Hydrogeochemistry and Origin of Thermal Groundwater in Bedrock Aquifers in Tianjin, China

Thermal groundwater resources were found to have occurred in deep-seated bedrock aquifers in the northeastern North China plain near Tianjin, China. Meso- to Neo-Proterozoic and Paleozoic carbonate rocks on the Cangxian uplift are capable of yielding 960-4 200 m 3/d of 60 to 96 ℃ water from the wells ranging in depth between 1 000 and 4 000 m. Conductive heat flow of 0.063 to 0.144 2 W/m 2 from the deep crust is responsible for this anomalous geothermal field. The water in the Ordovician aquifer is characterized by relatively high TDS, high concentrations of SO 4 and SO 4·Cl-Na·Ca type, but the waters from the Meso- to Neo-Proterozoic and Cambrian aquifers, by relatively low TDS, low concentrations of SO 4 and predominantly Cl·SO 4-Na type. It is noted that when the temperature of the waters increases at a rate of 10 ℃ in the range of 30-100 ℃, the content of SiO 2 increases at a rate of 12 to 15 mg/L, and fluoride concentration increases at a rate of 2.3 to 2.5 mg/L. Hydrochemical and isotopic data suggest that the thermal water in the bedrock aquifers is of meteoric origin and recharged in the northern mountain area to the north of the Baodi-Ninghe fault, and then flows laterally for a long distance from the north to the south to the city of Tianjin. Temperature of the waters increases because of heat exchange with the rocks and recharge by conductive heat flow from beneath.

Arrangement Strategy of Ground Heat Exchanger with Groundwater

The orientation strategy of side pipe and the heat transfer performance of six ground heat exchangers(GHEs) were optimized by numerical simulation,with soil being treated as a porous medium.An experiment on the heat transfer of four GHEs was carried out in 2010.Results indicate that the velocity field is disturbed by GHEs.The optimal orientation strategy of side pipe is that the upward pipe is located upstream and the downward pipe downstream.The space between GHEs should be appropriately adjusted,depending on the direction and flow velocity.Groups of GHEs should be installed perpendicular to the mainstream in a single row,but if the acreage does not meet the requirements,GHEs should be installed in staggered multiple rows.Fewer GHEs parallel to the mainstream strengthen the heat transfer.Moreover,numerical results agree well with the test data,with the maximum relative error being less than 7.7%.

Hydro-geochemical simulation of the mixing balance of exploitation and reinjection of geothermal fluid

This paper targets its research at the exploitation–reinjection well of geothermal fluid of one geothermal heating project in Tianjin, China, examines such factors as ground temperature, CO_2 partial pressure and stratum lithology, and simulates the changes in the main component contents of geothermal fluids mixed at different proportions in the exploitation and reinjection well. The research findings show that the mixed fluids are increasingly similar in nature to the reinjected water as the reinjection process goes on. It's suggested that the manual method should be used to ensure the reinjected water has the similar mineralization as the exploited ground water in the process of reinjection and some acceptable adjustments should be made according to the specific component and water temperature. The study on water-rock balance calculation shows that PHREEQC can simulate the complicated chemical reactions related to water when the transfer of solute happens, so the necessary technological supports are given for the reasonable development and protection of geothermal resources.

A hydrochemical study of the Hammam Righa geothermal waters in north-central Algeria

This study focuses on the hydrochemical characteristics of 47 water samples collected from thermal and cold springs that emerge from the Hammam Righa geothermal field, located in north-central Algeria. The aquifer that feeds these springs is mainly situated in the deeply fractured Jurassic limestone and dolomite of the Zaccar Mount. Measured discharge temperatures of the cold waters range from 16.0 to 26.5 ℃ and the hot waters from 32.1 to 68.2 ℃. All waters exhibited a near-neutral pH of 6.0-7.6. The thermal waters had a high total dis- solved solids （TDS） content of up to 2527 mg/l, while the TDS for cold waters was 659.0-852.0 mg/l. Chemical analyses suggest that two main types of water exist： hot waters in the upflow area of the Ca-Na-SO4 type （Ham- mam Righa） and cold waters in the recharge zone of the Ca-Na-HCO3 type （Zaccar Mount）. Reservoir tempera- tures were estimated using silica geothermometers and fluid/mineral equilibria at 78, 92, and 95℃ for HR4, HR2, and HRI, respectively. Stable isotopic analyses of the δ18O and δD composition of the waters suggest that the thermal waters of Hammam Righa are of meteoric origin. We conclude that meteoric recharge infiltrates through the fractured dolomitic limestones of the Zaccar Mount and is conductively heated at a depth of 2.1-2.2 km. The hotwaters then interact at depth with Triassic evaporites located in the hydrothermal conduit （fault）, giving rise to the Ca-Na-SO4 water type. As they ascend to the surface, the thermal waters mix with shallower Mg-rich ground- water, resulting in waters that plot in the immature water field in the Na-K-Mg diagram. The mixing trend between cold groundwaters from the recharge zone area （Zaccar Mount） and hot waters in the upflow area （Hammam Righa） is apparent via a chloride-enthalpy diagram that shows a mixing ratio of 22.6 〈 R 〈 29.2 %. We summa- rize these results with a geothermal conceptual model of the Hammam Righa geothermal field.

Validation of basaltic glass adsorption capabilities from geothermal arsenic in a basaltic aquifer: A case study from Bjarnarflag power Station,Iceland

Arsenic is a carcinogen known for its acute toxicity to organisms.Geothermal waters are commonly high in arsenic,as shown at the Bjarnarflag Power Plant,Iceland (w224 mg/kg of solvent).Development of geothermal energy requires adequate disposal of arsenic-rich waters into groundwater/geothermal systems.The outcome of arsenic transport models that assess the effect of geothermal effluent on the environment and ecosystems may be influenced by the sensitivity of hydraulic parameters.However,previous such studies in Iceland do not consider the sensitivity of hydraulic parameters and thereby the interpretations remain unreliable.Here we used the Lake Myvatn basaltic aquifer system as a case study to identify the sensitive hydraulic parameters and assess their role in arsenic transport.We develop a one-dimensional reactive transport model (PHREEQC ver.2.),using geochemical data from Bjarnarflag,Iceland.In our model,arsenite (H3AsO3) was predicted to be the dominant species of inorganic arsenic in both groundwater and geothermal water.Dilution reduced arsenic concentration beloww5 mg/kg.Adsorption reduced the residual contamination below w0.4 mg/kg at 250 m along transect.Based on our modelling,we found volumetric input to be the most sensitive parameter in the model.In addition,the adsorption strength of basaltic glass was such that the physical hydrogeological parameters,namely: groundwater velocity and longitudinal dispersivity had little influence on the concentration profile.

Characteristics of shallow geothermal fields in major cities of Tibet Autonomous Region

Based on the project titled "Investigation and evaluation of shallow geothermal energy in major cities of Tibet Autonomous Region", the distribution characteristics and occurrence conditions of shallow geothermal fields in these cities were introduced in this paper. To this end, relevant data in Lhasa, Shigatse and Nyingchi Cities through vertical thermometry was a focus, so as to analyze groundwater temperature and the distribution law of strata with constant temperature. Then through comprehensive comparisons and analysis of the relationship between groundwater temperature and climate, differences in this aspect of Nagqu City were taken as a typical case to clarify formation of geothermal field and corresponding influence on groundwater temperature, furthermore providing basic data for rational development and utilization of shallow geothermal energy in Tibet Autonomous Region.

Mass balance of saline lakes considering inflow loads of rivers and groundwater: the case of Lake Issyk-Kul, Central Asia

This study aimed to elucidate the influence of inflow water on the salinity concentration process of a saline lake and the mass balance of Lake Issyk-Kul,a tectonic saltwater lake in Kyrgyzstan.Based on the survey results and meteorological data from 2012 to 2015,we analyzed the dissolved chemical composition loads due to water inflow.Then,we discussed the relationship between the increase in salinity and water inflow into the lake.Through the water quality analysis data,we used the tank model to estimate the river inflow and analyze the loads by the L-Q curve.The groundwater loads were then estimated from the average annual increase in salinity of the lake over a period of 30 a.The results suggest that Lake Issyk-Kul was temporarily freshened between about AD 1500 and 1800 when an outflowing river existed,and thereafter,it became a closed lake in AD 1800 and continued to remain a saline lake until present.The chemical components that cause salinization are supplied from the rivers and groundwater in the catchment area,and when they flow into the lake,Ca^(2+),HCO_(3)−and Mg^(2+)precipitate as CaCO_(3) and MgCO_(3).These compounds were confirmed to have been left on the lakeshore as evaporite.The model analysis showed that 1.67 mg/L of Ca^(2+)and Mg^(2+)supplied from rivers and groundwater are precipitated as evaporite and in other forms per year.On the other hand,salinity continues to remain in the lake water at a rate of 27.5 mg/L per year.These are the main causes of increased salinity in Lake Issyk-Kul.Since Na^(+)and Cl^(-)are considered to be derived from geothermal water,they will continue to flow in regardless of the effects of human activities.Therefore,as long as these components are accumulated in Lake Issyk-Kul as a closed lake,the salinity will continue to increase in the future.

A NEW APPROACH TO IDENTIFY GROUNDWATER ACTIVITY BY USING GEOTHERMAL DATA

The effect of groundwater activity on the regional geotemperature pattern and heat flow measurements is one of the frontier topics in modem geothermal studies. It is well known that groundwater activity exists everywhere in the uppermost part of the Earth’s crust. However, this activity sometimes seems very difficult to identify during temperature

大型地埋管群地源热泵三维传热-渗流耦合模拟

为确定地下水渗流对大尺度、多分支埋管集群地源热泵系统换热区温度场和换热特性的影响,基于上海天文馆880个地埋管地源热泵场地,建立考虑地下水渗流和地质分层的三维传热-渗流耦合模型,并利用现场热响应试验对模型进行验证。结果表明:渗流作用引起管群内和支管群之间沿地下水流动方向发生温度干扰,89.5~120.3 m埋深范围内的温度干扰现象相对明显;地下水渗流有利于提高管群的换热总量,缩小夏季和冬季工况的换热量差距;换热量增加百分比随水力梯度的增加而增大,两者呈对数函数关系,当水力梯度大于0.005时,换热量增加百分比趋于平稳。

冀中坳陷岩溶热储地下水对流活动的聚热效应

地形起伏及浮力均可以驱动地下水流,在此过程中通过对流方式快速传递热量,进而改变温度分布模式,造成局部显著热异常,对岩溶储层地热资源聚敛有着重要意义.冀中坳陷岩溶热储发育,岩溶缝洞系统为地下水提供了良好的垂向和水平径流条件,形成了独特的对流-传导复合型地热系统.通过温度场、水动力场耦合数值模拟,本文聚焦冀中坳陷岩溶热储强迫对流和自由对流联合作用模式及其聚热效应.二维有限元数值模拟结果表明,在自由对流模型的基础上,地形驱动的强迫对流叠加作用使岩溶层内地下水流速显著增加.地形驱动流体可以推动自由对流单元向坡下滚动,强化了地下水对流的聚热效应.高阳凸起和献县凸起显著的热异常主要归因于岩溶储层和断裂带内地下水自由对流的传热效应,基底起伏造成的热流折射聚热效应是次要的.此外,地形驱动下,自由对流单元向流域下游方向推进可能是献县凸起较高阳凸起热异常更为显著的重要原因.

北京小汤山地区第四系高氟地下水与地热水关系研究

北京小汤山地区第四系深层地下水氟含量普遍超标,严重制约区域供水。在收集整理基础地质、水文地质、地热地质资料基础上,开展第四系高氟地下水与地热水之间关系研究工作。研究表明:小汤山地区位于复式背斜的核部区域,该区热储层与第四系地层直接接触并形成水力“天窗”,受构造应力影响在热储层发育大量张性裂隙,加之上覆第四系盖层结构松散且厚度较薄,导致该区成为地热富集带;在高温高压环境下,地热水中氟化物含量普遍较高,地热水上涌同第四系深层地下水发生热流-冷流的混合作用,导致第四系深层地下水中氟化物含量升高,形成第四系高氟地下水。

硼同位素分馏及其在地下水研究中的应用进展

硼(B)在自然界水体和岩石中广泛存在,B的2种稳定同位素(10B和11B)相对质量差较大,因此B同位素容易产生明显的分馏。在不同水文地质环境下,地下水往往具有不同的B同位素组成(δ^(11)B),研究地下水B同位素组成及变化,对认识水文地球化学过程以及合理开发地下水资源具有重要的指导意义。文章在介绍B同位素分馏原理的基础上,归纳了吸附/共沉淀作用、解吸附作用、风化作用、蒸发作用等水文地球化学过程对地下水δ^(11)B值的影响。较为系统地梳理了B同位素技术在地下水研究中的应用成果:(1)由于污染源和海水的δ^(11)B值往往与地下水背景值存在明显差异,因此可利用B同位素示踪地下水污染与海水入侵;(2)不同矿物δ^(11)B值的差异和风化条件的差异会显著影响地下水δ^(11)B值,通过B同位素能反映矿物的风化特征、识别地热水与围岩相互作用过程;(3)地下水B同位素还能用于示踪与氟、砷富集相关的水文地球化学过程,从而完善高氟、高砷地下水的形成机理。在此基础上,分析了B同位素技术在地下水研究中的应用潜力:(1)将B同位素技术与水化学方法及其他同位素技术相结合,量化不同水文地球化学过程对目标组分迁移转化的贡献;(2)对富B地热水、天然劣质地下水地区进行B同位素长期监测,确定不同环境条件下的地下水B端元,定量评估有害组分对环境造成的负面影响。这些科学问题的解决不仅能推动B同位素技术在地下水研究中的进一步发展,还有助于提高对地下水有害组分形成机制的整体认识。

天津市馆陶组热储集中开采区热储压力恢复原因分析

地热是一种清洁能源,局部集中开采会形成压力降落漏斗。【研究目的】天津地区由于地热开发历史长,形成了大范围压力降落漏斗。2018年开采量逐步减少后,漏斗中心地带的水位开始迅速回升,热储压力开始恢复。但水位回升与开采量变化的相关关系、漏斗形态会发生哪些变化,目前研究较少,发展规律认识不够清晰。【研究方法】本文以天津地区新近系馆陶组热储层采灌条件下多年水位动态变化特征为例,通过采灌量和水位的相关关系分析,研究漏斗区水位动态演化规律,分析压力恢复的原因,并给出漏斗区地热可采量评价的合理建议。【研究结果】研究认为热储水量持续“入不敷出”是水位降落漏斗形成的根本原因,而群井抽水叠加效应导致热储压力的同步波动,消耗量骤减和漏斗的夷平作用使得漏斗中心区域水位回升。【结论】地热评价和管理应以漏斗区域内热储压力的实时动态为基准,合理控制消耗量,维持水量收支平衡,是地热资源持续利用的有效途径。

泰山北翼岩溶含水介质分布及地下水循环规律研究

为了深入认识济南岩溶泉水及地热水循环过程,本文以泰山北翼碳酸盐岩含水介质空间分布特征为研究出发点,分析其埋藏条件和连续性特征,并利用数理统计、空间插值、Piper三线图、概念模型等方法,结合水动力场、水化学场、水温度场和水年龄场“四场”分析,揭示区域地下水循环规律。结果表明:地表分水岭与齐广断裂、禹王山断裂、聊考断裂等深大断裂控制了泰山北翼地区岩溶含水介质空间展布,大致呈现由南向北埋藏深度逐渐增大的变化趋势,受马山断裂、东坞断裂、文祖断裂等次级断裂影响岩溶含水介质上下盘有不同错动,但东西展布仍具有较好连续性;区域地下水循环过程极其复杂,泰山岩群、寒武纪及奥陶纪各类含水岩组通过排泄-渗漏、断裂垂向径流、水平地下径流等形式发生水流交汇,并在山前局部地区与第四纪松散孔隙水产生水量交换,最终通过泉或人工开采形式排泄。区域地下水流具有统一的“四场”,并且呈现明显的水平与垂向分带特征,大致沿东阿断裂及其延长线—吴家堡—华山—章丘区—淄博磁村一线划分冷泉与地热水的分界线,以600 m、1000 m划分出浅、中、深循环深度分界线;冷泉以浅循环为主,中、深循环为辅,地下水矿化度、温度、年龄偏低,而地热水以中、深循环为主,浅循环为辅,地下水矿化度、温度、年龄偏大。不同含水介质水流具有一定内在关联,构成一个完整的岩溶水系统。

Geochemical and Hydrogeochemical Processes Determining Arsenic Presence in Rocks and Groundwater in the Southeastern Portion of El Bajío Guanajuatense,Guanajuato,Mexico

Several aquifers located in North-Central Mexico have natural arsenic(As)concentrations higher than those allowed by national and international regulations;these aquifers are usually located in fractured volcanic environments that interact with sedimentary basins and have a carbonate basement.In this study,an evaluation of As in volcanic and sedimentary rocks collected at 13 sampling sites along the Sierra de Codornices(Guanajuato State,Central Mexico)was carried out.These geologic materials are representative of the dominant hydrogeologic environment.The As content is disseminated in volcanic rocks and the highest contents were obtained in felsic rocks;this information served to identify the hydrogeochemical processes related to the mobilization and transport of arsenic in the aquifer.The mobilization of As is a product of the dissolution of volcanic glass,a process involved in the alkaline desorption that occurs on As-containing mineral surfaces and possibly by the dissolution/desorption of Fe minerals and some clays,all these processes may be accelerated by the geothermal characteristics of the groundwater in the study area.

Planning and construction of Xiong’an New Area(city of over 5 million people):Contributions of China’s geologists and urban geology

China established Xiong’an New Area in Hebei Province in 2017,which is planned to accommodate about 5 million people,aiming to relieve Beijing City of the functions non-essential to its role as China’s capital and to expedite the coordinated development of the Beijing-Tianjin-Hebei region.From 2017 to 2021,the China Geological Survey(CGS)took the lead in multi-factor urban geological surveys involving space,resources,environments,and disasters according to the general requirements of“global vision,international standards,distinctive Chinese features,and future-oriented goals”in Xiong’an New Area,identifying the engineering geologic conditions and geologic environmental challenges of this area.The achievements also include a 3D engineering geological structure model for the whole area,along with“one city proper and five clusters”,insights into the ecology and the background endowment of natural resources like land,geothermal resources,groundwater,and wetland of the area before engineering construction,a comprehensive monitoring network of resources and environments in the area,and the“Transparent Xiong’an”geological information platform that is open,shared,dynamically updated,and three-dimensionally visualized.China’s geologists and urban geology have played a significant role in the urban planning and construction of Xiong’an New Area,providing whole-process geological solutions for urban planning,construction,operation and management.The future urban construction of Xiong’an New Area will necessitate the theoretical and technical support of earth system science(ESS)from various aspects,and the purpose is to enhance the resilience of the new type of city and to provide support for the green,low-carbon,and sustainable development of this area.

济源-开封凹陷东段馆陶组热储水化学特征及成因启示

对济源-开封凹陷东段馆陶组地热水进行分析研究发现,其水化学性质为中性水、盐水、极硬水,以Cl-Na型水为主,其化学特征、控制因素、特征系数等与上部明化镇组地热水、第四系地下水及地表水差异明显.馆陶组地热水为陆相含盐岩地层沉积型溶滤水,赋存介质为砂岩孔隙,区域发育的断裂、裂隙为其提供导热和运移的通道,在大地热流的传导增温下,不断发生溶滤作用、蒸发浓缩作用等,同时热储层封闭性良好,热水运移较停滞,还原性彻底,浓缩程度高.开封断隆内馆陶组地热水的以上特征与开封-兰考断陷相比程度更高.

氢氧稳定同位素的研究进展及在地热流体运移演化中的应用

地热流体作为地下水循环系统的重要组成部分,具有较强的经济价值和社会意义,而氢氧稳定同位素是认识水循环系统的重要信息指标,其组成特征可揭示区域内地热流体运移演化过程的规律变化,对掌握区域内地热流体补给来源,认清地热水循环路径具有重要作用,进而对合理开发利用保护地热资源提供理论支撑具有重要意义。现阶段,常利用丰度、同位素比值(R值)、千分偏差值(δ值)及氘盈余和17O盈余等变量来表示氢氧稳定同位素组成特征,并通过与标准品等参照物的比对,分析氢氧稳定同位素的变化规律及趋势,从而判断海洋水、大气水汽和降水、江河、湖泊水及地下水循环系统中氢氧稳定同位素区域性的演化分异特点,进而分析水循环系统所处温度、湿度、地质条件特征;明确其补给来源及补给比例;判断系统内水蒸发量、滞留时间等要素。而地热流体作为地下水循环系统的一部分,其氢氧稳定同位素的相关研究仍有不足,应加强针对地热流体氢氧稳定同位素的研究,认清其与区域内其他水循环系统的关系,同时注意引用新参数,应用新方法,并坚持开展长期持续性监测研究。

地埋管换热场地温度羽迁移分析

地热能作为一种可再生的清洁能源,对推进我国能源发展、实现国家“双碳”目标将发挥重要作用.目前浅层地热能的开发利用主要通过热泵技术来实现,为分析不同方向渗流的地下水对地埋管换热场地地温场的影响,分别采用现场监测和数值模拟进行分析.结果表明:(1)制冷和供暖期内,平行于地下水流向岩土体温度影响5 m左右,其中2.5 m范围内变化明显;垂直于地下水流向温度影响3 m左右,其中2 m以内变化明显.(2)地源热泵运行20年后平行于地下水流向温度羽迁移距离为84.37~142.15 m,含水层颗粒愈粗地下水渗流愈强,迁移距离愈远;垂直于地下水流向温度羽迁移距离为38.14~39.77 m,由上至下基本呈递减趋势;(3)预测20年后地温升高0.55~2℃.说明地源热泵运行时,在地下水渗流驱动下温度羽向下游和四周迁移,减缓或阻止热量累积,换热场地未形成明显的热堆积,预测其运行对温度场影响较小.

基于水热耦合的眉县城区地下水抽采回灌地热开发模型

以眉县滨河新区地热井工程为研究对象,结合“一抽一灌”开采方案建立地下水抽采回灌地热开发模型。基于水热多物理场耦合理论利用COMSOL多物理场数值软件进行抽采井水温和地下热储层温度模拟研究。研究结果表明:在抽采前20 d内,抽采井水温下降较快,超过20 d后,抽采井温度下降速率变缓,结合实际工况4个月的取热期,抽采回灌4个月后,抽采井水温温度基本稳定在60度;含水层4个月内的平均温度变化不大,从初始的61.5℃降至大约为60.5℃,并且模拟结果显示40 d左右温度场基本稳定。