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Identifying and locating permeable zones in geothermal fields is a critical step in determining reservoir potential and realizing energy production. Despite a general association with active faults, geothermal systems typically display heterogeneously distributed permeability that makes locating successful wells difficult. Faults are associated with complex distributions of secondary fractures, with variable attitude, fracture density, and connectivity – all of which can influence permeability. Simulations of the local stress state due to slip on a detailed model of the fault system at Brady Geothermal Field, NV, supported by models of key idealized fault geometries, are used to test the relationship between both productive wells or hydrothermal features and failed wells with stress states that promote or suppress fracture. These simulations show that hydrothermal features are generally associated with portions of faults best oriented to slip in the stress state measured at Brady. Critically, regions of enhanced coulomb stress (S_c^((max))) and reduced least compressive principal stress (σ3) that promote fractures occur at narrow, extensional relays and at intersections between faults; at Brady such locations correlate with the locations of production wells and hydrothermal surface manifestations. Despite this positive correlation, several of these structures do not host evidence of hydrothermal flow due to a lack of persistence along the dip of the fault necessary to connect to the heat source at depth. In contrast, regions of reduced S_c^((max)) and enhanced σ3 correspond to volumes that lie near the interior of faults, including at bends and at contractional relays. These locations are generally associated with failed wells; however, major production wells occur at a clear bend in a large fault at Brady. This may reflect the origin of the bend as breached relay and warrants further investigation. / Geology

Basin-hosted stratigraphy in volcanic arc settings reflects the interplay between ancient environments, volcanism, magmatism and tectonism. Lithostratigraphic variations within basins can be used to identify the location and timing of the processes contributing to their evolution. However, when deposits are hydrothermally altered, the use of many traditional analytical techniques for assessing their volcanic origin become impracticable, making analysis challenging. Examination then relies on an integrated mix of detailed macroscopic assessment and techniques utilising remaining stable magmatic phases. The Huka Group at Wairakei-Tauhara Geothermal Field (Wairakei-Tauhara) is primarily comprised of volcanic deposits preserving ~300 kyr of evolution in the Taupo Volcanic Zone (TVZ), New Zealand. Intensive geothermal well drilling in the field has identified the distribution and variation comprising its Waiora and Huka Falls Formations. The volcanic, structural and environmental history of the Huka Group, however, remains poorly understood. This thesis is concerned with identifying the stratigraphic and geothermal significance of the Huka Group from recent drill core samples at Wairakei-Tauhara. Drill core facies analysis confirm a spatially and temporally complex depositional history at the site. Deposits forming Waiora Formation were sourced from local explosive and effusive eruptions over ~100 kyrs within extensional basins hosting paleo-Lake Huka. Lacustrine and fluvial deposition prevailed for the following ~200 kyrs, as volcanism ceased, depositing the Huka Falls Formation. Frequent drilling of Huka Falls Formation has identified and thoroughly constrained facies variations of a local pyroclastic member, the Middle Huka Falls Formation. This eruption evolved as a series of water-supported, eruption-fed density currents from a sublacustrine vent in Tauhara transported beneath Lake Huka. Examined Huka Group core samples were hydrothermally altered and required the use of novel assessment techniques for comprehensive stratigraphic assessment. This alteration provided an opportunity to locally date the geothermal system within the Huka Group reservoir. Stratigraphic variations of resistant magmatic phenocrysts (feldspar) and immobile elements (Ti, Zr, V and Y) added new details of depositional processes and lithostratigraphy. Regional magmatic immobile element comparisons identified geochemical similarities within Huka Group ignimbrites that may have implications for the longevity and recurrence of caldera magma systems in TVZ. Geothermal activity in the Waiora Formation reservoir was dated using pristine hydrothermal adularia and 40Ar/39Ar dating methods. Results recognised a young phase of the system’s evolution (<30 ka) and the applicability of 40Ar/39Ar dating for use in geothermal chronology. Lastly, a conceptual evolutionary model for the Huka Group presents ~300 kyr of depositional processes, landscapes and structural events at Wairakei-Tauhara. The long-lived lacustrine setting is recognised to have been continually modified by episodic volcanism and gradual tectonism. Variations in Huka Group stratigraphy between the Wairakei and Tauhara Fields identify contemporaneous, but separate evolution of the underlying controlling horst (ridge) and graben (basin) structure. This study highlights the unique tectonic, magmatic, volcanic and sedimentary processes forming basins in the TVZ and improve our understanding on the geological evolution of geothermal systems. Techniques trialled in the study are demonstrated to be suitable for investigating altered volcanic materials and can be utilised elsewhere in the TVZ or other geothermal settings.

This research is dedicated to make a foreseeing of the future state of the Kizildere Geothermal Field in order to suggest acceptable solutions to the current problems. The non-isothermal mechanism of the geothermal field is simulated for the pressure and temperature variables. For this purpose, a finite element model (696 four-nodal elements with 750 nodes) of the field is formulated by considering the geological conditions and the present wells already drilled in the area. Then the model is calibrated to the field for the natural state by using appropriate physical properties, boundary and initial conditions. Comparison of the simulated and the observed pressures and temperatures has emphasized a very successful calibration study. After the calibration, response of the field to the production and injection for the period of 1984-2006 has been simulated by applying a history matching study. History matching runs have yielded very good correlations between the observed and the computed values of the pressure and temperature variables. The calibrated and history matched model has been applied to the field to simulate the future performance of the field for different production and injection scenarios. In the first scenario the field is simulated for the next 10-year production period keeping the on-going production conditions. Then, the influence of the production of two new wells has been investigated in two different scenarios. In the forth scenario, the effect of injection from one of the production wells has been simulated.

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.

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

Protective cultivation is widely used nowadays in order to increase crop yield by creating the optimum conditions such as temperature, humidity and CO2 content, irrespective of outside conditions. Since plant production doubles for every 10 degrees increase in temperature to a certain limit, this makes temperature a very important factor for optimum plant growth. In order to keep the greenhouse temperature constant during changes in outside conditions, heating and often cooling are required. Heating of a greenhouse can be done using different systems and design procedures. The applicability of different types of greenhouses is studied at the field local conditions, &Ccedil / avundur-&Ccedil / ankiri, Turkey. Required heating load was calculated that is due to infiltration and conduction through the greenhouse cover at a single design point, which is the minimum outside temperature. Two types of heating systems, soil heating system and bare tube system, were considered. Analysis of results showed that, &Ccedil / avundur geothermal field with 54 &deg / C fluid temperature is suitable for greenhouse heating. Although the existing well &Ccedil / -1 is capable of producing 47 l/s, the flow rate of geothermal fluid for greenhouse heating was limited by 35 l/s due to existing thermal facilities in the area. Among different glazing materials, plastic film covered greenhouses with double poly was found to be the most suitable in terms of heat load calculations. The maximum number of greenhouses (the area of each green house is 216 m2) that can be heated by &Ccedil / avundur Geothermal field was found to be 138 by considering soil heating with double poly glazing material. Annual heat load factor of geothermal energy for greenhouse heating in &Ccedil / avundur area was found to be as high as 96% depending on indoor design temperature and base load.

ABSTRACT CHARACTERIZATION OF KIZILCAHAMAM GEOTHERMAL FIELD BY TRACER TESTING Tevfik Kaya M.S, Petroleum and Natural Gas Engineering Department Supervisor : Assoc. Prof. Dr. Serhat Akin Co-Supervisor : Prof. Dr. Mahmut Parlaktuna September 2005, 107 Pages Kizilcahamam Geothermal Field which is 70 km far from Ankara, has been utilized for Geothermal District Heating System, 25 MWt, 2500 residences capacity, greenhouses heating, thermal facilities since 1994. The average production rate is 350m3/h during the heating season , 150m3/h during the summer season for hot water and yearly average reinjection rate is 114m3/h from the field. The long term projections has been studied concerning on expected pressure decline by matching 10 years field history data which contain dynamic level and temperature data. The pressure decline is 140 kPa in the field between 1999 and 2005 with the existing reinjection rate, if the existing rates do not change, the additional pressure decline which is 120 kPa will be occurred up to 2011. In order to get more information from the field, the fluorescein as tracer has been injected in to the MTA-1, and the samples were collected from the MTA-2, Fethi Bey, IHL-1 and IHL-3 for 3 months. The fluorescein concentration has been detected by using fluorimeter, and tracer concentration time plots were analyzed. The fluoreiscein was detected in short breakthrough time in MTA-2 and Fethi Bey which are close to reinjection well, breakthrough time is longer in IHL-1 and IHL-3. The interpretation of tracer test shows that there is communication between all wells. Tracer concentration time plots were compared with different mathematical models, the best match was obtained with multi-fractured model. These results show that Kizilcahamam field is not homogeneous field. It is expected that increasing the reinjection rate will decrease the pressure decline in the field.

The purpose of this study is to examine the geothermal potential, sustainability, and reinjection possibility of Edremit geothermal field. In order to investigate this, a numerical model consisting of a hot and cold water aquifer system is established. A two dimensional cross sectional model is set to simulate this geothermal system. Different pressure and temperature values are applied to the nodes at the boundaries to perform a steady state calibration which minimizes the computed results and observed values obtained from the near well logs. After the calibration, three alternative scenarios are proposed and the response of the pressure and temperature to these conditions is evaluated. At first the water is pumped from the wells of Yagci, Derman, Entur and ED-3 seperately at a mass rate of 5 kg/s and energy rate of 4.182 x 105 J/s. Then, in scenario 2 the water is pumped at the same rate from all the wells mentioned in the first scenario together. For the third scenario another well is opened to the geothermal system and 80% of the pumped water (temperature being 200C) is injected to the system from the wells while all the wells mentioned are working. The results of these scenarios are utilized to evaluate the reservoir in terms of its response to different production and reinjection conditions. Interpretation of the reservoir response in view of the pressure and temperature declines emphasize that such a simulation study can be applied to assess potential and sustainability of the geothermal systems.