，回灌过程中化学结垢的主要类型为碳酸盐。影响碳酸盐堵塞的因素主要为温度、C02脱气、混合程度、pH以及矿化度。随着温度、pH、C02分压的增大CaC03结垢趋势增加；当360％的原水和40％的尾水混合时，CaC03的沉淀量达到最大；而矿化度的影响主要体现在盐效应和同离子效应。运用朗格利尔指数和雷兹诺指数对CaCO3沉淀程度进行计算，结果表明，在研究区内多数井中存在中低程度的CaCO3结垢。

The Effect of Carbonate Scale on the Reinjection of Geothermal Effluent at Low/Middle Temperature-A Case Study of Geothermal Field in Xianyang

The paper tries to find out the obstacle for geothermal effluent reinjection by simulating the hydro - geochemistry of geothermal fields in Xianyang and establishing coupling model in lab. The result indicates that carbonate scale, the forma- tion of which are mainly affected by temperature, CO2 degassing, mixing degree and mineralization,is the leading factor in im- peding geothermal effluent reinjection. Moreover, higher temperature, PH and partial pressure of CO2 will make CaCO3 scale formation easier. When mixing ratio of raw geothermal fluid and geothermal effluent is to 60% to 40% , the precipitation vol- ume of CaCO3 will reach the peak while mineralization affects the strength of salt effect and common ion effect. Lastly, the pa- per calculates the Langelier index and Ryznar index of CaCO3 precipitation in studied wells. The results show that CaCOz scale more or less exist in most wells located on geothermal field in Xianyang.