依据北京市不同地热田80 组地热水和地下水样品水化学测试结果分析, 地热水化学类型自北部山区向南部 平原依次可划分为SO42Na 型、H CO32Na 型和Cl2Na 型水, 中间又有各过渡带水化学类型, 而沉积盆地通常是 H CO32Na 型地热水; 地热水中一些特殊组分如氟、偏硅酸、偏硼酸、硫化氢等含量显著高于常温( 冷) 地下水。进一 步分析认为, 北京地热水是由外部圈层冷水在入渗补给过程中经过增温形成的; 地热水的组分比率受到蒸发浓缩或 冷水稀释的影响较小, 冷热水的混入程度不同仍会导致组分比发生变化; 各地热田中地热水绝大部分属于未成熟 水, 热水中水2岩之间尚未达到离子平衡状态。计算表明, 北京地热田K2Mg 温标的计算温度为38. 1 e ~ 136. 6 e , SiO2 温标的计算温度在57. 4 e ~ 154. 2 e 之间, 而实测温度多为22. 0 e ~ 118. 5 e , 估算温度与实测温度的对比 可反映钻探可及温度与地热水曾经达到的温度, 因此可以为地热勘探提供依据。

Based on the chemical analy sis on 80 g eo thermal w ater and g ro undwater samples, the geo chemical ty pes of the g eo2 therma l w ater va ry fr om SO42Na in the nort her n mo untain ar ea, H CO32Na in Beijing Depression, and to Cl2Na in the souther n edg e o f Beijing Plain. The co ncentrat ions of F- , SiO3 2- , BO2 - , and H2 S in g eothermal water are hig her than those in cold gr oundwat er. Further analy sis sug g ests that t he geo thermal w ater is formed by t he temper ature increasing of peripheral cold water during the infilt ration pr ocess. The results show that eva po ratio n concent ratio n and co ld water dilution have insig nificant effects on the component r atios o f Na/ K, Cl/ F, Cl/ B, and Cl/ SiO2 ; how ever, the mix ing degr ee betw een co ld and hot water can affect t he rat ios. M ost of the g eothermal w ater is immature, and the w ater2r ock inter action has not reached io n balance. The cal2 culated K2M g g eothermomet er temperature r ang es f rom 38. 1 to 136. 6 e , the calculated quartz temperature ranges fr om 57. 4 to 154. 2 e , and the well head temper atur e o f g eothermal w ater ranges from 22. 0 t o 118. 5 e . The compar ison between the cal2 culated and measur ed temperatures r ef lects the temperatur e which the bo re can r each and the hig hest temper atur e of the g eo2 therma l w ater. The results can pro vide the hy dr og eochem ical evidence fo r g eothermal water exploitat ion in Beijing.

中国地质调查局/ 全国地热资源调查评价2北京市地热资源现状调查评价与区划0 项目( 水[ 2013] 012 0292006)