重庆三叠系碳酸盐岩热储热水水文地球化学特征

地下热水的水文地球化学特征研究有利于地下热水的开发,对重庆三叠系碳酸盐岩热储热水的研究可以更好地实现重庆地下热水的可持续开发。通过2009年1月和2009年7月对重庆市三叠系碳酸盐岩热储热水进行野外监测、取样和室内分析,发现重庆三叠系碳酸盐岩热储热水水化学性质相近,pH呈中性,水温30℃~50℃,电导率为1 320 μs/cm~3 250 μs/cm,水化学类型为SO₄-Ca(Mg)型,是典型的碳酸盐岩热储中-低温地下热水。温泉水的主要阳离子为Ca²⁺和Mg²⁺,阴离子为SO₄^2-和HCO₃^-,除青木关温泉外,SO₄^2-和Ca²⁺、Mg²⁺随时空变化较小,体现了碳酸盐岩中石膏与地下热水的水-岩作用对地下热水水文地球化学特征的控制。热水中的方解石和白云石都处于饱和与不饱和的临界状态,没有明显钙华沉积的现象;Na-K-Mg-Ca图解显示各个季节地下热水的物质来源基本一致,均没有达到水岩平衡状态。

HYDROGEOCHEMICAL FEATURE OF THERMAL GROUNDWATER IN CARBONATE RESERVOIR IN TRIASSIC IN CHONGQING

Study on the hydrogeochemical features of thermal groundwater is conducive to the exploitation of underground thermal water. Researches on the thermal groundwater in carbonate Reservoir in Triassic in Chongqing are expected to benefit Chongqing as the "Hot spring capital of the world" to achieving sustainable development of geothermal. In this study, samples of the thermal groundwater in carbonate reservoir in Triassic in Chongqing were obtained and tested in January and July in 2009. It was found that all the thermal water have similar features, such as being neutral in pH, with temperature ranging among 30℃ to 50℃, with high Electrical Conductivity (EC). These underground thermal water were defined as SO₄-Ca (Mg) type, which were identified to low-medium temperature geothermal water in carbonate reservoir. The major cations of these thermal water were Ca²⁺ and Mg²⁺ and the major anions were SO₄^2- and HCO₃^-. The concentration of SO₄^2-, Ca²⁺, and Mg²⁺ varied slightly with time but significantly among places, with an exception of two springs in Qingmuguan. These indicated that the hydrogeochemical properties of thermal groundwater in the study area are mainly controlled by the water-rock interaction, a process of water interaction with gypsum in carbonate rock. The calcite and dolomite of the underground thermal water are under the critical state of saturated to unsaturated, and there is no obvious phenomenon of travertine deposition. The Na-K-Mg-Ca diagram shows that the sources of the matters in thermal water in Carbonate Reservoir in Triassic in Chongqing are basically the same in each season and haven't reached the water-rock equilibrium.