【作者】 肖琼；

【导师】 袁道先；

【作者基本信息】 西南大学 ， 自然地理学， 2012， 博士

【摘要】 在石油、煤炭、天然气等传统能源面临枯竭的今天,新能源和可再生能源的开发成为世界经济可持续发展的前提。浅层地热能作为一种可再生的新型环保能源和特殊矿产资源,其开发利用对构建资源节约型和环境友好型社会、保障国家能源安全、改善我国现有能源结构、促进国家节能减排战略目标的实现具有非常重要的意义。重庆是中国西部唯一的直辖市,其浅层地热资源丰富,主要集中分布在重庆都市圈内的川东平行岭谷地区,其浅层地热资源的开发主要以温泉休闲旅游为主。2011年,重庆市被评为“中国温泉之都”,2012年,重庆市欲打造成为“世界温泉之都”。因此,对重庆地区的浅层地热水的来源、水—岩作用过程以及水中各离子的来源和转换等基础性工作的研究显得尤为重要。本研究对川东平行岭谷地区的地下热水(包括温泉出露和人工钻井)进行野外监测、取样和室内分析,并通过对重庆三叠系碳酸盐岩热储的补给区域、径流过程、物质来源的研究建立重庆三叠系碳酸盐岩热储补、径、排概念模型。重庆主城区浅层地热水主要为重庆三叠系碳酸盐岩热储热水,其地质特征表现为储水层为下三叠统嘉陵江组的碳酸盐岩。上覆盖层为上三叠统须家河组的致密性砂页岩,下伏底层为下三叠统飞仙关组的碎屑岩夹碳酸盐岩。合理的储水储热构造使得重庆川东平行岭谷地区形成了“山山有资源、峡峡有温泉”的热水库。重庆三叠系碳酸盐岩储热系统内所有的地下热水水化学性质相近,其基本特征为pH值呈中性,电导率较高,水温30℃～50℃之间,属浅层中低温地下热水,水化学类型为S04-Ca(Mg)型,是典型的碳酸盐岩热储地下热水。其主要阳离子为Ca2+和Mg2+,主要阴离子为S042-和HC03-,除青木关温泉外,S042-和Ca2+、Mg2+随时空变化较小。热水中的方解石和白云石都处于饱和与不饱和的临界状态,没有明显钙华沉积的现象；Na-K-Mg-Ca图解显示地下热水没有达到水岩平衡状态且各个季节地下热水的物质来源基本—致。重庆三叠系碳酸盐岩热储热水的δD值分布在-63.08%o--48.62%o之间,δ18O的值在-9.5%o--6.47%o之间,δD(‰)和δ18O(‰)值的线性关系为δD=(7.666±0.283)δ180+(6.88±2.35)δD,与全球大气降水线接近,表明其补给来源为大气降水。地下热水δD值的d-excess值都落在d-excess=0‰和d-excess=20‰之间,且主要集中在d-excess=10‰附近,表明在水—岩作用中,没有发生明显的δ180漂移。根据氢氧同位素的高程效应,计算得出重庆三叠系碳酸盐岩热储热水的补给区主要是位于海拔460m-1613m的地区。结合长江、嘉陵江对川东平行岭谷背斜内地下水循环的控制,可以认为地下热水的补给来源为川东平行岭谷北端的岩溶出露区域和川东平行岭谷内岩溶槽谷区,主要是北端的岩溶出露区。使用高分辨率的自动检测仪器CDTP在线监测北温泉2009-2010年降雨量、北温泉水流量、pH值、水温以及电导率等并分析统计,发现自然出露点地下热水的流量、水温、电导率、以及pH值总体上稳定,但是在一年中,温泉水的流量与当地降雨量存在一定的滞后关系,雨季温泉水流量小,旱季温泉水流量偏大。此外,2008年5.12地震期间对北温泉的水化学特征的监测表明极端地质事件导致北温泉砂岩盖层和含水层裂隙增多、增大,以致盖层裂隙与含水层裂隙贯通,地表或上覆盖层低温水汇入含水层,引起北温泉泉群水温、水量以及水化学特征的变化。重庆三叠系碳酸盐岩热储地下热水高SO42-而低HCO3-是其最显著的特征,也是研究其水—岩作用的关键。HC03-与Ca2+、Mg2+、Sr2+成负相关关系,HCO3-与SO42-也存在很强的负相关关系,表明Ca2+、Mg2+、Sr2+以及SO42-的存在对HCO3-有一定的抑制作用。通过HC03-的δ13C和He同位素分析发现重庆三叠系碳酸盐岩热储热水存在幔源来源。其中地下热水中HC03-的δ13C值为-9.73%o-3.12‰,表明参与水—岩反应的C02可能既有生物成因,又可能有幔源成因。地下热水的(3He/4He)的比值R与空气的标准气样3He/4He的比值Ra相比,均大于1,佐证了地下热水有幔源的说法。根据同位素质量平衡原理计算得出参与水—岩反应的CO2中,25.2%-68.73%来自于土壤,幔源的占31.27%-74.8%。重庆碳酸盐岩热储S042-的含量异常高,且其SO42-的δ34S值在29.70‰-34.32‰之间,异常偏正,体现了下三叠统嘉陵江组二段石膏的δ34S特征。异常高的SO42-源于研究区碳酸盐岩中石膏的溶解,而异常偏正的δ34S值源于四川盆地在早三叠世嘉二期时相对封闭的盐湖环境,强烈的蒸发作用有利于蒸发岩类的形成,水体中的硫酸盐与有机质接触,厌氧微生物的脱硫作用将硫酸盐还原分解出H2S和C02,即细菌从硫酸盐离子中分解出氧,释放出具有比硫酸盐更富集32S的H2S,有利于34s在硫酸盐岩中的富集,导致硫酸盐岩中的34S的增高。综合地下热水中87Sr/86Sr和δ13C以及SO42-的δ34S值,其中8042-的δ34S较高,体现了三疊系嘉陵江组二段石膏的特征；87Sr/86Sr较低,体现了碳酸盐岩风特征；而雨季温泉水δ348值较旱季偏轻,δ13C值雨季较早季偏重,主要原因是一些地表径流和砂岩裂隙水通过盖层中的裂隙与温泉水混合,导致温泉水中同位素值出现季节性的差异。根据以上水化学、同位素等监测数据,结合研究区地质背景分析,可以归纳重庆三叠系碳酸盐岩热储的补给区域、径流过程、物质来源并建立其补、径、排概念模型：在高程460m-1613m的川东平行岭谷北端的灰岩裸露区和川东平行岭谷的岩溶槽谷区,大气降水和地表径流等入渗补到一个以碳酸盐岩为储热层,砂页岩为上覆盖层、碎屑岩夹灰岩为下伏底层的碳酸盐岩储水系统。水在此储水层中经历了较长的流动途径,不断吸收周围岩体的热量,同时,少量的幔源物质沿地下的裂隙等进入储水层进行混合,发生了石膏的溶解与有C02和H20参与的碳酸盐岩的风化为主的水—岩反应。在径流过程中,地下热水在断裂带上或者是大江大河深切峡谷时受阻,向上运动,并与浅部岩溶冷水和砂岩裂隙水混合,以泉点或者人工钻井的形式排出。更多还原

【Abstract】 Nowadays, the non-renewable energy sources such as oil, coal and natural gas are being exhausted, therefore, the exploitation of new energy and renewable energy is a premise for sustainable development of world economy. The exploitation of shallow geothermal energy, a new renewable clean energy and a special mineral resources, is very important for building a Resource-conserving and Environment-friendly Society, ensuring national energy safety, adjusting the existing energy structure, and promoting the achievement of the goals of energy saving and green house gas mitigation. Chongqing City, the only municipality in southwestern China, is rich in shallow geothermal energy, which is mostly distributed in the area of eastern Sichuan parallel Ridge and Valley. Its exploitation currently is mainly for the Spa leisure tourism, so Chongqing is named as "A Spa city of China" in2011, and is expected to be "A Spa city in the world" in2012. So, it is very important to carry out the researches on the origin of the geothermal water, water-rock interaction, ions’source and migration of the shallow geothermal energy. In this study, the underground thermal water (including natural outcrops and manual drilling) in the area of eastern Sichuan parallel Ridge and Valley were measured and sampled in fields, and then analyzed in the Laboratory. And a conceptual model of recharge, streamflow and discharge of the thermal water in Carbonate Reservoir in Triassic was established through the study on the recharge regional, runoff process and matter resources of the thermal water in Carbonate Reservoir in Triassic in Chongqing.Shallow geothermal water in Chongqing City is the underground thermal water of Triassic Carbonate reservoir. Its geological features are shown that the reservoir bed is located in the carbonate rocks in Jialingjiang formation in Lower Triassic, covered by the sandstone and shale in Xujiahe formation in Upper Triassic as the cap rock, and the Clastic rocks with carbonate rocks in Feixianguan formation in Lower Triassic as the bottom rock. The best reservoir structure made the eastern Sichuan parallel Ridge and Valley a huge Heat reservoir with hot springs found in many gorges.It was found that the hydrochemical properties of most of the underground thermal waters are the similar featured by neutral pH, high Electrical Conductivity(EC) and temperature ranging among30℃to50℃, which were identified to low-medium temperature shallow geothermal water. The major cations of these thermal water are Ca2+and Mg2+and the major anions are SO42-and HCO3-, so the chemical types of theses underground thermal water are SO4-Ca (Mg) type, which is a kind of typical Triassic Carbonate Reservoir thermal water. The concentration of SO42-and Ca2+、Mg2+varies slightly by time but significantly by the space. The concentration of SO42-and Ca2+、Mg2+in two springs in Qingmuguan are lower than those in others because of the outcroping geology environment. The calcite and dolomite in the underground thermal water are under the critical state of saturated to unsaturated, and there is no obvious phenomenon of travertine deposition. Na-K-Mg-Ca diagram shows the thermal water in Carbonate Reservoir in Triassic in Chongqing haven’t reach the water-rock equilibrium, and the sources of the matters in thermal water are basically the same in each season.The value of δD about the thermal water in Carbonate Reservoir in Triassic in Chongqing is between-63.08%o and-48.62%o, while the value of δ18O varies from-9.5%o to-6.47%o. The linear relationship between δD (‰) and δ18O (‰) is δD=(7.666±0.283) δ18O+(6.88±2.35) δD, which is mostly closed to global meteoric water line, therefore, it is confirmed that the source of the thermal water in Carbonate Reservoir in Triassic in Chongqing is from meteoric water. As the difference in temperature between the thermal water and external environment is small, there is no apparent drift of the δ18O in water-rock interaction. Therefore, the value of d is about d=0‰and d=20‰, mainly concentrating in the vicinity of d=10‰.The value of δ18O about the thermal water in Carbonate Reservoir in Triassic in Chongqing is between-9.5%o and-6.47%o and the recharging area of this thermal water is at an altitude of460m～1605m. Taking into account together with the Yangzi River and Jialing River which control the underground water circulation in the anticlines in eastern Sichuan parallel Ridge and Valley, it can be realized that the recharging area of the thermal water are the karst areas on the north of the eastern Sichuan parallel Ridge and Valley and the Karst valley in eastern Sichuan parallel Ridge and Valley, but mostly is the karst area on the north.A high-resolution automatic detection instrument (CDTP) was used to monitor the pH, temperature, EC and runoff of rain gauge. A lot of data were collected. The data in2009and2010showed that the pH, temperature, EC and runoff in outcropped springs were stable, but the runoff of the spring is larger in dry season and smaller in rainy season. Research on extreme geological events is a common way to study underground thermal water. The hydrocheimcal features of the north spring (BWQ) were measured during the earthquake in Sichuan on May12,2008. The results showed that fissures in the cap rock and reservoir bed turned to be more after the earthquake and the allogenic water filtered into the reservoir bed and lead to the change of the temperature, water quantity and chemical characteristics of BWQ.The most striking feature of the thermal water in Carbonate Reservoir in Triassic in Chongqing is high concentration of SO42-and low concentration of HCO3-, and it is the key point for studying the water-rock interaction. There is a negative correlation between the concentration of HCO3-and that of Ca, HCO3-, Mg and of Sr; the concentration of HCO3-are also in strong negative correlation with SO42-. It can be realized that the concentration of Ca, Mg, Sr and SO42-in thermal water restrict the concentration of HCO3-in thermal water. The values of δ13C.DIC in the thermal water are between-9.73‰and-3.12‰, which means that the source of CO2joined in the water-rock interaction are from both biological and mantle sources. The ratio of the value of3He/4He about the thermal water and the value of3He/He about air is bigger than1, which also means that there are some matters from mantle. It was calculated that of the total CO2that were active in the water-rock interaction,25.2%～68.73%is from the soil and31.27%～74.8%from the mantle.The concentration of SO42-in thermal water in the Carbonate Reservoir in Triassic in Chongqing is very high and the value of δ34S-SO42-is very heavy which is about29.70‰～34.32‰. The reason for the high concentration of the SO42-is the solution of the gypsum in the carbonate rock in the study area. And the reason for the heavy value of δ34S-SO42-is because of the salt lake in the second period of Jialingling formation in Lower Triassic. Evaporate rocks were formed with strong evaporation, and the sulfate touched with organic matter, decomposing to H2S and CO2under the reducing action of the Anaerobic microorganisms. That is the reducing action of the bacterial made the oxygen get out of the sulfate-ion and release the H2S with more32S than sulfate. This process enriched the34S in the sulfate and made the value of δ34S-SO42-heavy.The Value of87Sr/86Sr and δ13C in thermal water in Carbonate Reservoir in Triassic in Chongqing is light and the value of δ34S is heavy. The high value of δ34S means the source of SO42-is the gypsum in the second section of Jialingjiang formation in lower Triassic. Due to the surface runoff and sandstone water filter into cracks in cap rock and mixed with thermal water, resulting in seasonal differences of the value of isotopes in underground thermal water. The value of87Sr/86Sr means the source of Sr is carbonate rock. The value of δ34S is lighter in rain season and the value of δ13C is heavier in rain season.A conceptual model of recharge, streamflow and discharge of the thermal water in Carbonate Reservoir in Triassic was established through the study on the recharge regional, runoff process and matter resources of the thermal water in Carbonate Reservoir in Triassic in Chongqing. On the area of the karst area on the north of the eastern Sichuan parallel Ridge and Valley and the karst valley in eastern Sichuan parallel Ridge and Valley that at the altitude of460m to1605m, the precipitation and surface runoff infiltrate into the a Carbonate Reservoir system with the carbonate reservoir bed, sandstone and shale cap rock, and the clastic rocks as carbonate rocks bottom. Water in this aquifer has experienced long flow paths, constantly absorbing the heat from the surrounding rock, mixing with the matters from the mantle and dissolving the gypsum, weathering the carbonate rock with CO2and H2O. During the progress of runoff, the underground thermal water is suffocated by the fault or the valley that were deep dissected by Yangzi river and Jialing River, and then upward moving, mixing with the cold karst water and sandstone water, at last discharged as natural outcropping springs and manual drilling springs.更多还原