广东省丰良地热田高氟地热流体成因及热储温度评价  

Genesis of geothermal fluid with high fluorine content and reservoirtemperature assessment in Fengliang geothermal field, eastern Guangdong

作　　者：李义曼[1,2,3] 罗霁 陈凯 黄天明[1,2,3] 天娇[6] 程远志 LI Yiman;LUO Ji;CHEN Kai;HUANG Tianming;TIAN Jiao;CHENG Yuanzhi(Key Laboratory of shale gas and geoengineering,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,100029;Innovation Academy for Earth Science,Chinese Academy of Sciences,Beijing,100029;University of Chinese Academy of Sciences,Beijing,100049;State Power Investment Corporation Research Institute,Beijing,102209;China University of Mining and Technology(Beijing),Beijing,100083;Institute of Earthquake Forecasting,China Earthquake Administration,Beijing,100036)

机构地区：[1]中国科学院地质与地球物理研究所页岩气与地质工程重点实验室,北京100029 [2]中国科学院地球科学研究院,北京100029 [3]中国科学院大学,北京100049 [4]国家电投集团科学技术研究院有限公司,北京102209 [5]中国矿业大学(北京),北京100083 [6]中国地震局地震预测研究所,北京100036

出　　处：《地质论评》2023年第4期1337-1348,共12页Geological Review

基　　金：国家重点研发计划课题(批准号:2019YFC0604901);自然科学基金重点项目(批准号:42072328)的成果~~。

摘　　要：广东丰顺丰良地区出露的地热水温度高达96℃,热储层为裂隙发育的下侏罗统的英安斑岩,F^(-)含量较高。但关于其地热流体的补给来源、循环演化过程及热储温度研究较少。笔者等基于早期开展的勘探工作和补充采集、测试的地热水和气体数据,探讨了该地热系统的流体成因及热储温度。结果表明,丰良地区地热水存在2类,A类地热水温度普遍低于40℃,Ca^(2+)含量高,Na^(+)和K+含量低,以HCO_(3)^(-)—Ca^(2+)型为主;B类地热水Na^(+)含量高,Ca^(2+)含量低,为HCO_(3)^(-)—Na^(+)型。A类地下水可能受浅层地下水混入影响,但缺少直接证据。B类地下水由周边山区的大气降水补给,沿裂隙或者断裂系统进入英安斑岩储层,循环深度和水—岩相互作用时间分别可达5200~6300 m和22 ka;储层温度条件下铝硅酸盐矿物的溶解以及阳离子交换作用促进了富N_(2)、SiO_(2)、F^(-)、Na^(+)、Sr和Li的地热水的形成;深部地热水上升至地表过程中,受冷水混入(混入比例为10%~25%)及少量CO_(2)脱气(蒸汽散失比例为0.3%~0.5%)的影响;F^(-)含量受控于富氟副矿物萤石矿物的溶解,与温度和pH值成正比。基于校正了混合作用和CO_(2)脱气作用的地温计组合方法,得到深部热储温度为138~143℃,与其南部的汤坑地热系统热储温度一致,二者有可能属于同一大的地热系统。Objectives:Geothermal water occurring in Fengliang area of Guangdong province has temperature as high as96℃ and it is found in the fractured prophyrite of the lower Jurassic period. Fluorine concentration is high ingeothermal water and has caused food poisoning before. This paper is intended to study the recharge sources,circulation and evolution of the geothermal fluid with high fluorine content and possible reservoir temperature forfuture sustainable development. Methods: Geothermal water and local surface water were collected for water and gas chemical and isotopicanalysis. In addition, geochemical simulations to compute the fluorine species and saturation index of certainminerals were also applied. For reservoir temperature calculation, geothermometers with mixing and degassingcorrection were used based on geochemical processes occurring from deep to surface. Results:There are two types of geothermal water. A type geothermal water is of HCO_(3)^(-) —Ca^(2+) type with highconcentration of Ca and low concentration of Na and K and temperature is below 40℃. B type geothermal water isof HCO_(3)^(-) —Na^(+) type with high concentration of Na and K and low concentration of Ca and temperature is higher than40℃. The fluorine content is about 15. 0 ~ 22. 6 mg/ L. Geothermal gas is dominated by N_(2) and also containsseldom CO_(2), Ar and O_(2), indicating the sources of air and crust. Conclusions: A type geothermal water may be affected by mixing of shallow groundwater but evidences weremissing. B type geothermal water is the deep geothermal fluid. It is recharged by the local mountains and infiltratesthrough fractures to porphyrite reservoir and the circulation depth and water—rock interactions time can achieve5200~6300 m and 22 ka. Dissolution of the alumino-silicate minerals and cation exchange promote the formation ofgeothermal fluid with high concentration of N_(2), SiO_(2), F, Na, Sr and Li. During the ascending processes, mixingby Hanjiang River water (mixing ratio is about 10%~25%) and slightly CO_(

关 键 词：丰良地热田 流体循环 阳离子交换 混合作用 氟 热储温度 

分 类 号：P314[天文地球—固体地球物理学]