Study of geothermal water intrusion due to groundwater exploitation in the Puebla Valley aquifer system, Mexico

Significant intrusion of geothermal water into fresh groundwater takes place in the Puebla Valley aquifer system, Mexico. The decline in the potentiometric surface due to the overexploitation of the groundwater induces this intrusion. This hydrological system comprises three aquifers located in Plio-Quaternary volcanic sediments and Mesozoic calcareous rocks. The hydraulic balance of the aquifer shows that the annual output exceeds the natural inputs by 12 million m³. Between 1973 and 2002, a drop in the potentiometric surface, with an 80 m cone of depression, was identified in a 5-km-wide area located southwest of the city of Puebla. Chemical analyses performed on water samples since 1990 have shown an increase in total dissolved solids (TDS) of more than 500 mg/L, coinciding with the region showing a cone of depression in the potentiometric surface. A three-dimensional flow and transport model, based on the hydrogeological and geophysical studies, was computed by using the MODFLOW and MT3D software. This model reproduces the evolution of the aquifer system during the last 30 years and predicts for 2010 an additional drawdown in the potentiometric surface of 15 m, and an increase in the geothermal water intrusion.     

Research on the fault controlling mechanism of geothermal water in Zhangzhou Basin

Fault has an important influence on the storage and movement of geothermal water. The Zhangzhou Basin is wholly located in a granodiorite rock mass. Due to the low permeability of granodiorite, faulted structure has an evident control action on the hydrothermal activity of geothermal fields. Hot springs in Zhangzhou Basin crack along Pingtan-Dongshan Fault to the northeastern direction and emerge along Fu’an-Nanjing Fault. Through measurement of the temperature of several hot springs in the Basin, we found the temperature along the northwestern direction of Zhangzhou-Tianbao Fault is high and the temperature gap between the two sides of Yangxi-Yuanshan Fault is huge; the estimation of geothermal reservoir temperature of geothermal water through quartz geothermometer indicates that the geothermal reservoir temperature of the northern area of Nanjing-Xiamen Fault is obviously higher than that of southern area. Such result indicates that Fault obviously obstructs underground heat source. Under the condition that the average geothermal gradient of the Zhangzhou Basin is set, the circulation depth of the geothermal water of the Zhangzhou Basin measured by geothermal reservoir temperature is 3 550-5 200 m and the circulation depth of the geothermal water of the north of Nanjing-Xiamen Fault is deeper than that of the South.     

The geothermal formation mechanism in the Gonghe Basin: Discussion and analysis from the geological background

The Gonghe Basin, a Cenozoic down-warped basin, is located in the northeastern part of the Qinghai-Xizang (Tibetan) Plateau, and spread over important nodes of the transfer of multiple blocks in the central orogenic belt in the NWW direction. It is also called “Qin Kun Fork” and “Gonghe Gap”. The basin has a high heat flow value and obvious thermal anomaly. The geothermal resources are mainly hot dry rock and underground hot water. In recent years, the mechanism of geothermal formation within the basin has been controversial. On the basis of understanding the knowledge of predecessors, this paper proposes the geothermal formation mechanism of the “heat source–heat transfer–heat reservoir and caprock–thermal system” of the Gonghe Basin from the perspective of a geological background through data integration-integrated research-expert, discussion-graph, compilation-field verification and other processes: (1) Heat source: geophysical exploration and radioisotope calculations show that the heat source of heat in the basin has both the contribution of mantle and the participation of the earth’s crust, but mainly the contribution of the deep mantle. (2) Heat transfer: The petrological properties of the basin and the exposed structure position of the surface hot springs show that one transfer mode is the material of the mantle source upwells and invades from the bottom, directly injecting heat; the other is that the deep fault conducts the deep heat of the basin to the middle and lower parts of the earth’s crust, then the secondary fracture transfers the heat to the shallow part. (3) Heat reservoir and caprock: First, the convective strip-shaped heat reservoir exposed by the hot springs on the peripheral fault zone of the basin; second, the underlying hot dry rock layered heat reservoir and the upper new generation heat reservoir and caprock in the basin revealed by drilling data. (4) Thermal system: Based on the characteristics of the “heat source-heat transfer-heat reservoir and caprock”, it is preliminarily believed that the Gonghe Basin belongs to the non-magmatic heat source hydrothermal geothermal system (type II2₁) and the dry heat geothermal system (type II2₂). Its favorable structural position and special geological evolutionary history have given birth to a unique environment for the formation of the geothermal system. There may be a cumulative effect of heat accumulation in the eastern part of the basin, which is expected to become a favorable exploration area for hot dry rocks.     

1980～1994年台湾海峡两岸的地热涡与降水季度预报初探

利用１９８０～１９９４年大陆３．２ｍ深度和台湾３．０ｍ深度的地温资料,分析了１５ａ来的逐季地气图,统计了台湾海峡两岸的地热涡活动,发现平均每季有１个地热涡活动,其水平尺度比大陆内部的地热涡要小,生命史也要短,进入台湾地区的地热涡绝大多数是从西方和北方进入,其移动速度比大陆内部的要快得多。９０％以上的地热涡在同期有多雨区与其对应,热涡中心与多雨中心相距在１００ｋｍ以内者占６８％。最后给出了一个季度降水的定性预测方案,其步骤为：预报地热涡的中心位置、强度和水平尺度;推算降水正距平区的水平尺度、中心位置和强度;根据本区发生的地震等情况进行预报订正。     

Occurrence and evolution of the Xiaotangshan hot spring in Beijing, China

Thermal groundwater occurs in bedrock aquifers consisting of the dolomite of the Wumishan Group of the Jixianin System and the Cambrian carbonate in the Xiaotangshan geothermal field near the northern margin of the North China Plain, China. The hot water in the geothermal field of basin-type discharges partly in the form of the Xiaotangshan hot spring under natural conditions. The hot water has TDS of less than 600 mg/L and is of Na·Ca-HCO₃ type. The geothermal water receives recharge from precipitation in the mountain area with elevation of about 500 m above sea level to the north of the spring. Thermal groundwater flows slowly south and southeast through a deep circulation with a residence time of 224 years estimated with the Ra–Rn method. The Xiaotangshan hot spring dried up in the middle of the 1980s owing to the increasing withdrawal of the hot water in the geothermal field in the past decades. The water level of the geothermal system still falls continually at an annual average rate of about 2 m, although water temperature changes very little, indicating that the recharge of such a geothermal system of basin-type is limited. Over-exploitation has a dramatic impact on the geothermal system, and reduction in exploitation and reinjection are required for the sustainable usage of the hot water.     

Geothopica and the interactive analysis and visualization of the updated Italian National Geothermal Database

The Italian National Geothermal Database (BDNG), is the largest collection of Italian Geothermal data and was set up in the 1980s. It has since been updated both in terms of content and management tools: information on deep wells and thermal springs (with temperature > 30 °C) are currently organized and stored in a PostgreSQL relational database management system, which guarantees high performance, data security and easy access through different client applications. The BDNG is the core of the Geothopica web site, whose webGIS tool allows different types of user to access geothermal data, to visualize multiple types of datasets, and to perform integrated analyses. The webGIS tool has been recently improved by two specially designed, programmed and implemented visualization tools to display data on well lithology and underground temperatures.This paper describes the contents of the database and its software and data update, as well as the webGIS tool including the new tools for data lithology and temperature visualization. The geoinformation organized in the database and accessible through Geothopica is of use not only for geothermal purposes, but also for any kind of georesource and CO₂ storage project requiring the organization of, and access to, deep underground data. Geothopica also supports project developers, researchers, and decision makers in the assessment, management and sustainable deployment of georesources.     

层次分析法创建地热水前景评价模型的研究

在地热能源不断得到关注和利用的当今社会,对其科学合理地开发利用显得尤为重要。文章采用层次分析法和多目标决策的线性加权相结合的方法建立了地热水开发利用前景评价模型,避免了以往单纯从定性角度分析地热水开发利用前景的人为主观性及片面性,保证了评价结果的客观准确,经实例验证,是一种行之有效的评价方法。作者选取地热地质条件、经济发展水平、开发利用现状作为层次分析法的中间层要素,进而将其进一步分解为不同的组成因素,运用层次分析法计算出各项指标的权重,结合多目标决策的线性加权方法建立综合评价评分的数学模型,最后根据地热田的实际情况,综合评价,确定评价结果。     

山东省聊城东部地热田水质特征及开发利用研究

山东聊城东部地热田位于阳谷凸起的北部区内,区内常被开发利用的奥陶纪马家沟组热储层的地热流体主要为地热水,其矿化度和温度较高,水量较大,属氯化物·硫酸盐一钠·钙型和中性极硬型盐水;其锶、氟的含量达到了命名矿水浓度;偏硼酸的含量达到了有医疗价值浓度,有时会达到矿水浓度;偏硅酸的含量达到了矿水浓度;对金属具有强腐蚀性,对普通水泥具有结晶性侵蚀,对各类水泥无分解性侵蚀,并含有铁、锂、锰等多种对人体有益的微量元素。可以在地热供暖、洗浴、医疗保健、种植业、养殖业、工业等行业进行广泛地开发利用。     

Geothermal resources formation conditions and preferred target areas in a certain county of Western Sichuan,China

The geothermal resource is a form of "green" and renewable energy with huge development potential in terms of both environmental protection and economy. It was concluded that the exposed hot springs were mostly produced when fluids derived from atmospheric precipitation were heated deep and recurrently under the ground, developed banded geothermal reservoir in the pores of fault damage zones, fissure zones, hornification zones and dikes, and then moved upward with analyzing the geological and hydrogeological data as well as hydrochemical types of the naturally exposed hot springs in the studied region so as to ascertain the accumulation conditions of geothermal resources in a particular county in Western Sichuan and opt for suitable target areas for exploring geothermal resources. Four areas where geothermal resources are potentially located were proposed with analysis of their formation conditions based on this notion, and the "epsilon-shaped" structure in Zhimulin, the "epsilon-shaped" structure in Jiaochang, the vortex structure in Rewugou and the arcuate structure in Shidaguan were analyzed in this paper offering a reference for developing and exploiting the geothermal resources in the region as well as studying the development patterns of other hot springs in this region.     

利用钻孔温度梯度重建过去气候变化进展

地球表面的温度信号向地下传播并影响地下温度剖面,这种温度剖面可从钻孔中测量,通过分析可重建过去表面温度变化.虽然认识到表面温度变化对地下温度和热流的影响已有很长时间,但仅在20世纪80年代以后钻孔温度剖面才被广泛应用于气候变化研究.钻孔气候方法与其他重建过去气候的近似方法不同,因为它是基于温度剖面测量与过去气候,即地表温度(GST)、重构参数的直接物理联系之上的.钻孔温度气候研究方法已被证实可以重建过去地表温度趋势,并且最终可结合表面气温序列估计其预观测平均值(POMs).钻孔温度剖面并不是地表温度的代用指标,而是地球大陆表面能量平衡的直接测量.这种地下的信号通过热扩散衰减非常快,因而对从地下温度测量数据中提取过去气候变化信息的方法施加了一个物理限制.描述由钻孔中测量的温度—深度剖面来重建GST历史的基本特征及问题.