The Germencik Omerbeyli geothermal field is considered to be one of the most important geothermal fields in Turkey. A numerical modeling study was carried out to simulate the response of the field to different production/injection scenarios. The reservoir performance evaluation was based on the numerical simulation of the reservoir behavior using the simulation code TOUGH2. The numerical simulation model includes a total area of 85.8 km2 and extends from the surface at +330 m msl (mean sea level) to a depth of -4581 m msl. Through a trial and error process, the natural state model was satisfactorily matched with the initial temperature and pressure data measured at the wells. The natural state model was further calibrated using the long term flow test (LTFT) data conducted in 2006, including OB-6 and OB-9 as flowing wells and OB-8 as an injection well. The model was then used to predict reservoir performance under different production/injection scenarios over the next 30 years. Forecast runs showed that the pressure declines almost equally in all areas, consistent with the high permeability and connectivity of the reservoir, which had been established from the LTFT.

The aim of this study is to construct a numerical reservoir model for Bal&ccedil / ova geothermal field, which is located in the izmir bay area of the Aegean coast. A commercial numerical simulation program, TOUGH2 was utilized with a graphical interface, PETRASIM to model the Bal&ccedil / ova geothermal field. Natural state modeling of the field was carried out based on the conceptual model of the field, then history matching of production &ndash / injection practices of the field was established for the period of 1996 &ndash / 2008. The final stage of modeling was the future performance prediction of the field by using three different Scenarios. In Scenario-1, production and injection rates in year 2008 were repeated for 20 years. In Scenario-2, production and injection rates in year 2008 were repeated for the first 3 years, then they were increased at every 3 years. In Scenario-3, a new well (BT-1) that is assumed to be drilled to 1000 m depth is added for injecting some portion of water that was injected through BD-8 well. In that scenario, similar to Scenario-2, production and injection rates in year 2008 were repeated during the first 3 years, and then the rates of these wells (except the new well) were increased every three years. Analysis of the results indicated that in Scenario-2, compared to Scenario-1, both the temperatures of deep wells located at the eastern portion of the field (BD-6, BD-2, BD-14, BD-9, BD-11, BD-12) and the temperatures of deep wells located at the western portion (BD-4, BD-15, BD-7, BD-5) decreased more. In Scenario-3, compared to Scenario-1, the deep wells located at the eastern side experienced less temperature drops while the deep wells located at the western side experienced higher temperature drops. Such temperature differences were not encountered in shallow wells. No significant changes in bottom hole pressures of deep wells occurred in all three scenarios. On the other hand, shallow wells, especially B-10 and B-5, responded to Scenario-2 and Scenario-3 as decrease in bottom hole pressures.

Formation temperature is an important parameter in geothermal drilling since it affects all the components of the system such as drilling fluid, drilling operations and equipment through mud temperatures. The main objective of this study is to estimate the formation temperatures of five geothermal wells in Germencik-&Ouml / merbeyli geothermal field by using inlet and outlet mud temperatures obtained during drilling. For this purpose, GTEMP, a wellbore thermal simulation model is used to simulate the process of drilling and to estimate the formation and bit temperatures of five wells. With the formation and bit temperature estimations of GTEMP and inlet and outlet mud temperature data from field / temperatures vs. depth graphs are plotted for five wells for two cases. In Case 1, cooling tower effect on mud temperatures is neglected whereas in Case 2 it is taken into account. For the estimation of formation temperature of the final depth, Case 2 showed better results with % 1,5-24,5 deviation compared to the % 3,6-25,2 deviation obtained in Case 1.

Edremit geothermal field with 42-62 &deg / C discharge temperatures is utilized for space heating. Alternation of permeable and impermeable units created two superimposed aquifers in the area: upper unconfined and lower confined. Water samples from 21 (hot, warm, cold) wells were taken in this study. 8 of these wells penetrate the deeper confined, while 13 penetrate the shallower unconfined aquifer. Geochemical analysis revealed Na+K&ndash / SO4 nature for the hot (&gt / 40&deg / C), Ca&ndash / HCO3 nature for the cold (&lt / 30&deg / C) and Ca&ndash / SO4 nature for the warm (30-40&deg / C) waters. &delta / 18O-&delta / D compositions point to a meteoric origin for all waters, while 14C analyses suggest longer subsurface residence times for the hot, compared to the cold/warm waters. Chemical and isotopic compositions indicate that &ldquo / mixing&rdquo / and &ldquo / water-rock interaction&rdquo / are the possible subsurface processes. When silica and cation geothermometers are evaluated together with fluid mineral equilibria calculations, a 110&deg / C reservoir temperature is expected in the field. Saturation indices indicate potential silica scaling for waters at temperatures lower than discharge temperatures. Hydrogeology of the study area is highly affected by faults. The groundwater is percolated (down to 3 km depth) via deep seated step faults, heated at depth and ascends to surface at the low lands, especially through intersection of buried, mid-graben faults. During its ascent towards surface, geothermal water invades the two superimposed aquifers and mixing between hot and cold waters takes place in the aquifers. Resource assessment studies suggest a 3.45x1013 kJ accessible resource base and 9.1 MWt recoverable heat energy for Edremit geothermal field with 90% probability.

In September 2009 exploratory testing of an old geothermal power well caused a blowout at the El Tatio geothermal field of northern Chile. El Tatio is the largest geyser field in the southern hemisphere. The blowout was a paradigm-shifting event for the management of the El Tatio geothermal field and drew attention to the disparity and critical nature of scientific information sharing. This study uses the El Tatio incident as a case study for examining problems of common-pool resource management and geothermal energy development. It explores how differing valuations of geothermal resources resulted in a breakdown of coherent regulation and negative outcomes for all stakeholders. Contingent valuation methods were used to create an elicitive interview process in order to assess how differences in valuation drove these conflicts and negative outcomes. The sharing of scientific information through Decision Support Systems (DSS) is identified as an important element in resolving these conflicts and creating new policies for common-pool resource management. These methods are presented as tools that can be used by stakeholders to find common ground and seek mutually beneficial outcomes. In addition, these tools can help with the critical issue of social perception of scientific data and science driven solutions to these problems. This study posits that the path forward is to ensure not only that scientific data is communicated in modes appropriate to the community and problem at hand, but that the acquisition and interpretation of this data is informed by stakeholder needs. / text

Lichen have been used as indicators of atmospheric pollutants since Grindon (1859) observed lichen populations declining in a polluted Southern Lancashire in the mid-1800s. Since then lichen have been used in a number of atmospheric studies. A study by Tozer et al. (2005) attempted to use nitrogen isotopes of lichen and free-living algae as indicators of geothermal ‘pollution’ near Rotorua and the Te Kopia Geothermal Area, but was unable to show a correlation with distance to geothermal features. This thesis aims to build from Tozer et al. (2005) and use both carbon and nitrogen isotopes in lichen as an exploration tool in geothermal areas. Three transects were completed: one across the South Island from Christchurch to Greymouth (non-geothermally influenced area), and two along (north-south) and across (east-west) the Taupo Volcanic Zone (TVZ) in the North Island (geothermally influenced area). In addition to these three transects, sampling at higher spatial resolution was conducted in the immediate vicinity of the Orakonui Stream geothermal springs at the Ngatamariki Geothermal Area. The three transects showed large variation, largely due to the type of land use from which the sample was collected. The highest nitrogen contents (1.62 ± 0.39%) and less negative nitrogen isotopic compositions (-9.44 ± 0.39‰) were found over farmland, while both exotic and native forests had low nitrogen (1.08 ± 0.35% and 1.03 ± 0.44‰, respectively) and highly negative isotopic compositions (-12.94 ± 0.26‰ and -12.09 ± 0.45‰, respectively). The statistical difference between land use classes is hypothetically explained by variations in nitrogen sources, with intensive farmland volatilizing NH3 with δ15N values of -6 to -10‰ (Tozer et al., 2005), while forest areas are expected to produce biogenic nitrogen from decomposition with more negative δ15N. At Ngatamariki, δ13C and δ15N isoscapes were produced, with both showing a large isotopic anomaly (>-23.5 and >-8‰, respectively) to the north and north-west of the study area, correlating with areas of farmland, although in some places the δ15N values exceed 0‰, which is unexplained. A study by Hanson (2014) identified diffuse soil flux using δ13C in the vicinity of the Orakonui South Main Crater to have a geothermal signature, the same location in which a small relatively less-negative δ13C anomaly (>-23.5‰) is seen in lichen isotopes. While this could be attributed to a geothermal influence, it could also be due to the effect of substrate the lichen lives on and a reduction in carbon sourced from biogenic respiration. Ultimately, there is the potential for isotopes in lichen to be used as a geothermal exploration tool, although this method needs to be investigated in a higher flux geothermal area, such as Rotokawa, 7km to the south of Ngatamariki.

Thermal stimulation of geothermal wells is a production enhancement technique that is an attractive option to operators of geothermal fields as a way to enhance and revitalize well performance capabilities through injection of cold water into the geothermal reservoir. This thesis presents a review of thermal stimulation procedures that have been carried out at various geothermal fields worldwide, and then sets out to demonstrate through laboratory experiments the effects of thermal stimulation on typical reservoir rocks. Thermal damage to crustal rocks is important in many fields of practical engineering applications. Thermal fractures have been discussed in many studies, however their formation under fully water saturated conditions as a result of rapid quenching is not fully understood. In this study, a new methodology is designed to replicate thermal stimulation in such an environment, using an apparatus that allows rocks to be heated to 350°C at up to 22 MPa confining pressure and rapidly quenched with cold water to ambient temperature while maintaining system pressure. The results indicate that through thermal cycling in the apparatus, porosity was increased, density decreased, acoustic velocities attenuated and mechanical properties significantly altered. Maximum damage occurred during the first thermal cycle, a product of the thermo-mechanical Kaiser effect such that rocks should not experience additional damage unless a previous maximum stress is surpassed. The thesis details a comprehensive evaluation of the Rotokawa Andesite sourced from the Rotokawa Geothermal field located in the Taupo Volcanic Zone, New Zealand. The importance of microstructural fabrics on the physical properties of this reservoir lithology is demonstrated. The mineralogical and petrological fabrics of the rocks are coupled with detailed studies of the microstructural fracture networks, including measurements of porosity, density and permeability. Acoustic wave velocities and dynamic elastic moduli were determined. Uniaxial compressive strength testing coupled with acoustic emission have helped to determine the behavior of the rock under deformation and provided data to characterize the static elastic moduli of the rocks. These data are then utilized to build empirical, micromechanical and geometric relationships. To better constrain important engineering concerns such as wellbore stability, reservoir forecasting and stimulation procedures, thermal property measurements were carried out on samples recovered from the Rotokawa Andesite. In particular, measurements of linear thermal expansion, thermogravimetric analysis, and differential scanning calorimetry were measured utilizing varied experimental heating rates of 2, 5 and 20 K/min. The property analyses were carried out to determine if heating rates influenced the measurement of thermal properties, specifically thermal expansion coefficients and strain rate in the samples. Results indicate that thermal expansion is not heating rate dependent within the range investigated though the strain rate is significantly dependent on heating rate, with higher strain rates observed in conjunction with higher heating rates. By using a one dimensional stress model, a failure criterion can be established for the Rotokawa Andesite when subject to thermal stressing. The importance of this study is to further understand the critical heating and cooling rates at which thermal stress causes cracking within the Rotokawa reservoir. This can enhance permeability but can also affect wellbore stability, so constraining these conditions can be beneficial to resource utilization. To test effects of thermal stimulation in the laboratory, Rotokawa Andesite core was heated to 325ºC at pressure of 20 MPa and quenched rapidly to 20ºC while maintaining a pressure of 20 MPa. Permeability increased by an order of magnitude over original pre-treatment values. Ultrasonic velocities also reflected a significant change after stimulation testing. Scanning electron microscopy showed significant microstructural change to samples and supplemented physical property investigations. The results imply that thermal stimulation can be successfully repeated in the laboratory and is coupled with both thermal and chemical components. The results of these investigations are of profound importance for effective utilization and maintenance of the Rotokawa Geothermal field and the results also have implications for geothermal fields worldwide.

How to exploit and make use of natural gas hydrates in oceans will weigh much in the future researches. Unlike the oil or gas reservoirs, the distributions of natural gas hydrate are very complicated and don’t congregate massively in oceanic sediments. Besides, factors such as seafloor geohazards and climate must be taken into account, which makes it much more difficult and complicated to exploit oceanic gas hydrates than conventional oil or gas. Nowadays neither of such methods as thermal stimulation, depressurization, inhibitor injection, carbon dioxide replacement and mixing exploitation etc. is applied to exploit gas hydrates in marine sediments because of their disadvantages. This paper introduces a conception of combining solar and geothermal energy for gas hydrates exploitation. The model mainly includes five parts: solar energy transferring module, sea water circulating module, underground boiler module, platform and gas-liquid separating module. Solar cells and electric heaters are used to heat the formations containing hydrates. Because they become relatively more mature and cheaper, it’s the key of how to utilize the geothermy to exchange heat in developing this conception, which needs solution of fluid leakage, circulating passages and heat-exchange interface problems in building underground boiler. Probably it’s a feasible measure to use an effective hydraulic control system and hydraulic fracturing. The idea should be a good choice to exploit marine gas hydrates by combining solar and geothermal energy since this method has a great advantage either in terms of efficiency or cost.

Vakarų Lietuvoje aptikus padidėjusį šilumos srautą, imta domėtis geoterminės energetikos perspektyvomis. Išmatavus geoterminės anomalijos zonos savybes pastebėta, kad šioje zonoje vyraujantis šilumos srautas yra dvigubai didesnis, nei likusioje Lietuvos teritorijoje ir yra dvigubai didesnis už vidutinį rytų Europos šilumos srautą, o aukštesnės nei 150 ºC temperatūros yra pasiekiamos kristalinio pamato uolienose. Pirminiai geoterminės anomalijos parametrai yra nustatomi geofizinių ir geocheminių metodų pagalba. Kiti parametrai – gręžinio eksploatacijos metu. Šių parametrų ţinojimas nulemia tolimesnę patobulintos geoterminės sistemos (Enhanced geothermal system, EGS) kūrimą. Aukšto slėgio geoterminis skystis spaudžiamas į porėtą uoliena, sąveikauja su ją sudarančiais mineralais ir deformuoja ją hidrosuplėšymo metu, taip praplėsdamas ir atverdamas naujus plyšius. Ši technologija yra vadinama stimuliuota sausų uolienų geoterminė sistema (Hot dry rock, HDR). Šių sistemų tikslas yra poţeminio šilumokaičio sukūrimas, pumpuojant aukšto slėgio vandens srautą į kristalinį pamatą. Taip formuojamas stimuliuotų plyšių koridorius, kuriuo cirkuliuoja gręžiniais pumpuojamas vanduo. / The geothermal energetic was found interesting for an anomalous heat flow at the west Lithuanian that is the most intense in a whole East European Platform. A higher temperature than 150 ºC is available in crystal basement at Lithuania at less than 5 km depth. To measure basic parameters of geothermal anomaly, geophysical and geochemical methods are applied. The other measurements are taken at the moment of hydrocirculation. Knowledge of these parameters will be used for the development and improvement of the enhanced geothermal system (EGS). High pressured water geothermal fluid is pumped into the rock in purpose to open old and create new cracks and fractures by exceeding rock compressive stress. For this reason there was created hot dry rock (HDR) system. The main goal of this system is to create a geothermal reservoir by pumping high pressure water flow into the rock. This way water circulates in enhanced geothermal system through the tunnel of fractures.

Baigiamajame magistro darbe nagrinėjamas pastato, aprūpinimas šiluma šilumos siurbliu su šiluminiais poliais. Yra apžvelgtos esamos giliosios bei sekliosios geoterminės energijos panaudojimo panaudojimo galimybės Lietuvoje. Aprašytos prielaidos ir supaprastinimai šiluminių polių skaičiavimui, aprašytos skaičiavimo metodikos. Atlikti šiluminių polių skaičiavimai, naudojantis penkiomis metodikomis. Aprašytas pasirinktas pastatas, apskaičiuoti atitvarų šiluminiai rodikliai, nustatyta pastatui reikalinga šiluminė galia. Naudojantis „Design builder“ modeliavimo programa sukurtas pastato modelis ir apskaičiuoti pastato šilumos bei vėsos poreikiai metų laikotarpiu. Pagal nustatytus poreikius modeliavimo programa „EED“ sumodeliuoti šildymo vėsinimo ciklai dvidešimt penkeriems metams į priekį. Sistema palyginta su baziniu šilumos šaltiniu. Išnagrinėjus gautus rezultatus pateikiamos rekomendacijos bei baigiamojo darbo išvados. Darbą sudaro 11 dalių: įvadas, geoterminės energijos panaudojimo galimybės Lietuvoje, šilumos siurblių tipai, šiluminių polių skaičiavimo metodikos bei skaičiavimai, nagrinėjamo pastato aprašymas, pastato šiluminės galios skaičiavimas, pastato šilumos/vėsos poreikių modeliavimas „Design builder“ programa, šiluminių polių skaičiavimas „EED“ programa, nagrinėjamos sistemos palyginimas su baziniu šilumos šaltiniu, rekomendacijos, išvados ir literatūros sąrašas. Darbo apimtis 68 p. teksto be priedų, 49 iliustr., 16 lent., 29 literatūros šaltiniai. / The final master thesis presents analysis of heat supply to the building using a heat pump with energy piles. There is an overview of shallow and deep geothermal energy utilization current possibilities in Lithuania. The assumptions and simplifications of the calculation for the energy piles are described as well as the calculation methodology. Calculations of the energy piles are performed, using five methods. The chosen building is described, thermal performance of partitions are calculated and the building heating capacity is calculated. . Using the "Design Builder" building simulation program a model was generated and the calculations of annual heating and cooling demand are performed. According to the demand of building using simulation program "EED" heating /cooling cycles are calculated of twenty-five years ahead. The system was compared with the basic heat source. After analyzing all results conclusions are given. Thesis consists of 11 parts: introduction, overview of geothermal energy resources usage posibilities in Lithuania, types of heat pumps, calculation methods and calculations of energy piles, description of the building data, calculation of building heating system power, simulation of heat /cooling demand of the building with "Design Builder" program, calculation of energy piles with "EED" modeling program, Comparison of the system with the basic source of heat, recommendations, conclusions and references, Volume of the thesis 68 p. of the text... [to full text]