胶东典型花岗岩热储地下热水水化学特征及热储研究

招远地热田位于胶东隆起区，元古代蚀变花岗岩分布广泛，地下热水微量元素丰富。为查明地下热水微量组分的赋存条件、花岗岩热储环境与地热资源量，利用地下热水水化学分析、热储分析及有效能源换算法，建立Gibbs模型，进行PHREEQC模拟并开展热储估算。研究结果显示：（1）地下热水水化学类型为Cl—Na型，与海水水化学类型一致，地下热水溶解性固体总量（TDS）介于1359.7~5302.0 mg/L，锶、溴、偏硅酸等微量组分的质量浓度分别达26.20，7.50，88.00 mg/L，均超过国家医疗热矿水水质标准；（2）地热田东北方向的玲珑花岗岩中锶的质量分数较高，介于334~1 805 mg/kg，是地下热水中锶的一个重要来源；（3）热储温度在107~215 °C之间，硅-焓图解法分析冷水混入比例为33.6%~58.9%。结果显示：40~60 °C的总可用能源19.73 TJ/a，总热能达5479.57 MW·h，吨油当量471.16 toe；>60 °C的总可用能源301.57 TJ/a，总热能达83771.53 MW·h，吨油当量为7203.06 toe。综合分析认为研究区地热资源丰富，地下热水微量组分来源于花岗岩热储层的溶滤作用，富集过程受热储环境的影响，研究结果有助于完善地下热水水-岩相互作用理论。

A study of the hydrochemical characteristics and geothermal water of typical granite geothermal reservoir in the Jiaodong area

Zhaoyuan is located in Jiaodong uplift zone. Proterozoic altered granites are widely distributed. The trace elements are enriched in geothermal fields. In order to ascertain the occurrence conditions of the trace components, the granite geothermal reservoir and geothermal resources. We use hydrochemical analysis, reservoir temperature analysis and effective energy conversion methods, establish Gibbs model, PHREEQC model, reservoir estimation, and obtain the occurrence conditions and reservoir environment of trace components of thermal water. The results show that (1) Zhaoyuan geothermal water, similar to seawater, is Cl—Na type. The total dissolved solids (TDS) of geothermal water ranges from 1359.7 mg/L to 5302.0 mg/L, and the mass concentrations of strontium, bromine and metasilicic acid are 26.20, 7.50 and 88.00 mg/L, respectively, which exceed the national medical thermal mineral water quality standards. (2) The Linglong granite in the northeast of the geothermal field has high strontium content, ranging from 334 mg/kg to 1 805 mg/kg, which is an important source of strontium. (3) The reservoir temperature of geothermal field is between 107 °C and 215 °C, and the mixing proportion of cold water is between 33.6% and 58.9% calculated from silicon enthalpy diagram. The calculation results indicate that available energy is 19.73 TJ/a, 5479.57 MW·h and 471.16 toe between 40 and 60 °C. The total available energy is 301.57 TJ/a, 83771.53 MW·h, and 7203.06 toe over 60 °C. The trace components come from lixiviation between strontium-rich granite surrounding rock and groundwater. The enrichment process of trace elements is affected by geothermal reservoir. This study may provide a better understanding of the characteristics of geothermal water in the granite thermal reservoirs, and enrich and promote the theory of geothermal water-rock interactions.