摘要
为探讨广安市铜锣山背斜三叠纪岩溶热储特征、地热水水化学与同位素组成、热储温度及地热水循环机理,采用地热钻探、水化学与同位素取样测试、热水溶质组分图解分析等手段和方法,开展了地热水成因的研究工作。结果表明:研究区三叠纪碳酸盐岩热储结构相对完整,热储盖层、热储层和热储下部隔水层形成独立的地热水文地质单元。岩溶地热水水化学类型主要为SO_(4)-Ca·Mg和SO_(4)-Ca型,富含F、Sr、Li、B和SiO_(2)物质,其水源补给为大气降水,补给区位于铜锣山以北的大巴山一带,深部地热水补给高程大于1100 m,补给区年均温度为9℃。热储温度为56~76℃,热水循环深度为2013~3030 m。地热水在循环过程中,主要发生碳酸盐岩和蒸发岩溶解、冷热水混合过程,且冷水混入比例大于80%。结合区域地热地质条件,构建了研究区地热水成因概念模型。
There are abundant geothermal resources at low-medium temperature in the fold mountain areas of eastern Sichuan,and the main geothermal reservoirs are Leikoupo and Jialingjiang formations.Generally,karst geothermal reservoirs have the advantages of large water volume,easy reinjection of tail water after exploitation,and less damage to geothermal reservoirs.Recently,a great breakthrough in geothermal exploration of the Tongluo mountain anticline in fold mountain areas of eastern Sichuan has been achieved.Two deep geothermal wells with a depth of more than 1,700 m have been consecutively drilled to obtain karst geothermal resources with high development and utilization value.However,although good results have been obtained in terms of geothermal exploration,there are relatively few studies on the characteristics of geothermal reservoirs and the mechanism of geothermal water circulation.In the study on structure characteristics of Triassic karst geothermal reservoir,geothermal water chemistry and stable isotope composition,geothermal reservoir temperature,and mechanism of geothermal water circulation,methods including geothermal drilling,hydro-geochemistry,diagram analysis of thermal water components,and geo-thermometer assessment are used to analyze the occurrence condition of karst geothermal water and genetic model in this study area.Results show that the geothermal reservoir structure in the study area is relatively intact,and the cap layer of thermal reservoir,the thermal reservoir,and the lower water barrier layer are formed as independent geothermal hydrogeological units.Karst geothermal water is mainly SO_(4)-Ca·Mg and SO_(4)-Ca types and rich in contents of F,Sr,Li,B,and SiO_(2).The oxygen and hydrogen isotope analysis indicates that karst geothermal water is of meteoric origin,and the recharge area is located in the Daba mountainous area to the north of Tongluo mountain.The elevation of deep geothermal water recharge is more than 1,100 m;the average annual temperature of the recharge area is 9℃;the horizontal distance reaches 220 km.According to the SiO_(2) geo-thermometer,the karst geothermal reservoir temperature is 56-76℃;the circulation depth of geothermal water is 2,013-3,030 m,and the karst geothermal water is immature.Moreover,the dissolution of carbonate and evaporite and the mixing of cold groundwater are major hydro-geochemical processes in the geothermal water circulation path,and the mixing ratio of cold groundwater is higher than 0.8.Based on the results of geothermal geology,geothermal drilling,hydro-geochemistry,and environment isotopes,the genesis mechanism of geothermal water in this area is summarized as follows,groundwater receives water recharge from rainwater through karst depressions,sink,and pit of the Leikoupo and Jialingjiang formations in the anticline core region,heated by geothermal gradient and hot rock during the deep circulation of the anticline wing.During water circulation,major hydro-geochemical processes are water-rock interaction and thermal-cold water mixing.After then,karst geothermal water occurs along the anticline axis and wing region in forms of hot springs and geothermal wells.This study not only enriches the theory of the karst geothermal reservoirs system in the fold mountainous areas of eastern Sichuan but also provides a scientific basis for the exploration and exploitation of deep karst geothermal resources in this area.
作者
袁建飞
刘慧中
邓国仕
李明辉
YUAN Jianfei;LIU Huizhong;DENG Guoshi;LI Minghui(Chengdu Center of China Geological Survey,Chengdu,Sichuan 610081,China)
出处
《中国岩溶》
CAS
CSCD
北大核心
2022年第4期623-635,共13页
Carsologica Sinica
基金
中国地质调查局项目《西南诸河澜沧江流域水文地质与水资源调查》(DD20211381)
《四川广安资源环境综合地质调查》(DD20190524)
中国地质调查局成都地质调查中心科技基金《川西高原高温地热流体特征组分的水文地球化学研究》(KJ201867)。
关键词
铜锣山背斜
岩溶热储结构
地热水成因
水文地球化学
广安市
Tongluo mountain anticline
the structure of karst geothermal reservoir
geothermal water genesis
hydrogeochemistry
Guang’an City
