Ammonia and boric acid in steam and water. Experimental data from geothermal wells in the phlegrean fields, Naples, Italy

In this study the variation in volatility with temperature of boric acid and ammonia is examined through experimental tests on fluids taken from Mofete 3 and Mofete 9 wells (Phlegrean Fields, Naples). Some samples of the brine and of the steam have been collected after separation of the two phases through a cyclone separator at different temperatures in the range 122–166°C. The distribution of the two species between liquid and steam agrees with known experimental data.     

The nestos delta geothermal field and its relation to the associated self potential (sp) field

Prospecting for geothermal reservoirs by geophysical methods has proved to be a challenge in recent years. In the case of Nestos geothermal field, considered to be a blind field (no surface manifestation), the geological and geophysical data were studied and intercorrelated. The geophysical results from SP, gravity, and VES data were compared with basement morphology and tectonics, as well as with the high temperatures measured in the area of main geothermal interest. As a result, the highly conductive subsurface zone and high temperatures observed on the ground surface were closely associated with a specific fracturing system. The latter was successfully mapped by the SP method. The SP method also defined certain fracture zones which, being highly electrically polarized, are hypothesized as future geothermal targets.All existing geophysical data have been re-evaluated, along with the SP data acquired over the geothermal field, and compared with the thermal contour maps and regional tectonics of the area.A deep borehole, drilled earlier in the area of the geothermal field, detected high temperatures in the basement (115°C), but very low flowrate of the geothermal fluids. According to the results of this study, this is due to the fact that the borehole was located outside the area of the main fracture zones of geothermal interest.     

山西省洪洞县奥陶系岩溶水地热资源评价

洪洞地热田为断陷盆地碳酸盐岩深埋低温型地热田.研究采用热储法公式计算了洪洞县奥陶系岩溶水地热资源量,并对其开展了综合利用评价,为当地地热资源的合理开发利用提供了科学依据.     

Geothermal energy potential for power generation in Turkey: A case study in Simav,Kutahya

Geothermal energy and the other renewable energy sources are becoming attractive solutions for clean and sustainable energy needs of Turkey. Geothermal energy is being used for electricity production and it has direct usage in Turkey, which is among the first five countries in the world for the geothermal direct usage applications. Although, Turkey is the second country to have the highest geothermal energy potential in Europe, the electricity production from geothermal energy is quite low. The main purpose of this study is to investigate the status of the geothermal energy for the electricity generation in Turkey. Currently, there is one geothermal power plant with an installed capacity of 20.4 MWe already operating in the Denizli–Kizildere geothermal field and another is under the construction in the Aydin–Germencik field.This study examines the potential and utilization of the existing geothermal energy resources in Kutahya–Simav region. The temperature of the geothermal fluid in the Simav–Eynal field is too high for the district heating system. Therefore, the possibility of electrical energy generation by a binary-cycle has been researched and the preliminary feasibility studies have been conducted in the field. For the environmental reasons, the working fluid used in this binary power plant has been chosen as HCFC-124. It has been concluded that the Kutahya–Simav geothermal power plant has the potential to produce an installed capacity of 2.9 MWe energy, and a minimum of 17,020 MWh/year electrical energy can be produced from this plant. As a conclusion, the pre-feasibility study indicates that the project is economically feasible and applicable.     

Investigations of deep resistivity structures at the Wairakei geothermal field

The Wairakei geothermal field was the proving ground for the use of electrical resistivity methods for geothermal exploration. At this site it was first demonstrated that a large contrast in resistivity existed between geothermal ground and the cold surroundings. Within the top 500 m of the geothermal field, low-resistivity (5–10 Ωm) reflects the effects of both the hot saline water in the pore spaces and the conductive rock-matrix. The first surveys at Wairakei used a Wenner array (a ∼550 m) to measure the resistivity values along tracks throughout the field; contour maps of the resistivities were used to estimate the lateral extent of the geothermal waters at a few hundred metres depth. In the late 1960s the Wenner array was superseded by the Schlumberger array (AB/2 = 500 m and 1000 m), which enabled deeper penetration and better definition of the extent of the geothermal waters. These early surveys showed that the bounds of the geothermal waters were often sharp, leading to the concept that a ‘resistivity boundary’ could be defined for New Zealand's liquid-dominated geothermal fields. As new methods of measuring electrical structure with greater precision became available, Wairakei was often chosen as the testing ground.     

Parabolic troughs to increase the geothermal wells flow enthalpy

This work investigates the feasibility of using parabolic trough solar field to increase the enthalpy from geothermal wells’ flow in order to increase the steam tons; in addition, it is possible to prevent silica deposition in the geothermal process. The high levels of irradiance in Northwestern Mexico make it possible to integrate a solar-geothermal hybrid system that uses two energy resources to provide steam for the geothermal cycle, like the Cerro Prieto geothermal field. The plant consists of a geothermal well, a parabolic trough solar field in series, flash separator, steam turbine and condenser. Well “408” of Cerro Prieto IV has enthalpy of 1566 kJ/kg and its quality must be increased by 10 points, which requires a Δh of 194.4 kJ/kg. Under these considerations the parabolic troughs area required will be 9250 m², with a flow of 92.4 tons per hour (25.67 kg/s). The solar field orientation is a N–S parabolic trough concentrator. The silica content in the Cerro Prieto geothermal brine causes problems for scaling at the power facility, so scale controls must be considered.     

System dynamics modelling of spring behaviour in the Orakeikorako geothermal field,New Zealand

System dynamics software STELLA is used to obtain mass and thermal balances of a spring in the Orakeikorako geothermal field, New Zealand, based on field measurements of water level, barometric pressure, rainfall and spring temperature. The model identifies the interactions of the principal influences on spring behaviour of rainfall, groundwater, geothermal steam and barometric pressure. The geothermal steam inflow estimated from the model, of about 0.022 kg/s, confirms the existence of a weak hydraulic connection with a deeper geothermal reservoir.     

A study on the optimized control strategies of geothermal heat pump system and absorption chiller‐heater

The world is becoming increasingly interested in renewable energy including geothermal energy. The utilization of geothermal systems is currently low because geothermal systems and existing source systems are used independently, but the supply rate of a geothermal system is increasing. Therefore, suggesting efficient operation plans and evaluations of the energy consumption and efficiency of a geothermal system is needed. This paper reports the results of a field study and survey of the present applications and operation conditions of a geothermal system. In addition, this paper proposes an efficient operation strategy for a geothermal system and compares this operation strategy with an existing operation strategy through simulation. The problems of existing operation condition were found out through a field study, and alternatives were proposed. The improvements were evaluated using the transient systems simulation program. And it would be possible for the reduction of the energy consumption through the comparative analysis of equipment efficiency and energy consumption. The result of analyzing the proposed combination header method through simulations compared with existing operation conditions can increase the use of geothermal systems, but the combined cooling and hot water of a geothermal heat pump and existing thermal source system reduced the efficiency of the heat pump. As a result of simulation on individual load‐sharing method, efficiency of geothermal system is increasing compared with the combination header method. This method was especially made to separate geothermal system's water loop and existing thermal source system's water loop. Copyright © 2013 John Wiley & Sons, Ltd.     

Evidence for two possible relationships between observable surface deformation and geothermal activity

During September of 1967 a large increase in the activity of a previously small geothermal field in south-western Iceland was accompanied by an earthquake swarm which lasted eight days.It is shown here, both from field observations and from the results of precise distance measurements made on a network of permanent benchmarks established soon after the seismic events, that the accompanying surface faulting shows the correct relationships with the local tectonics to be secondary shearing of the type found associated with large strike-slip faults elsewhere in the world.Vertical angle measurements on the same network of bench-marks are compared with corresponding measurements from the highly productive geothermal field at Wairakei, New Zealand, to show that the Icelandic field deforms more readily to the removal of geothermal fluids than does the New Zealand one.From this it is suggested that measurements of surface deformation in the immediate vicinity of a producing geothermal field could provide information on the gross permeability of the deep aquifers, and thus suggest how the field would behave under high discharge rates (such as would be encountered during economic exploitation).     

Geothermal energy in Phrao Basin, Chiang Mai, Thailand

Phrao Basin is famous for its geothermal and seismic activities. There are five geothermal manifestations along the western margin of the basin. These geothermal sites are probably controlled by the major fault extending northward from the Sankamphaeng geothermal field. Geological, geochemical and geophysical studies, along with 2 boreholes of 150 m depth, were aimed at investigating the potential of this area. The results indicated that the intermediate depth of the geothermal reservoir may produce enough hot fluids for various uses, albeit on a small-scale. Several industries that could be attracted to Phrao Basin by development of these geothermal areas have been identified.     

地热单井回灌渗流场理论研究

在地热开发过程中经常遇到如下问题：热储压力随开采量和时间的增加而降低，地热尾水排放造成热污染和资源浪费等。回灌是解决上述问题的有效方法。针对回灌过程中渗流场的动态变化，建立地热回灌渗流场数学模型，推导了渗透系数恒定与变化时不同条件下的单井回灌公式。实例分析表明：所得公式能够表征回灌渗流场中各变量之间的相互关系，可以解释和预测回灌过程中水头与流量的变化趋势。     

水热型地热资源地球化学勘探技术研究进展

地球化学勘探技术在水热型地热资源勘探中的应用研究具有较长的历史,迄今已形成了一套基于气体与元素指标的勘探技术体系,涵盖了众多技术指标,且已在世界各地诸多地热田勘探研究中获得了广泛应用。结果揭示,在预测地热田发育有利部位、估算深部热储温度以及推断地热水来源等方面,地球化学勘探技术都可发挥其特有的作用,是一种经济有效的地热勘探技术,具有良好的应用前景。但地热地球化学勘探技术也面临其自身的局限性,其应用研究不仅受地热田类型的限制,而且目前主要集中于已知地热田上方的验证性研究,技术本身的多解性也较强。因此,在地热地球化学勘探技术完善与应用研究方面,还有待进一步深化。     

The past, the present and the future utilization of geothermal energy in Xiong county, Hebei province, Peoples Republic of China

This paper describes the basic situation at Xiong County geothermal field, Hebei Province, China, based on a wealth of actual material. The paper then goes on to expound the distribution of the geothermal wells and the chemical composition of the geothermal water in this field, to give the geothermal utilization level of the past, the present, and to advance the future development plan— to make the Xiong County Town the first “Geothermal City” in China.     

Forecast and evaluation of hot dry rock geothermal resource in China

Utilizing information from plate tectonics characteristics, volcanic activities, and geothermal anomaly, this paper identifies areas where hot dry rock (HDR) may exist as potential geothermal resource in China. Further investigations are also carried out in the paper based on results from regional tectonics, volcanic geology and lithology, as well as data from geothermal displays, geochemistry, geophysics, and shallow borehole temperature measurements. The study reveals several promising areas of HDR geothermal resource in China, including Tengchong of Yunnan province, Qiongbei of Hainan province, Changbaishan of Jilin province, Wudalianchi of Heilongjiang province, and the Southern Tibet area. A 3D static heat conduction model was developed to study the underground temperature gradient characteristics of the Rehai geothermal field in Tengchong and the Yangbajing geothermal field in Tibet. The model adopted is a geological block 10 km deep from the ground surface and 50 km wide in each of the horizontal directions (2500 km² area). The numerical simulation results in evaluations on the quantities of the HDR geothermal resource in Rehai and Yangbajing geothermal fields. The paper shows that there is abundant HDR geothermal resource with large exploitation value in China. If developed with a power capacity of 1×10⁸ kW, the Rehai and Yangbajing fields along would be able to generate electricity for 1560 years.     

Electrical conductivity studies in the Travale geothermal field, Italy

Magnetotelluric and geomagnetic depth soundings have been carried out in the area of the Travale high enthalpy geothermal field (central Tuscany, Italy) in 1980 and 1981 to study the distribution of electrical conductivity in the geothermal anomaly and the crust beneath. Within this project the possible contributions of electromagnetic investigations to geothermal research were to be tested and a geothermal model of the Travale area was to be developed. The time-varying electric and magnetic fields have been recorded in a broad period range from 6–10,000 s, mainly on two profiles, the one parallel, the other perpendicular to the Travale graben. Strong lateral variations of apparent resistivities have been observed. Up to periods of 50–100 s the Travale graben is the dominating 2-D structure, but for longer periods of investigation the three-dimensionality of electrical conductivity structures has to be considered. The apparent resistivities inside the geothermal anomaly are extremely low, reaching not more than 50 ohm · m, even in the lower crust, but they increase to 100–300 ohm · m north of the geothermal field. Total conductance also indicates the geothermal field as a local conductivity anomaly, whereas further to the north the poorly conducting “barrier” has been confirmed. The cause of the high conductivity structures inside the geothermal area is to be seen in a highly fractured basement within this zone, allowing upward movement of hydrothermal fluids.     

Simulation of reinjection at Cerro Prieto using an idealized two-reservoir model

Most of the papers published on the hydrodynamic and thermal effects of reinjection in geothermal fields assume a single reservoir with uniform transmissivity and storativity. However, there is evidence that the Cerro Prieto geothermal field is a two-reservoir system and that each reservoir has different hydraulic properties (Abril and Noble, 1979). Because two-reservoir fields have not been adequately studied, we will analyze the thermohydrological response of this kind of geothermal system to various alternative schemes of reinjection. We use parameters relevant to the Cerro Prieto system so that the results will be useful in planning future reinjection operations at this field.     

Lumped-parameter models for low-temperature geothermal fields and their application

The behavior of low-temperature geothermal reservoirs under exploitation is simulated using analytical lumped-parameter models. These models consider the effects of fluid production and reinjection, as well as natural recharge, on the pressures (or water levels) of low-temperature, liquid-dominated geothermal systems. The computed responses for constant production/injection flow rates are given in the form of analytical expressions. Variable flow rate cases are modeled, based on the Duhamel's principle. Reservoir parameters are obtained by applying a weighted nonlinear least-squares estimation technique in which measured field data are history matched to the corresponding model response. By using history-matched models, the future performance of the reservoir can be predicted for different production/injection scenarios in order to optimize the management of a given geothermal system.We demonstrate the applicability of the models by simulating measured data from the Laugarnes geothermal field in Iceland, and the Balcova–Narlidere field in Turkey.     

Isotopic zoning and origin of the aquifers in the discharge area of the geothermal fields of ahuachapán and Chipilapa, El Salvador

The northern discharge areas of the Ahuachapán, and Chipilapa geothermal fields can be subdivided into four different zones based on their structural position, and the isotopic and chemical composition of their waters. In general, the contribution of geothermal waters from these two fields was estimated to be less than 10%. Elevation effects are of little importance, whereas a slight trend towards higher isotopic values with increasing water temperatures may exist.The NNW-SSE-trending Escalante and Agua Caliente faults represent lateral groundwater barriers, and provide vertical conduits for the ascending geothermal waters. The western discharge areas seem to be more influenced by the Ahuachapán, geothermal field, whereas those to the east are more influenced by the Chipilapa field.Groundwaters in the Northern Plain are mainly from shallow northward-flowing aquifers. These waters show temperature effects, mixing with geothermal waters and are affected by the geology of the area. However, none of these factors alone can explain the isotopic variations observed in the waters of the northern discharge areas.     

地热发电的投资经济分析

地热能是一种清洁的可再生能源,越来越多的国家宣布支持地热开发。地热发电必须考虑到影响成本的各种因素,地热发电的成本主要由初始投资和电力生产运行及维护成本两部分组成。地热项目具体的投资成本与资源特征和现场条件有着非常密切的关系,资源的温度、深度、化学特性和渗透性是影响发电成本的主要因素。与传统化石燃料发电相比,地热发电已具有相当的竞争力,在生命周期内地热发电厂的平均成本大大低于传统燃料发电厂。另外,地热发电还有抵消化石燃料价格波动对电力市场影响的作用,有利于促进农村和偏远地区经济发展,有利于能源供应多元化。当然,地热能发展也面临着一些障碍,包括钻井的成功率、地热技术尚不够完善以及项目启动成本高等。建议今后地热资源的利用不再仅局限于极少数高温地热项目中,而是尽可能发掘地热资源的所有潜力。     

Geothermal development in Nicaragua

In order to meet national energy requirements, Nicaragua has had to direct its attention towards sources of “alternative energy”, such as geothermal. Excellent geothermal prospects exist in this country, for which reason the Revolutionary Government has deemed it convenient to direct its energy policy towards this alternative source. Studies carried out during past years have led to the selection of nine areas in western Nicaragua, four of which were earmarked Very High Priority because they contain high enthalpy geothermal fields, three areas were earmarked High Priority and only two Low Priority. The positive results obtained in the Momotombo geothermal project have become an incentive to continue research and development nation-wide.At present, a power plant is operating with 35 MW at the Momotombo geothermal field; another 35 MW power plant is under construction in the same field; the El Hoyo-Monte Galan project is in the pre-feasibility phase and surveys are under way throughout national territory.