1. 引言
1. Introduction
在全球能源革命和能源产业优化升级的背景下,地热能作为不受天气变化影响的可再生能源,因其储量丰富、安全高效和运维成本低等优点,正成为能源消费转型的重点【1】。2022年6月,国家发展改革委公布的《“十四五”可再生能源发展规划》中强调了积极推进地热能的大规模开发,并持续优化地热能开发利用的政策框架,为地热能产业的稳定增长和高质量进步提供了坚实的政策支撑。自2015年起,我国地热能直接利用规模稳居世界第一,取得了良好的经济、社会与环境效益。据研究表明,我国地热资源呈“东高、中低、西南高、西北低”的总体分布格局。受板块边缘高温地热带影响,其中藏南、滇西、川西及台湾等地是我国高温地热资源开发利用的主要靶区;而中低温地热资源分布较为广泛,主要集中于东部华北盆地、苏北盆地、松辽盆地及西部鄂尔多斯盆地等沉积盆地处【23】。迄今为止,我国已确认的地热资源储量占全球地热资源总量的8%,约等同于4000亿吨标准煤。【4】。其中,受隆起山地及沉积盆地等地质构造特征影响,安徽省内地热资源丰富【5】,预计到2025年地热能建筑供暖制冷应用面积将达到2000万平方米。因此,我国地热能开发应用潜力巨大,有望成为我国能源结构中的重要组成部分,为实现碳中和目标做出积极贡献。
In the context of the global energy revolution and the optimization and upgrading of the energy industry, geothermal energy, as a renewable energy that is not affected by weather changes, is becoming the focus of energy consumption transformation due to its abundant reserves, safety and efficiency, and low operation and maintenance costs [1]. In June 2022, the National Development and Reform Commission (NDRC) announced the 14th Five-Year Plan for Renewable Energy Development, which emphasizes actively promoting the large-scale development of geothermal energy and continuously optimizing the policy framework for the development and utilization of geothermal energy. It provides a solid policy support for the stable growth and high-quality progress of the geothermal energy industry. Since 2015, China's direct utilization of geothermal energy has ranked first in the world, and has achieved good economic, social and environmental benefits. According to the research, the geothermal resources in China show an overall distribution pattern of "high in the east, middle and low, high in the southwest and low in the northwest". Affected by the high-temperature geotropical area at the plate margin, southern Tibet, western Yunnan, western Sichuan and Taiwan are the main target areas for the development and utilization of high-temperature geothermal resources in China. However, the medium and low temperature geothermal resources are widely distributed, mainly concentrated in the sedimentary basins such as the North China Basin, the North Jiangsu Basin, the Songliao Basin, and the Ordos Basin in the west [23]. So far, China's confirmed geothermal resource reserves account for 8% of the world's total geothermal resources, which is equivalent to about 400 billion tons of standard coal. 【4】。 Among them, due to the influence of geological structural characteristics such as uplifted mountains and sedimentary basins, Anhui Province is rich in thermal resources [5], and it is estimated that by 2025, the application area of geothermal energy building heating and cooling will reach 20 million square meters. Therefore, China's geothermal energy development and application potential is huge, and it is expected to become an important part of China's energy structure and make positive contributions to the realization of carbon neutrality goals.
据统计预测,在接下来的10到15年内,我国预计有一半的铁矿资源、三分之一的有色金属矿资源以及超过半数的煤炭资源将在千米深的地下进行开采。随着开采深度的增加,矿井高温热害问题日益严峻,其与高地应力、高岩溶水压一同构成了深部开采的典型环境特征。近期,部分学者针对矿山地热资源开发利用提出了若干新颖观点。张发旺【6】等通过文献综述法总结了中国煤矿地热资源分布特征,认为利用矿山地热资源可为碳减排目标作出积极贡献。Linqi Huang等【7】针对深部开采提出了一个结合CRITIC方法和不确定性测量理论的新型热害评估框架(CRITICUM),为确保现场安全和促进地热能的可持续利用提供了有价值的参考。张吉雄【8】等提出通过相变蓄热功能充填材料置换煤炭资源,构造煤系热储开发系统,实现矿山地热能的高效开发。Austin Anderson【9】等系统讨论了地热技术的发展趋势以及利用废弃矿井进行地下能源存储和地热应用的潜力,指出矿山地热技术在未来具有重要地位。
According to statistics, it is predicted that in the next 10 to 15 years, half of China's iron ore resources, one-third of non-ferrous metal ore resources and more than half of coal resources will be mined underground at a depth of kilometers. With the increase of mining depth, the problem of high temperature and heat damage in mines is becoming more and more severe, which together with high geostress and high karst water pressure constitute the typical environmental characteristics of deep mining. Recently, some scholars have put forward some novel views on the development and utilization of geothermal resources in mines. Zhang Fawang et al. [6] summarized the distribution characteristics of geothermal resources in China's coal mines through a literature review method, and concluded that the use of geothermal resources in mines can make a positive contribution to the goal of carbon emission reduction. Linqi Huang et al. [7] proposed a novel thermal hazard assessment framework (CRITICUM) that combines the CRITIC method and the uncertainty measurement theory for deep mining ), which provides a valuable reference for ensuring site safety and promoting the sustainable use of geothermal energy. Zhang Jixiong et al. [8] proposed to replace coal resources with phase change heat storage function filling materials, and construct a coal measure heat storage development system to realize the efficient development of mine geothermal energy. Austin Anderson et al. [9] discussed the development trend of geothermal technology and the potential of using abandoned mine shafts for underground energy storage and geothermal applications, pointing out that mine geothermal technology has an important place in the future.
此外,在水热型矿山地热系统聚热模式研究方面,王贵玲【10】等提出了“同源共生-壳幔生热-构造聚热”的中国地热资源的成因理论,并基于系统论观点,详细分析了典型水热系统的运移条件、热源机制及成因模式,为区域地热资源勘查开发提供了理论依据。Yanhe Li等【11】揭示了平顶山煤田地热系统的二元构造聚热模式,指出该地区岩石热导率和区域构造的空间配置共同决定了其高地温状态。李金玺【12】等基于四川盆地及其周缘地质构造,提出了褶皱型、单斜型和褶皱-断裂复合型三种水热型地热资源的构造成因模式,认为构造运动是形成现今地温分布的主要原因。H.Barcelona【13】提出了Bañitos-Gollete地热系统的概念模型,认为研究区内N-S走向的断层系统对流体循环路径有显著控制作用,并为该地区地热研究指明方向。由此可见,矿山地热资源的开发利用已成为地热领域的重要课题,其不仅是解决深部开采热害问题的重要途径,也是实现矿山可持续发展的战略选择。
In addition, in the study of the heat accumulation mode of geothermal systems in hydrothermal mines, Wang Guiling et al. [10] proposed the genesis theory of "homologous symbiosis-crust-mantle heat generation-tectonic heat accumulation" of geothermal resources in China, and analyzed in detail the migration conditions, heat source mechanism and genesis mode of typical hydrothermal systems based on the perspective of system theory, which provides a theoretical basis for the exploration and development of regional geothermal resources. Yanhe Li et al. [11] revealed the binary tectonic heat accumulation model of the geothermal system in the Pingdingshan coalfield, and pointed out that the thermal conductivity of the rocks and the spatial configuration of the regional structure in this area jointly determine the highlandTemperature status. Based on the geological structure of the Sichuan Basin and its surrounding areas, Li Jinxi et al. [12] proposed three tectonic models of hydrothermal geothermal resources: fold type, monoclinic type and fold-fault composite type. It is believed that tectonic movements are the main reason for the formation of the current geothermal distribution. H.Barcelona [1, 3] proposed a conceptual model of the Bañitos-Gollette geothermal system, arguing that in the study areaThe N-S trending fault system has a significant control effect on the fluid circulation path and points out the direction for geothermal research in this area. It can be seen that the development and utilization of geothermal resources in mines has become an important topic in the field of geothermal energy, which is not only an important way to solve the problem of heat damage in deep mining, but also a strategic choice to achieve sustainable development of mines.
本次研究采用试验与理论分析相结合的手段,基于淮北煤田信湖煤矿地热地质背景条件,分析该区域地热水的化学组成特征及其指示意义,揭示热储温度和水循环深度。同时,查明矿区地温梯度分布规律,确定区域构造对深部矿山岩溶地热系统的控制作用,并提出信湖煤矿地热系统富水聚热模式。旨在推动地热能与煤炭生产的协同发展,优化矿山地热资源的综合利用,改善矿井作业环境,同时为碳减排及我国能源结构转型贡献力量。
Based on the geothermal geological background conditions of Xinhu Coal Mine in Huaibei Coalfield, this study analyzed the chemical composition characteristics and indicative significance of geothermal water in the Huaibei Coalfield, and revealed the heat storage temperature and water circulation depth. At the same time, the distribution law of geothermal gradient in the mining area was determined, the control effect of regional structure on the karst geothermal system of deep mines was determined, and the water-rich heat accumulation model of the geothermal system of Xinhu coal mine was proposed. It aims to promote the coordinated development of geothermal energy and coal production, optimize the comprehensive utilization of geothermal resources in mines, improve the operating environment of mines, and contribute to carbon emission reduction and the transformation of China's energy structure.
2. 区域地质概况
2. Regional geology
2.1 构造特征
2.1 Structural features
信湖煤矿坐落于淮北煤田涡阳矿区中部,该煤田是华北板块东南缘,豫淮坳陷东部的中心地带。东以郯庐断裂为界与扬子板块相接,西以夏邑-阜阳断裂为界与河淮沉降带为邻。煤田构造的形成、发展与板内构造和板缘构造的演化密切相关。区内构造受东西向构造、北东向构造、徐宿弧形构造所控制,东西向和北东向构造为主要格局。主要表现为北东向构造改造早期的东西向构造。由于多期构造运动叠加的结果,区内东西向大断裂和北北东向大断裂纵横交错,形成了许多近网状的断块构造(图1)。
Xinhu Coal Mine is located in the middle of the Wuyang Mining Area of the Huaibei Coalfield, which is the southeastern margin of the North China Plate and the center of the eastern part of the Henan-Huai Depression. It is bounded by the Tanlu fault in the east and the Yangtze plate, and is adjacent to the Hehuai subsidence zone by the Xiayi-Fuyang fault in the west. The formation and development of coalfield structure are closely related to the evolution of intraplate structure and plate edge structure. The structure in the area is controlled by the east-west trending structure, the north-east trending structure and the Xusu arc structure, and the east-west and north-east trending structures are the main patterns. It is mainly manifested in the north-east-trending tectonic transformation of the early east-west tectonic structure. As a result of the superposition of multi-stage tectonic movements, the east-west and north-north-east faults criss-cross the area, forming many near-network fault block structures (Fig. 1).
图1 淮北煤田地质构造纲要图
Fig.1 Outline map of the geological structure of the Huaibei coalfield
信湖煤矿矿井为全隐蔽区,据钻探揭露,其地层层序与淮北煤田各勘查区相同,同属华北型地层范畴。在地层层序中,淮北煤田除晚奥陶世—下石炭世和三叠纪地层缺失外,其余均发育比较齐全,各地岩性和厚度虽存在一些差异,但均可对比。具体地层岩性如图2所示,其中石炭系、二叠系为含煤地层,从上至下主要由上石盒子组、下石盒子组和山西组组成。石炭系含薄煤4~5层,宿北断裂以北局部有可采煤层,宿北断裂以南无可采煤层,二叠系含煤15~30余层,可采5~10层,主要岩性为泥岩、砂岩和煤。
According to drilling, the stratigraphic sequence of Xinhu Coal Mine is the same as that of the exploration areas of Huaibei Coalfield, and it belongs to the North China type stratigraphy. In the stratigraphic sequence, except for the absence of Late Ordovician-Lower Carboniferous and Triassic strata, the Huaibei coalfield is relatively well developed, and although there are some differences in lithology and thickness, they can be compared. The specific stratigraphic lithology is shown in Figure 2, in which the Carboniferous and Permian are coal-bearing strata, which are mainly composed of the Upper Shihezi Formation, the Lower Shihezi Formation and the Shanxi Formation from top to bottom. The Carboniferous contains 4~5 layers of thin coal, there are local mineable coal seams in the north of the Subei fault, there are no minable coal seams in the south of the Subei fault, and there are more than 15~30 layers of Permian coal, which can be mined 5~10layers, the main lithologies are mudstone, sandstone and coal.
图2 淮北煤田地层综合柱状图
Fig.2 Comprehensive histogram of Huaibei coalfield stratigraph
2.2 水文地质条件
2.2 Hydrogeological conditions
信湖煤矿作为淮北煤田水文地质单元的重要组成部分,其水文地质特征受到区域构造格局的显著影响。如图1所示,淮北煤田东有固镇~长丰断层,南有板桥断层与淮南煤田相望,西有夏邑~阜阳断层及丰涡断层与太康隆起和周口坳陷为邻。周围大的断裂构造控制了该区地下水的补给、径流、排泄条件,使其基本上形成为一个封闭~半封闭的网格状水文地质单元。根据区域地层岩性的含水条件、含水赋存空间分布,可划分为新生界松散层孔隙含水层(组)、二叠系主采煤层砂岩裂隙含水层(段)和太原组及奥陶系石灰岩岩溶裂隙含水层(段)。淮北煤田各生产矿正常涌水量为100~700m3/h,矿坑直接充水水源为煤层顶底板砂岩裂隙含水层,具有补给量不足,以静储量为主的特征。出水点水量大小与构造裂隙发育程度和补给水源有密切关系,只要没有富水含水层补给,一般水量呈衰减趋势。
As an important part of the hydrogeological unit of Huaibei coalfield, the hydrogeological characteristics of Xinhu Coal Mine are significantly affected by the regional tectonic pattern. As shown in Figure 1, the Huaibei coalfield is bordered by the Guzhen~Changfeng fault in the east, the Banqiao fault in the south and the Huainan coalfield, and the Xiayi~Fuyang fault and the Fengwu fault in the west, which are adjacent to the Taikang uplift and Zhoukou depression. The surrounding large fault structure controls the recharge, runoff and discharge conditions of groundwater in the area, making it basically form a closed ~ semi-closed grid-like hydrogeological unit. According to the water aquifer conditions and spatial distribution of water occurrence of regional stratigraphic lithology, it can be divided into Cenozoic loose layer pore aquifer (group), Permian main coal mining seam sandstone fissure aquifer (section) and Taiyuan Formation and Ordovician limestone karst fissure aquifer (section). The normal water inflow of each production mine in Huaibei coalfield is 100~700m3/h, and the direct water source of the pit is the sandstone fissure aquifer of the top and bottom plate of the coal seam, which has the characteristics of insufficient recharge and static reserves. The amount of water at the outlet point is closely related to the development degree of tectonic fractures and the recharge source, and as long as there is no recharge from the water-rich aquifer, the general water volume shows a decreasing trend.
3. Sample and method
本研究共采集信湖煤矿12份地热水样品,分别来自G1、G2、G3井基岩混合层,G4、G7、G8、G11、G12井奥陶系灰岩层,G5、G6、G10井煤层顶底板砂岩层,以及G9井F1断层处,进行水质全分析检验。样品采集后被保存于预先经过酸洗和去离子水冲洗的瓶子内,以避免外部污染。并在每个采样点均收集了充足的样本量,以便进行后续pH、TDS、主要和微量元素的测定。在现场,首先利用经过校准的便携式仪器(HQ40D)完成pH值的测定。主要阳离子和微量元素的分析样本通过使用纯硝酸酸化处理,使其pH值低于2。其中阳离子如Na+、K+、Ca2+和Mg2+等的浓度测定是通过ICP-OES(ThermoFisher IRIS Intrepid II XSP)进行的,仪器准确度在1%以内。微量元素的分析则通过ICP-MS(Agilent 7800)完成。对于阴离子的定量分析,我们采用了离子色谱法(ICS-1000)来测定F−、Cl−、NO3−和SO42−等的含量,精度在5%以内。此外,SiO2的含量测定是通过分光光度法实现的。
A total of 12 geothermal water samples were collected from the bedrock mixed layers of well G1, G2 and G3 in this study. Ordovician limestone formations in well G4, G7, G8, G11 and G12, the sandstone layers of the coal seam roof and floor in well G5, G6 and G10, and F1 in well G9At the fault, the water quality is fully analyzed and tested. After collection, samples are stored in bottles that have been pre-pickled and rinsed with deionized water to avoid external contamination. Sufficient sample volumes were collected at each sampling point for subsequent determination of pH, TDS, major and trace elements. In the field, the pH is first determined using a calibrated portable instrument (HQ40D). Samples for the analysis of major cations and trace elements were acidified with pure nitric acid to bring their pH below 2. Among them, cations such as Na+, K+, Ca2+and Mg2+, etc., concentration determination is performed by ICP-OES (ThermoFisher IRIS Intrepid II XSP).The accuracy of the instrument is within 1%. Trace element analysis is performed by ICP-MS (Agilent 7800).For the quantitative analysis of anions, we used ion chromatography (ICS-1000) to determine F−, Cl−, NO3− and SO4 2−and so on, and the precision is within 5%. In addition, the determination of SiO2 content is achieved by spectrophotometry.
4. 地热水地球化学特征
4. Geochemical characterization of geothermal water
4.1 水化学分析结果
41 Results of water chemistry analysis
通过piper三线图(图3)用以描述地下水中的阴阳离子含量,可以直观地看出各水样点中的占优离子,从而对水化学相进行分类。本次研究中,我们收集来自信湖煤矿12个矿井的水文地球化学数据(表1),进行水化学特征分析。结果表明,在阳离子中,Na++K+占阳离子总量的70%以上,Mg2+占比不足10%,Ca2+占比不足20%,说明信湖煤矿地热水中阳离子以Na++K+为主。在阴离子中,水样点多位于右下方,主要有Cl-、SO42-、HCO3-等,其中以Cl-为甚,占阴离子总量的50%~80%,表明该区域地热水主要以Na-K-Cl-SO4型为主。此外,在水文地质学中,常利用Gibbs图(图4)分析地下水化学成分的来源和控制因素。Gibbs模型将地下水化学组分的控制因素分为降雨控制型、岩石风化型和蒸发浓缩作用型三类。图示绝大部分水样点具有高TDS,高Cl-/Cl-+HCO3-值的特征,处于蒸发沉淀区。这表明水体中的化学成分主要是由于水分蒸发导致的盐分浓缩控制的。
The Piper three-line diagram (Fig. 3) is used to describe the anions and cations in groundwater, and the dominant ions in each water sample can be visually seen, so as to classify the water chemical phases. In this study, we collected hydrogeochemical data from 12 shafts in Xinhu Coal Mine (Table 1) for hydrochemical characterization. The results showed that Na++K+ accounted for more than 70% of the total cations, and Mg2+ accounted for more than 70% of the total cations The proportion was less than 10%, and the proportion of Ca2+ was less than 20%, indicating that the cation in the geothermal water of Xinhu Coal Mine was Na++K+-based. In the anions, the water samples are mostly located in the lower right, mainly Cl-, SO42-, and HCO3-, of which Cl- is the most important, accounting for the total anion50%~80%, indicating that the geothermal water in this area is mainly Na-K-Cl-SO4 type. In addition, in hydrogeology, Gibbs diagrams (Figure 4) are often used to analyze the sources and controlling factors of groundwater chemical composition. The Gibbs model divides the controlling factors of groundwater chemical composition into three types: rainfall control type, rock weathering type and evaporation concentration type. The figure shows that most of the water samples have high TDS and high Cl-/Cl-+HCO3- Characteristics of the value, which is in the zone of evaporation precipitation. This indicates that the chemical composition in the water body is mainly controlled by salt concentration due to water evaporation.
图3 地热水Piper三线图
Figure 3: Three-line diagram of geothermal water Piper