Geophysical investigations of the Seferihisar geothermal area, Western Anatolia, Turkey

Self-potential (SP), magnetic and very low frequency electromagnetic (EM-VLF) surveys were carried out in the Seferihisar geothermal area to identify major and minor fault zones and characterize the geothermal system. The SP study provided useful information on the local faults and subsurface fluid flow. The main SP anomalies appear mostly along and near active fault zones in the area of the Cumalı, Tuzla and Doğanbey hot springs. Two of these anomalies near the Tuzla hot springs were further evaluated by SP modelling. Total magnetic field values increase from the Doğanbey to the Cumalı hot springs. Modelling performed on the magnetic data indicates that between these two spring areas are four different regions or units that can be distinguished on the basis of their magnetic susceptibility values. Fraser filtering of EM-VLF data also indicates that there are three significant conductive zones in the regions around the Cumalı, Tuzla and Doğanbey hot springs, and that they lie between important fault systems. The EM-VLF and total (stacked) SP data show that the conductive tilt anomalies obtained by Fraser filtering generally coincide with negative SP areas.According to our geophysical investigations, new exploratory wells should be drilled into the conductive zones located between the Cumalı and Tuzla hot springs. We further recommend that resistivity and magnetotelluric methods be carried out in the area to obtain additional information on the Seferihisar geothermal system.     

Geothermal energy in Turkey: 2008 update

Geological studies indicate that the most important geothermal systems of western Turkey are located in the major grabens of the Menderes Metamorphic Massif, while those that are associated with local volcanism are more common in the central and eastern parts of the country. The present (2008) installed geothermal power generation capacity in Turkey is about 32.65 MWe, while that of direct use projects is around 795 MWt. Eleven major, high-to-medium enthalpy fields in western part of the country have 570 MWe of proven, 905 MWe of probable and 1389 MWe of possible geothermal reserves for power generation. In spite of the complex legal issues related to the development of Turkey's geothermal resources, their use is expected to increase in the future, particularly for electricity generation and for greenhouse heating.     

Geothermal resources of Hachijojima

Hachijojima is a gourd-shaped volcanic island in the Pacific Ocean. Nishiyama and Higashiyama volcanoes consist of basalt lava and associated pyroclastic rocks. A promising geothermal resource was found in south Higashiyama, associated with an uplift of Tertiary rocks consisting of mainly andesite lava and related pyroclastic rocks, overlain by Quaternary volcanic rocks. Steep high-temperature (over 250°C) and high-pressure gradients occur in the deeper portion of the system near the Tertiary–Quaternary contact, indicating the presence of a cap rock. The cap rock formed by deposition of hydrothermal minerals. Geothermal fluid ascends from the deeper portions to shallow depths along vertical fractures through the cap rock. These vertical fractures form the geothermal reservoir in the Tertiary formation. Three wells were drilled into these vertical fractures, and approximately 30 t/h of superheated steam was obtained from each well during flow tests. The geothermal fluid is mainly a mixture of seawater and meteoric water in an approximate ratio of 1 to 2, based on chemical analyses, with a portion of volcanic gas included. At present a 3.3 MW_e, geothermal power plant is being constructed here.     

Geothermal applications in Turkey

Geothermal energy is mostly utilised in direct applications in Turkey. The equivalent of 61,000 residences are currently heated by geothermal fluids. A total of 665 MW_t is utilised for space heating of residential, public and private property, and 565,000 m² of greenhouses. Geothermal fluids are also used in 195 spas (327 MW_t), bringing the total direct use capacity to 992 MW_t. ORME Geothermal Inc. has completed the engineering design of a geothermal district heating system that serves the equivalent of nearly 300,000 residences. A total of 170 geothermal fields have been explored so far in Turkey. At Kizildere a single-flash power plant with 20.4 MW_e installed capacity is integrated with a factory producing liquid CO₂ and dry-ice. A binary cycle power plant with an installed capacity of 25 MW_e will be constructed shortly at Aydin/Germencik. The proven geothermal heat capacity, according to data from existing geothermal wells and natural discharges, is 3132 MW_t (I. Akkus, MTA General Directorate, oral communication, January 2003).     

Research on the generation of electricity from the geothermal resources in Simav region, Turkey

One of the greatest problems in using renewable energy sources is the great variability of energy level, both in the short and long term. Geothermal energy, by nature, has high availability because the source is not dependent on weather conditions, so it is among the most stable renewable energy sources. Geothermal energy has the potential to play an important role in the future energy supply of Turkey. Although Turkey has the second-highest geothermal energy potential in Europe, electricity generation from geothermal energy is rather low.This study examines the use of geothermal energy in electricity generation and investigates the applicability of the existent geothermal energy resources to electricity generation in the Kütahya–Simav region, Turkey. The binary cycle is used in the designed power plant for electricity generation from geothermal fluid in which the percentage of liquid is high and which is at lower temperature. In this power plant, R134a is chosen as the secondary fluid, whose boiling point temperature is lower than that of water, and is used instead of geothermal fluid in a second cycle. The thermal efficiency of the designed power plant is measured to be 12.93%.     

Power generation from geothermal resources in Turkey

This study provides information on power generation via geothermal resources and sector development. The first instance of power generation from geothermal resources was performed by a state-owned power plant at Kızıldere-Denizli, whereas the first private sector investment was the Dora-I power plant, commissioned in 2006. Legislation regulating rights ownership and certification laws was issued in 2007. The installed capacity of the geothermal resources is 311.871 MW for 16 power plants, and power generation licenses were issued for 713.541 MW at the end of 2012. The total potential geothermal power that can be generated in Turkey is estimated to be approximately 2000 MW. The geothermal fields in Turkey produce high levels of greenhouse gases, which have been deemed highly responsible for global warming. Due to high CO₂ emissions, the geothermal energy sector risks a carbon tax in the near future. For certain geothermal resources, multiple investors produce electricity from the same resource. The sector will inevitably experience severe damage unless permanent solutions are devised for problems related to sustainably managing geothermal resources and environmental problems.     

A snapshot of geothermal energy potential and utilization in Turkey

Turkey is one of the countries with significant potential in geothermal energy. It is estimated that if Turkey utilizes all of her geothermal potential, she can meet 14% of her total energy need (heat and electricity) from geothermal sources. Therefore, today geothermal energy is an attractive option in Turkey to replace fossil fuels. Besides, increase in negative effects of fossil fuels on the environment has forced many countries, including Turkey, to use renewable energy sources. Also, Turkey is an energy importing country; more than two-thirds of her energy requirement is supplied by imports. In this context, geothermal energy appears to be one of the most efficient and effective solutions for sustainable energy development and environmental pollution prevention in Turkey. Since geothermal energy will be used more and more in the future, its current potential, usage, and assessment in Turkey is the focus of the present study. The paper not only presents a review of the potential and utilization of the geothermal energy in Turkey but also provides some guidelines for policy makers.     

Current Geothermal Energy Potential in Turkey and Use of Geothermal Energy

Turkey is the seventh-richest country in the world in geothermal potential. The first geothermal researches and investigations in Turkey started by the Turkey Mineral Research and Exploration Institute (MTA) in the 1960s. Upon this, 170 geothermal fields have been discovered by MTA, in which 95% of them are low-medium enthalpy fields, which are suitable mostly for direct-use applications. The overall geothermal potential in Turkey is about 38,000 MW. Of this potential, around 88% is appropriate for thermal use (temperature less than 473 K) and the remainder is appropriate for electricity production (temperature more than 473 K). Turkey has extended its involvement in geothermal energy projects, supported by loans from the Ministry of Environment, and geothermal energy is expected to increase substantially in the coming years. Overall, Turkey has an estimated 4,500 MW of geothermal power production potential.     

Hydrogeological and isotopic survey of geothermal fields in the Buyuk Menderes graben, Turkey

The main high and low enthalpy geothermal fields in the Buyuk Menderes graben (Western Anatolia) and their reservoir temperatures are as follows: Kizildere (242 °C), Germencik (232 °C), Aydin-Ilicabasi (101 °C), Yılmazkoy (142 °C), Salavatli (171 °C), Soke (26 °C), Denizli -Pamukkale (36 °C), Karahayit (59 °C), Golemezli (101 °C) and Yenice (70 °C). The geothermal systems are controlled by active graben faults. The reservoir rocks in the geothermal fields are the limestone and conglomerate units within Neogene sediments and the marble-quartzite units within Paleozoic metamorphic formations. There are clear δ¹⁸O shifts from the Mediterranean Meteoric Water Line (MMWL) in the Kizildere, Germencik and Aydin fields, where a good relation between high temperatures and δ¹⁸O shift has also been observed, indicating deep circulation and water rock interactions. In the Pamukkale, Karahayit, Golemezli and Yenice fields and in Soke region, low temperatures, small isotope shifts, shallow circulations and mixing with shallow cold water have been noted.     

Geophysics in geothermal prospecting

Geophysical prospecting of high temperature geothermal reservoirs aims at identifying either fluid trapping structures or anomalies related to the properties of the hydrothermal fluid and rock to fluid interactions. Two types of reservoir environments can be characterized: (i) sedimentary reservoirs when a carbonate reservoir is generally capped by a dominantly argillaceous, hydraulically impervious and thermally insulating cover, and (ii) volcanic and volcano-sedimentary reservoirs associated with hydrothermally altered areas. Based on the aforementioned exploration goals and reservoir settings, a wide spectrum of geophysical methods can be applied whose selection is largely commanded by local geological conditions and expected reservoir morphology. Major geophysical techniques are reviewed and their potential, as to geothermal reservoir prospecting issues, discussed.     

Hydrogeological and geochemical studies of the Efteni and Derdin geothermal areas,Turkey

The Efteni and Derdin geothermal areas are located in northwestern Turkey. Relatively low-temperature springs emerge from the Duzce Fault, a normal-component-dominated fault segment of the North Anatolian Fault System. The thermal waters of the Efteni and Derdin Springs show distinct geochemical and isotopic characteristics since they originate from different geothermal reservoirs and reflect the effects of different water–rock interaction processes. Geothermometry revealed higher reservoir temperatures for the Efteni system, however a strong δ¹⁸O shift, interpreted as being the result of isotopic exchange at high temperatures, was observed in the Derdin system. Hydrogeological and geochemical techniques are applied to identify recharge mechanisms, water–rock interaction processes and to construct conceptual models of these geothermal systems.     

Geothermal energy in Kenya

Kenya has joined the list of countries that generate electricity from geothermal sources. A 15 MW geothermal station at Olkaria, near Lake Naivasha in the Rift Valley, began operating in August 1981 and is already providing Kenya with 7% of its electricity needs, at an economic cost.     

Geothermal exploration of kos island, Greece: Magnetotelluric and microseismicity studies

This paper reports the results of magnetotelluric (MT) and microseismicity studies, conducted as part of a multi-disciplinary project to explore the geothermal potential of the island of Kos, Greece. The MT survey, comprising 18 soundings, was carried out in the bandwidth 128 Hz–40 s, in order to determine the deep conductivity structure in the geothermally prospective western part of the island. Rigorous dimensionality analysis has indicated that the geoelectric structure could adequately be approximated with 1-D interpretation tools. Two significant and seemingly communicating conductive zones of potential geothermal interest were found within the first 2 km. The first is extensive and shallow, detected at depths of 400–600 m; the second is deeper (1000–1300 m), but of considerably smaller lateral dimensions. A very deep relative conductor (<25 Ωm) was also detected at depths of 7–10 km, which is thought to comprise part of an old magma chamber with brine-saturated rocks. The microseismicity studies revealed the partial or total attenuation of shear waves in many microearthquake records. The analysis of these observations determined the vertical and lateral extent of that attenuation zone, the greatest part of which is located underneath the marine area between western Kos and Nissyros island to the south, extending approximately from near the surface to about 1.5 km depth. The nature of this zone is discussed in terms of fluid concentration due to the geothermal system of the area.     

Shallow submarine and subaerial, low-enthalpy hydrothermal manifestations in Punta Banda, Baja California, Mexico: Geophysical and geochemical characterization

The low-enthalpy geothermal system at Punta Banda (NW Baja California Peninsula, Mexico) has been studied because it might provide heat to future desalination plants in the city of Ensenada. Utilization of subaerial, intertidal and submarine hot springs is evaluated based on geochemical and geophysical data. The results of the geochemical studies show that the geothermal fluids have a major meteoric water component because seawater is not present at the subaerial springs and hot wells. The highest estimated reservoir temperature (140 °C) calculated using a silica geothermometer corresponds to the Agua Caliente intertidal manifestation, a promising area also identified by geophysics. Geothermometric calculations applied to the computed composition of the thermal end member yield a reservoir temperature of 137 °C. Cl/B ratios indicate that the thermal fluids discharged by the intertidal vents and subaerial springs are similar, but they differ from those of submarine vents. Geoelectrical models depict an anomalous conductive trend from the La Jolla well to the Agua Caliente manifestation, suggesting the presence of a fault that allows upflow of hot water from depth. Lastly, integration of geochemical and geophysical data identified the best site for future exploration drilling at Punta Banda.     

Geothermal resource development in agriculture in Kebili region, Southern Tunisia

Geothermal energy in the Kebili region, south of Tunisia, is used in a number of applications, but mainly in agriculture. Approximately 95% of the thermal water is used for irrigation of oases and heating greenhouses. Generally, when the water temperature is less than 40–45 °C it is used directly for irrigation, but when it exceeds 45 °C it is cooled by means of atmospheric towers before being used to irrigate 16,000 hectares of oases (half of the total area of the oases in Tunisia). Geothermal energy is also used for heating and irrigating greenhouses, which are considered promising and economically feasible applications. The total area of heated greenhouses in the country has increased considerably and is today at 103 ha, 44% of which are located in the Kebili area. Utilization of the geothermal resources will, without a doubt, increase in the near future once we have implemented the last phase of the greenhouse project. By the end of 2003, 13 ha will be added in the region, representing an increase of 29%.     

Geothermal energy: Non-electric potential in the USA

In this paper, the authors examine the energy market potential of non-electric uses of hydrothermal geothermal in the USA during the period 1985–1995. A generalized pricing model is developed for estimating a future delivered price of geothermal energy for a wide range of uses. These prices are then compared with forecast prices of alternative fuels. Market potential is then calculated as the sum of the energy demands of consumers for whom geothermal is at least price competitive. A modest contribution, one which is sensitive to government support, is expected from geothermal during the forecast period.     

Geothermal resources in Iran: The sustainable future

Because of disadvantages of fossil fuels, renewable energy sources are getting importance for sustainable energy development and environmental protection. Among the renewable sources, Iran has geothermal energy potential. The Iranian government is considerable attention to the utilization of renewable energy, especially wind, solar and geothermal energies. Due to recent advancements in geothermal energy, many investors in the country have become interested in investing in this type of energy. Geothermal studies in Iran started in 1975 with a cooperative between the ministry of Energy of Iran and ENEL Company from Italy. Preliminary studies indicated potential for geothermal power generation in four areas in northern Iran (Khoy-Maku, Sabalan, Sahand and Damavand at Azarbaijan Gharbi, Ardebil, Azarbaijan Sharghi and Tehran provinces), respectively. Geothermal development in Iran has gained momentum in the last five years with increased exploration and industry growth in the country. Iran is developing a geothermal plant for power production. Iran government plans to build 2000 MW of renewable energy capacity over the next five years. Total projected use (geothermal capacity) has been estimated 100 MW at the end of 2010. Exploration drilling is currently in-progress for Meshkinshahr project in North-Western Iran. The Sabalan geothermal power plant is expected to produce 50 MW electric powers in 2011. The plants are planned by Iran Ministry of Energy and the Renewable Energy Organization of Iran (SUNA). This study presents a brief introduction to the resource, status and prospect of geothermal energy in Iran.     

Evaluation of the reconnaissance results in geothermal exploration using GIS

Geographical Information System (GIS) is used to determine the spatial association between geophysical and geological evidence and production zones in a well-known geothermal field (Los Azufres, Mexico). Surface observations in Los Azufres were used to delineate areas characterized by high permeability and hot fluid transport from the reservoir: main faults, superficial fracture density, surface manifestations, contacts with the most recent rhyolite domes, and low values in the apparent resistivity surveys. Three knowledge-driven models were constructed based on a conceptual model of the field: a hydrothermal system in rough terrain with secondary permeability. Boolean, Index Overlay and Fuzzy scheme models were proposed and the results obtained show a good correlation with the location of the producing and non-producing wells that have been drilled in the field. The results obtained are useful for well siting (Boolean and Low-Risk Fuzzy models) or for planning further detailed exploration (Index Overlay and High-Risk Fuzzy models).     

Partitioning of rare earths and some major elements in the Kizildere geothermal field, Turkey

Rare earth elements and yttrium (REY), Na⁺, K⁺, Cl⁻, and Ca²⁺ were determined in water, steam, mineral scale and rock samples from the Kizildere geothermal field, Turkey. The CO₂-rich parent fluid originates from a sequence of mica schists with marble intercalations. The chemistry of the parent fluid varies with location and time. The average REY composition of the fluids is derived by extrapolation to the lowest Ca concentrations. The apparent vapor–liquid partitioning factors for REY at 145 °C and 5 bar total absolute pressure are about 0.2, whereas for Ca²⁺, Na⁺, K⁺ and Cl⁻ they are <0.05, about 0.0005, 0.0005 and about 0.02, respectively. Apparent scale-liquid distribution coefficients for REY at 145 and 190 °C are about 0.15 and 0.55, whereas at 100 °C they increase from 0.3 (La) to 1.5 (Lu).