关中盆地蓝田—灞河组地热水化学特征及形成机制  

Hydrochemical characteristics and formation mechanism of Lantian-Bahe Formation geothermal water in Guanzhong Basin

作　　者：夏岩[1] 张莹 郭路[1] 任战利[2,3] 高文冰 兰华平[2] 陈凯 祁凯[2,3] 侯亚云[1] 邢光远 XIA Yan;ZHANG Ying;GUO Lu;REN Zhanli;GAO Wenbing;LAN Huaping;CHNE Kai;QI Kai;HOU Yayun;XING Guangyuan(Exploration and Development Research Institute of PetroChina Changqing Oilfield Company,Xi’an 710018,China;Department of Geology,Northwest University,Xi’an 710069,China;Key Laboratory of Exploration and Development of Multiple Energy Resources,Xi’an 710069,China)

机构地区：[1]中国石油长庆油田分公司勘探开发研究院,西安710018 [2]西北大学地质学系,西安710069 [3]西安市多种能源资源勘探开发重点实验室,西安710069

出　　处：《非常规油气》2023年第4期1-11,21,共12页Unconventional Oil & Gas

基　　金：国家重点研发计划项目“未固结砂岩热储层保护与增效钻完井技术及材料”设立的专题“不同地区典型未固结砂岩热储层特征及评价”(2019YFB1504201-01);长庆油田分公司勘探开发研究院合作项目“关中盆地地热资源调查及开发技术政策研究”。

摘　　要：采用水化学及同位素分析等方法对关中盆地蓝田—灞河组水文地球化学特征及形成机制进行了研究。结果表明:研究区地热水以Cl—Na和Cl—SO_(4)—Na—Ca型水为主,地热流体水化学由浅到深,从HCO_(3)·SO_(4)—Na型→SO_(4)·HCO_(3)—Na型→SO_(4)·Cl—Na型→Cl·SO_(4)—Na型→Cl—Na型,水化学类型由单一型向复合型过渡,最终演变为单一型Cl—Na型。研究区热储层温度较高,分布范围较宽,为40~105℃,大部分水样温度高于60℃,平均温度为72.8℃。pH值均大于7,属于弱碱性水;TDS(矿化度)普遍高于1 g/L。地下热水14 C年龄在7000~28000 a之间,从盆地南北两侧向中部逐渐变老,在盆地南北两侧存在地表水的补给。盆地中部新生界孔隙裂隙型地热流体的赋存环境相对封闭,盆地形成过程中早期地层的部分地下水由于新生代地层的快速沉降和堆积而在孔隙中封存,随着盆地的不断沉降和堆积,逐渐加压和封存了孔隙中的地下水。The hydrogeochemical characteristics and formation mechanism of Lantian-Bahe Formation in Guanzhong Basin were studied by hydrochemistry and isotope analysis.The results show that the geothermal water in the study area is dominated by Cl—Na and Cl—SO_(4)—Na—Ca water,and the hydrochemistry of geothermal fluid changes from shallow to deep,from HCO_(3)·SO_(4)—Na type→SO_(4)·HCO_(3)—Na type→SO_(4)·Cl—Na type→Cl·SO_(4)—Na type→Cl—Na type.The hydrochemistry type changes from single type to complex type,and finally evolves into single type Cl—Na type.The temperature of the thermal reservoir in the study area is relatively high,with a wide distribution range of 40~105℃.The temperature of most water samples is higher than 60℃,and the average temperature is 72.8℃.pH is greater than 7,belonging to weakly alkaline water;TDS is generally higher than 1 g/L.The age of underground hot water 14 C is between 7000 to 28000 a,and it gradually gets older from the north and south sides of the basin to the central part.There is downward recharge of surface water in the north and south sides of the basin.The occurrence environment of the Cenozoic pore-fissure geothermal fluid in the middle of the basin is relatively closed.During the formation of the basin,due to the rapid settlement and accumulation of the Cenozoic strata,part of the groundwater in the early strata is sealed in the pores.With the continuous settlement and accumulation of the basin,the groundwater in the pores is gradually pressurized and sealed.

关 键 词：地热水 水化学 形成机制 蓝田—灞河组 关中盆地 

分 类 号：P314[天文地球—固体地球物理学]