1 2nd European Geothermal PhD Day 2nd of March 2011 Reykjavík, Iceland Collection of Abstracts
3 We are grateful to our sponsors:
5 EUROPEAN GEOTHERMAL PHD DAY 2011 A Message from the President of Iceland Ólafur Ragnar Grímsson It is with great pleasure that I welcome you all to Iceland and congratulate you on your choice of a geothermal future. You are joining a fascinating journey which is laying the foundation for a fundamental global change giving nations all over the world important tools to successfully prevent disastrous climate change. The World Geothermal Congress in Bali last year provided clear evidence of how geothermal utilisation is now advancing. There is already a race on for access to available expertise and equipment. Governments and companies realise that by establishing cooperation with geothermal scientists and engineers, their nations will achieve a competitive advantage in the global economy. The climate crisis constitutes a call for a fundamental energy revolution, a comprehensive transformation from fossil fuel to green energy sources such as geothermal, solar, wind, hydropower and others. In my speech at the Geothermal Forum in New York in February, I analysed the potential for world-wide geothermal progress. The text of my speech is available on the website where a number of my other geothermal speeches can be found. It is my firm belief that geothermal students will have a great future. Your work will lead to discoveries of new knowledge, economic growth and general prosperity for your countries, as well as making the world better and more secure. I congratulate you all and wish you every success in your careers.
6 Dear participants, Welcome to EGPD 2011, the second European Geothermal PhD Day! The first European Geothermal PhD-day was held at the Helmholtz Centre Potzdam in February 2010 and was a great success. Therefore it has been a challenge for the Organizing Committee to plan this event. The PhD-day was an initiative of the EERA joint program in geothermal energy to bring together young scientists working in the field of geothermal energy, and offer them the opportunity to share ideas and build up a network between them. In total around 60 participants from 16 countries will attend the EGPD This collection of abstracts contains the scientific contribution presented at the EGPD 2011 as well as a list of participants. It is also available in electronic format on the EGPD 2011 website, We would like to thank all the participants of the EGPD We are especially grateful to our keynote speakers and the members of the scientific committee for their contribution. Special thanks go to GEORG-geothermal research group, our key-sponsor, for their generous support. We would also like to thank Reykjavík University for providing outstanding facilities for the event. Finally we would like to thank our sponsors: Turboden, GPC-IP, ÍSOR-Iceland Geosurvey, Efla, Verkís, Mannvit, Landsvirkjun, Orkustofnun National Energy Authority, UNU-Geothermal Training Program, Rio Tinto Alcan and 66 North. We hope you enjoy EGPD 2011, The EGPD 2011 organizing committee, Sveinborg Hlíf Gunnarsdóttir Sandra Ósk Snæbjörnsdóttir Steinþór Níelsson María Sigríður Guðjónsdóttir Helga Margrét Helgadóttir Snorri Guðbrandsson Ásgerður Kr. Sigurðardóttir Helgi Arnar Alfreðsson
7 Program Tuesday 1st of March Icebreaker at Orkugarður, Grensásvegur 9 17:30 Registration opens 18:00 Welcoming speech: Guðni Jóhannesson, Director General of the National Energy Authority 18:30 History of Geothermal Utilization in Iceland: Stefán Pálsson 19:00 Introduction from companies and institution that support the event: Ingvar Birgir Friðleifsson, Director of the UNU-GTP Olga Borozdina, Engineer at GPC in France Sigurður H. Markússon, Geologist at Efla Carine Chatenay, Civil engineer at Verkís Peter Danielsen, Geologist at Iceland Geosurvey shows participants well testing equipment. 19:30 Welcoming drinks and snacks Wednesday 2nd of March PhD Day at Reykjavík University, Nauthólsvík 8:15-09:00 Registration and posters up 9:00-9:15 Opening session: Ólafur G. Flóvenz, General Director at Iceland GeoSurvey, head of the scientific committee. Ari Kristinn Jónsson, Rector of Reykjavík University. 09:15-9:45 Keynote lecture: Kristín Vala Ragnarsdóttir, Dean of School of Engineering and Natural Sciences, University of Iceland 9:45-10:30 Short Presentations: Group 1
8 10:30-11:00 Coffee Break 11:00-12:00 Short Presentations: Group 2 12:00-13:00 Short Presentations: Group 3 13:00-13:45 Lunch 13:45-14:15 Keynote lecture: Guðmundur Ómar Friðleifsson, Project manager and coordinator of the Iceland Deep Drilling Project (IDDP) 14:15-15:00 Short Presentations: Group 4 15:00-17:00 Poster Session, coffee & tea 17:00-17:45 Concluding remarks, Poster Awards and Closing Session: Fausto Batini, Coordinator of EERA Joint Program on Geothermal Energy 17:45-21:00 Party for participants Scientific Committee Ólafur G. Flóvenz, General director at ISOR, IcelandGeosurvey Einar Gunnlaugsson, Manager of Geothermal Research at Reykjavik Energy Guðrún Arnbjörg Sævarsdóttir, Assistant Professor and Department Head, School of Science and Engineering, Reykjavík University Fausto Batini, Coordinator of EERA Joint Program on Geothermal Energy Jan-Diederik van Wees, TNO, Business Unit Geo-Energy and Geo-Information, Utrecht
9 Participants First Name Last Name Institution / Facility 1 Edda Sif Aradóttir University of Iceland and Reykjavík Energy 2 Márton Barcza University of Szeged (Hungary) 3 Thomas Benson Stanford University/Massachusetts Institute of Technology 4 Björn Bjartmarsson School for Renwable Energy and Dept. Of Mechanical and Industrial Engineering, University of Iceland, 5 Héðinn Björnsson University of Iceland/Iceland Geosurvey 6 Damien Bonté Vrije Universiteit Amsterdam, FALW, Tectonic group 7 Olga Borozdina GPC Instrumentation Process (GPC IP) 8 Maren Brehme Helmholtz Centre Potsdam - German Research Centre for Geosciences (GFZ), International Centre for Geothermal Research 9 José Estévez University of Iceland / UNU-GTP 10 Sara Focaccia DICAM- University of Bologna 11 Laura Foulquier GPC Instrumentation Process (GPC IP) 12 Henning Francke GFZ Potsdam 13 Iwona Galeczka University of Iceland / Institute of Earth Sciences 14 Iska Gedzius Insitute of Peroleum Engineering (Clausthal University of Technology) 15 Snorri Guðbrandsson University of Iceland / Institute of Earth Sciences 16 Maria Gudjonsdottir Reykjavik University / School of Science and Engineering 17 Egill Árni Guðnason ÍSOR / University of Iceland 18 Sveinborg Gunnarsdóttir University of Iceland / ISOR Hlíf 19 Helga Helgadóttir ÍSOR/University of Iceland Margrét 20 Heimir Hjartarson Faculty of Industrial Engineering, Mechanical Engineering and Computer Science 21 Henrik Holmberg Dept of Energy and Process Engineering, NTNU 22 Saqib Javed Building Services Engineering, Chalmers University of Technology 23 Hanna Kaasalainen University of Iceland/Nordic Volcanological Center 24 Marta Rós Karlsdóttir University of Iceland / Department of Industrial Engineering, Mechanical Engineering and Computer Sciences 25 Evgenia Kontoleontos National Technical University of Athens /School of Mechanical Engineering 26 Éva Kun Szeged University 27 Heiko Liebel Norwegian University of Science and Technology 28 Magnus Løberg University of Bergen Bjørnsen 29 Mary Luchko Moscow State University 30 Kiflom G. Mesfin University of Iceland / Institute of Earth Sciences 31 Helena Nakos Chalmers University of Technology
10 32 Steinþór Níelsson University of Iceland / Iceland GeoSurvey 33 Mochamad Nukman GFZ - Potsdam 34 Yodha Yudhistra Nusiaputra IKET, Karlsruhe Institute of Technology (KIT) 35 Pacifica F. Ogola UNUGTP / University of Iceland Achieng 36 Auður Agla Óladóttir ÍSOR, Háskóli íslands 37 Snjolaug Olafsdottir University of Iceland, Faculty of Civil and Environmental Engineering 38 Jonas Olsson University of Iceland / Institute of Earth Sciences 39 Kevin Padilla Faculty of Earth Sciences, University of Iceland 40 Marco Pola Dipartimento di Geoscienze Università degli Studi di Padova 41 Thomas Reinsch Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences 42 Dorothea Reyer Geoscience Centre, University of Göttingen 43 Alejandro Rodríguez University of Iceland / Institute of Earth Sciences 44 Guðni Karl Rosenkjær University of British Columbia/Iceland Geosurvey 45 Uwera Rutagarama University of Iceland/United Nations Geothermal Training program 46 Sanaz Saeid Technical university of Delft 47 Matias Sanchez Schneider Royal Holloway, University of London 48 Tor Harald Sandve Department of Mathematics, University of Bergen 49 Samuel Scott Reykjavik Energy Graduate School of Sustainable Systems (REYST), University of Iceland 50 Haffen Sébastien EOST University of Strasbourg 51 Ásgerður Sigurðardóttir University of Iceland / Institute of Kristrún Earth Sciences 52 Gunnar Skúlason Kaldal University of Iceland 53 Sandra Snaebjornsdottir University of Iceland / Iceland GeoSurvey 54 Christopher Steins RWTH Aachen University, Institute of Heat and Mass Transfer 55 Marco Stringari University of Torino (Italy) 56 Christian Vetter Karlsruhe Insitute of Technology (KIT) 57 Esther Vogt Leibniz-Intitut for Applied Geophysics 58 LiWah Wong GFZ German Research Centre for Geosciences
12 Reactive transport models for mineral CO 2 sequestration in basaltic rocks Edda S.P. Aradottir 1,2,*, Eric Sonnenthal 3, Grimur Bjornsson 4, Hannes Jonsson 1 1 Science Institute of the University of Iceland, VR-III, 107 Reykjavik, Iceland 2 Reykjavik Energy, Baejarhalsi 1, IS-110, Reykjavik, Iceland 3 Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley CA 94720, USA 4 Reykjavik Geothermal, Kollunarklettsvegi 1, IS-104, Reykjavik, Iceland * Educational level: Ph.D. Reacting CO 2 with basalt to form thermodynamically stable carbon-rich minerals may provide a long lasting, thermodynamically stable and environmentally benign solution to reduce anthropogenic CO 2 emissions. We present here development of reactive transport models of this process with focus on the CarbFix experiment at Hellisheidi geothermal power plant in Iceland. There, up to 2.2 tons/year of purified CO 2 of volcanic origin will be dissolved in water and injected at intermediate depths ( m) into relatively fresh basaltic lavas. Plans call for a full-scale injection if the experiment is successful. Reactive transport modeling is an important factor in the CarbFix project, providing tools to predict and optimize long-term management of the injection site as well as to quantify the amount of CO 2 that has the potential of being mineralized. TOUGHREACT and itough2 are used to develop reactive fluid flow models that simulate hydrology and mineral alteration associated with injecting dissolved CO 2 into basalts. Natural analogs of CO 2 -water-basalt interactions provide important insight into the secondary mineralogy associated with the CarbFix CO 2 injection, and hence which minerals are likely to compete with carbonates for dissolved cations. Secondary minerals of CO 2 rich and depleted water basalt interactions have been studied with the objective of defining alteration minerals likely to form in the CarbFix injection. Based on this work, the mineral reactions database in TOUGHREACT was revised and extended, providing an internally consistent database suitable for mineral reactions of interest for this study. Our main focus has been on developing a three dimensional field model of the injection site at Hellisheidi. Hydrological parameters of the model were calibrated using itough2 to simulate tracer tests that have been ongoing since Modeling results indicate groundwater velocity in the reservoir to be significantly lower than expected. The slow groundwater velocity may necessitate increasing groundwater flow by producing downstream wells at low rates after CO 2 injection has started. The three dimensional numerical model has proven to be a valuable tool in simulating different injection and pumping schemes. Reactive chemistry was coupled to the model and TOUGHREACT used for reactive transport simulations, which are ongoing. Preliminary results confirm dissolution of primary basaltic minerals as well as carbonate precipitation. Secondary mineral abundance is highly dependent on temperature, pco 2 and flow rate. Optimally, simulations with the CarbFix field model should determine which injection scenario will maximize mineralization of injected CO 2 as well as to show the depth and temperature range best suited for the mineralization.
13 Changes of the states of geothermal wells according to the geophysical research in the south-eastern area of Hungary Márton Barcza 1 András Bálint 1 János Szanyi, PhD 1 Khomine Allow 1 Sándor Kiss 1 Tibor Jánosi Mózes 1 1 Department of Mineralogy Geochemistry and Petrology, University of Szeged, Hungary PhD Student keywords: geophysics, geothermal energy, well logging, reinjection Abstract The geothermal field is known from the 1950 s, as a result of abortive CH-exploration. The drastic decrease of the hydraulic head and the wastewater disposal into the surface water causes environmental problems. Actually the wells and their mutual effects are being examined completely. The poster presents the circumstances of the examinations and the results which are produced so far. In the south-eastern area of Hungary we are investigating where and under what exploitation and technological circumstances it is justified to reinject thermal water so that the exploited water can be refilled and the exploitation can be planned and maintainable on a long term. Several research tasks are being realized at the same time. Actually the major part of the research of well logging has been realized and the research of well interference and tests of reinjection and its technological elaboration are in progress. Within the project we realize several kinds of research, on the one hand, complete research is being realized of all the 20 geothermal wells in the area, on the other hand, the mutual interference is being examined among the wells, and we also perform permanent pressure tests to study the territorial effects. The complete research of the wells means the examination of the structure of the wells (well bottom, casing, place and locking of insulation, place of active filters etc.) Since this kind of research has never been carried out before. Moreover, dynamic parameter of the wells can be controlled: determination of the flow profile, determination of the transfer in the static well, and the determination of the well hydraulic parameters. During the last research we realize continuous measurement of flow and temperature and also measurement of pressure in the depth and on the surface.
14 Figure 1 Filtered and active segments of the wells and accretions It can be observed in a flowing well in what proportion the filters contribute to the yield of the well. By changing gradually the yield of the well the hydraulic parameters of the opened aquifer can be determined. according to the research carried out so far the technical state of the wells are quite different, in several cases the bottom of the well could not be reached, since the lower insulation cannot be crossed (probably an unidentified object had fallen into the well) as can be seen in Figure 1. We have presented the certain filter segments at the original well drilling by purple, the active segments by green and the accretion calculated from the depth of the original well bottom is presented by grey. In the south-eastern area there has been an intensive thermal water production from the 1950 s. Instead of the emplacement on the surface of the waste water, the reinjection of the cooled water would be necessary. Actually the examination of the state of these wells are in progress by geophysical methods, therefore the data gained in this way give us a possibility to realize the hydrodynamic and transport model of the area and the planning of the reinjection.
15 Temperature Characterization of the Cove Fort-Sulphurdale Geothermal Field Thomas Benson, M. Nafi Toksöz and Haijiang Zhang Department of Earth, Atmospheric and Planetary Sciences Massachusetts Institute of Technology Cambridge, MA, 02139, United States ABSTRACT: The Cove Fort-Sulphurdale geothermal field is located in the transition zone between the Basin and Range Province and the Colorado Plateau. Though this region has a complex geologic history, it has very high surface heat flow and extensive normal faulting, making it favorable towards geothermal energy extraction. To examine its potential, a wide variety of geophysical data are explored. All data indicate that underneath Cove Fort, there is an anomalous region whose physical properties indicate the presence of a large, vast geothermal reservoir. Using these data, specifically seismic velocities, we calculate reservoir temperatures and compare the results with measured surface data. The results show that the hot body is on average 150 C C hotter than the surrounding rocks. This method, if backed up with detailed laboratory and structural data, could prove to be a useful method for standardizing the evaluation of geothermal reservoirs.
16 Constraining Reservoir Models with Surface Measurements Héðinn Björnsson 1 1 Natural Science, University of Iceland, Iceland (PhD student) Conventional reservoir models are primarily constrained by well measurements of temperature, pressure and production. As wells tend to be in a small part of the geothermal system, this approach leaves large parts of the model largely unconstrained, which can become problematic especially for longer term predictions and when trying to predict the properties of new wells. Geophysical surface measurements of parameters connected to geothermal exploitation can help to constrain these outer parts of the model if included in the inversion process. Such measurements include TEM and MT measurements of resistivity which is strongly connected to temperature anomalies as well as measurements of gravity and subduction which is connected to the pressure drawdown caused by the exploitation of the geothermal system. The geothermal system that has been the focus of this study is the Reykjanes geothermal field in south east Iceland. The field was taken into large scale production in 2006 in one step from producing about 40 kg/s to producing 800 kg/s causing a 40 bar pressure drawdown and significant changes in the gravity signal of the area. Preliminary results of modelling the gravity response connected to the drawdown calculated for the TOUGH2 model of the Reykjanes geothermal field indicate that gravity measurements are not sufficiently explained by the calculated drawdown. Further study will be needed to see if this means that the gravity measurements can be used to further constrain the model. New MT measurements of the Reykjanes geothermal field have been made and they are being processed. It will be of great interest to see how these measurements correspond to the current model of the field.
17 A LUMPED PARAMETER MODELLING METHOD FOR HIGH- TEMPERATURE GEOTHERMAL RESERVOIRS Björn Bjartmarsson1,2 1School for Renwable Energy and Dept. Of Mechanical and Industrial Engineering, University of Iceland, Iceland. 2Currently at EFLA Consulting Engineers, Ltd. Reykjavik, Icealnd. High-temperature geothermal resources, which are those that are exploited for producing electricity, have been thoroughly studied using a variety of techniques. They have been modeled conceptually and numerically, using programs such as itough2. There has not been much effort placed on using more simple techniques, such as lumped parameter methods. This is due to the necessity of dealing with temperature effects, and up to date, lumped parameter methods have been mostly limited to models incorporating only pressure changes. Here a method has been developed which accommodates both pressure and temperature/enthalpy data. A one and two-tank model has been elaborated. This model has been developed in MATLAB and utilizes the LSQNONLIN and ODE23T algorithms which are in the software library. The model has been tested against user generated data as well as data from Krafla and Bjarnarflag geothermal power stations. The model was found to have a close fit to the data in some cases, with the 1-tank model matching the data more closely. The results show the possibility of using the model as a part of the management of high temperature geothermal reservoirs. Figure 1 illustrates the effectiveness of the model in matching user generated data. The root mean square (RMS) value, representing the quality of fit of the model for this is The 1-tank model obtained a better fit in all cases. In figure 2, the quality of the fit of the model to actual data from Bjarnarflag, Iceland is shown. The RMS value is , which is much higher than that for the the user generated data, but follows the longer term trends in the parameters. Further work is necessary to obtain a better fit with the 2-tank model and the model has not yet been used to predict response to varying future mass flow scenarios. It was also noted that the measurement of the parameters was not done very frequently, which reduced the data set size and potential accuracy of the model as a result. In addition, seasonal fluctuations are not seen. New measurement technology called tracer flow testing (TFT) allows for measurement of parameters without the need to take wells off-line, presenting the possibility of more frequent measurements.
18 Figure 1: User generated data, 1-tank model with +/- 5% random noise Figure 2: Bjarnarflag well BJ-11 simulated with a 1-tank model
19 New temperatures for the Paris Basin Results from tectonic-heat Flow modelling Damien Bonté 1, Jan Diederik Van Wees 1-2, Laurent Guillou-Frottier 3, Vincent Bouchot 3, Olivier Serrano 3 1. Vrije Universiteit, de Boelelaan 1085, 1081 HV Amsterdam, The Netherlands; 2. TNO, Geo-Energy, Princetonlaan 6, Postbus 80015, 3508 TA Utrecht, The Netherlands 3. BRGM, 3 avenue Claude Guillemin, BP 6009, Orléans cedex 2, France Following the work on the temperature in the French sedimentary basins, published in Bonté et al (2010), the objective of this work is a more precise determination and better understanding of presentday temperature in the Paris Basin. For this purpose, we use a modelling approach which takes into account: 1- the transient effects of the temperature and 2- the basin layering and the related petrophysical parameters. The frame of this work is a collaboration between the TNO (geological survey of the Netherlands) and the BRGM (French geological survey). Located on the inner part of the Variscan Orogen, the Paris Basin has evolved from the Permian as an intracratonic basin. The tectonic evolution of the basin through time has a strong influence on the temperature, essentially because of the transient effect on the temperature. The modelling approach we use takes into account the sedimentation and the tectonic events from the Permian to Present-day. During this period of 250 Ma, the Paris Basin has experienced several events which have influenced the sedimentation or at the opposite, generated some erosion (e.g. the opening of the Ligurian Tethys during the Lias and a NW-SE small wavelength compressive phase from the Berriasian to the Late Aptian in relation with the opening of the Bay of Biscay - Guillocheau et al, 2000). The most important event for the present-day temperature in the Paris Basin is the Miocene uplift of the Vosges- Black Forest (Ziegler, 1990). As the impact of a tectonic event at the lithospheric scale on the temperature is considered to last 20 Ma, this Miocene tectonic event has still repercussions on the present day temperature we are trying to precisely determine. Using the multi-1d probabilistic tectonic heat flow modelling approach described in Van Wees et al (2009), together with novel 3D modelling mechanisms, we constrain the present-day temperature in the Paris Basin. For this modelling, we take into account the geometry of the layering and the petrophysical parameters (i.e., thermal conductivity, the radiogenic heat production of the sedimentary layers in relation with their facies and the radiogenic heat production of the basement).
20 The results of our modelling are verified using two sets of data; for the past events the heat flow is calibrated with Vitrinite Reflectance measurements and for the present day temperature using BHT s (Bottom Hole Temperature) and DST s (Drill Stem Test). As a result of this modelling, we are able to present present-day temperature on any required layer within the basin. The result we present is a new precise map temperature at the basement layer. Bonté D., Guillou-Frottier L., Garibaldi C., Bourgine B., Lopez S., Bouchot V. & Lucazeau F., Subsurface temperature maps in French sedimentary basins: new data compilation and interpolation. Bulletin de la Société Géologique de France, 181, Guillocheau F., Robin C., Allemand P., Bourquin S., Brault N., Dromart G., Friedenberg R., Garcia J.P., Gaulier J.M., Gaumet F. & al., Meso-Cenozoic geodynamic evolution of the Paris Basin: 3D stratigraphic constraints. Geodinamica Acta, 13, Van Wees J.D., Van Bergen F., David P., Nepveu M., Beekman F., Cloetingh S. & Bonté D., Probabilistic tectonic heat flow modeling for basin maturation: Assessment method and applications. Marine and Petroleum Geology, 26, Ziegler P.A., 1990, Geological atlas of Western and Central Europe (2nd ed.). Shell Internationale Petroleum Maatschappij B.V, Geological Society of London, Elsevier, Amsterdam, 239 p.
21 The integrated view on a geothermal reservoir Maren Brehme 1, Muhamad Andhika 1,2, Günter Zimmermann 1, Simona Regenspurg 1 1 Helmholtz Centre Potsdam - German Research Centre for Geosciences (GFZ), International Centre for Geothermal Research, Telegrafenberg, Potsdam, Germany 2 Pertamina Geothermal Energy, Skyline Building, MH. Thamrin No.9, Jakarta 10340, Indonesia PhD As Indonesia with its many islands is located at the ring of fire it represents a very good environment for geothermal energy utilization. Indonesian geothermal sites are mostly high enthalpy fields located often close to volcanoes. The total potential of geothermal areas in Indonesia is estimated to be 27 GW e. However, due to site-specific geologic conditions each geothermal site deals with certain problems such as various types of scaling, acid water, or rapid cooling of the reservoir. In this work, available hydraulical, geological, and hydrochemical properties of an operated Indonesian geothermal location were reviewed. Additionally, water samples of wells and hot springs were taken. The physicochemical parameters ph, electrical conductivity, redox potential, temperature as well as HCO 3 -concentration were measured in-situ. The samples taken were then analysed for major ions at GFZ laboratories. At the location investigated, three reservoirs with different fluid composition, located at different depths provide the steam for electricity production. One reservoir is represented by medium to high Si- and Cl-concentrations (350 and 440 mg/l). One other reservoir shows extremely high SO 4 - and Cl-concentrations (1600 and 1500 mg/l). Beside the ions the ph value is typical for every reservoir. The water of one reservoir is characterized by extremely acid water with a ph of 1.1. All sample values were plotted in a Giggenbach-diagram. As they have low or no HCO 3 -concentrations the samples plot on the line between Cl and SO 4 and the source is assessed to be acid or neutral chloride water. In order to understand subsurface water pathways and the connection between the reservoirs a thermal-hydraulic model will be generated during my PhD work. Additionally, the development of a hydrochemical transport model will be employed to help explain watermixing processes. These models and the gathered information about geology, geological structures, hydraulic information, water and rock chemistry will lead to an integrated view on this geothermal site.
22 References: DARMA S., POERNOMO A., PRAMONO A., BRAHMANTIO E.A., KAMAH Y., SUHERMANTO G., 2010: The Role of Pertamina Geothermal Energy (PGE) in Completing Geothermal Power Plants Achieving 10,000 MW in Indonesia, Proceedings World Geothermal Congress 2010 Bali, Indonesia GIGGENBACH, W.F., 1988: Geothermal solute equilibria. Derivation of Na-K-Mg-Ca geoindicators. Geochim. Cosmochim. Acta, 52,
23 Geostatistical modeling of natural mean s properties for flux simulation through FEM,FDM codes: analysis of Thermal Response Test data Sara Focaccia 1, Roberto Bruno 2, Francesco Tinti 2 1,2 DICAM- University of Bologna, Italy PhD student Thermal Response Test (TRT) is an onsite test used to characterize the thermal properties of shallow underground and of the borehole used to extract / inject heat. The consolidated deterministic methodology based on the Infinite Linear Source (ILS) theory is reviewed and a nested probabilistic approach for TRT output interpretation is proposed. 5 key parameters are required for applying the theory and must be deduced by the test records. Fig.1- Thermal Response Test rig 3 of them are the target (ground thermal conductivityand borehole thermal resistance-r b ), 2 of them (initial time-t i and final time-t f ) are necessary for applying the classical computing procedure based on a linear regression and guess values. The probabilistic approach calls for a nested sequential procedure. Based on a geostatistical residual model in the time-logarithm, the drift analysis of temperature records allows for robust ground thermal conductivity ( ) identification. The modeling of log-time residual variogram allows for the computation of the estimation variance for different regression conditions. Consequently, the initial time is defined as the time at which the ILS theory hypothesis is not verified by the TRT results and the final time is simply identified, in advance and during the test, by the minimum time able to guarantee the required confidence for the regression analysis results. Afterwards, based on i and t f estimates, a new monovariate regression on the original data allows for the identification of the theoretical R b. Then, the methodology requires the user to propose a guess probability distribution function for both variables. Once available, the identification of
24 - Validity area of R b - b equation Fig. 2 -R b relationship is found. And finally the conditional expectation allows for identifying the correct and optimal couple of the -R b estimated values.
25 Two-phase flow in the brine circuit of a geothermal plant Hennin Francke Helmholtz-Zentrum Potsdam, Deutsches GeoForschungsZentrum - GFZ Telegrafenberg, D Potsdam graduate engineer With two boreholes successfully drilled and their sufficient productivity proven, geothermal energy can be exploited basically by extracting hot brine from a deep reservoir using an electrical submersible pump (ESP) in one borehole and reinjecting it into the other one after extracting heat in a heat exchanger. The brine extracted usually contains considerable amounts of dissolved salts (e.g. NaCl, CaCl) and gases (e. g. N 2, CH 4, CO 2 ). Due to the large pressure difference between aquifer and the above ground facility (hydrostatic + friction), degassing and/or evaporation can occur during production with all its consequences: The degassing of small amounts of gas increases the volume gas fraction considerably. The gas fraction influences density, viscosity, heat conductivity of the resulting two-phase medium. Density reduction at constant mass flow increases the fluid s mean velocity, causing an increased wall friction. Thus, it can significantly affect the performance of the connected devices (pump, heat exchanger etc.). Furthermore in the case of degassing of CO 2, the ph rises, which can lead to precipitation of solids. In order to avoid this, the pressure should be kept above a certain value in the whole brine circuit. For designing and dimensioning of the brine circuit a hydraulic model is needed. It must be capable of reproducing the physical properties of the brine in a two phase flow including the degassing process. Such a model would allow for a prediction of the ESP's pressure head required to maintain a given pressure level at the well head. That way the ESP s power consumption can be estimated, which is usually crucial for the economic performance of the whole geothermic power plant. As there are no specific property functions for brines, being a mixture of varying composition, the fluid s properties have to be calculated using correlations for two-phase media and property functions from the literature for density, specific enthalpy and solubility for aqueous solutions of chlorides and nitrogen as well as carbon dioxide. We present a numerical model of the production well. It has been implemented in Modelica (modeling language) using the developing environment DYMOLA. The well model accounts for degassing, evaporation, heat conduction through the pipe wall and pressure losses through two-phase friction. It also features a fluid property model for the two-phase brine, which can
26 be adapted to specific compositions. The well is discretized and balances of mass, momentum and energy are calculated for each segment. In order to decrease numerical effort while still having a resolution fine enough where needed, an automatic step size adaptation has been developed.
27 Experimental studies on CO 2 sequestration in basaltic rocks with the plug flow reactor Iwona Galeczka* Domenik Wolff-Boenisch Sigurdur Gislason Institute of Earth Science, University of Iceland, Askja, Sturlugata 7, 101 Reykjavik, Iceland Mineral trapping in silicate rocks is considered as the most stable strategy of CO 2 storage. Conceptual model of CO 2 mineral fixation in Iceland (CarbFix.com) assumes that acidic carbonated waters injected into basaltic rocks will initially cause rock dissolution and release of divalent cations such as Ca 2+, Mg 2+ and Fe 2+. As reactions progress, these elements will combine with CO 2-3 and precipitate as carbonates due to increasing ph. Large scale experiment with a plug flow reactor imitating chemical and physical conditions within the basaltic rocks after CO 2 injection, gives an opportunity to study the rate of basaltic material dissolution and solid replacement reactions under controlled CO 2 conditions. The experimental set-up makes it possible to follow changes in ph, Eh and chemical composition of the fluid on different levels along the flow path within the column. Characterization and quantification of secondary minerals (carbonates and clays) enables determination of molar volume and porosity changes with time. Data obtained from experiment will be used in reactive transport models to elucidate the advance of reaction fronts, forecast porosity changes followed by estimation of upper limit CO 2 injected into a given geological formation. Experimental set-up consists of 7 titanium compartments assembled into a 2.5 m long tube, with 5.4 cm outer diameter and 5 cm inner diameter, corresponding to a volume of ~ 5 dm 3. The column will be filled up with basaltic glass grains, 45 to100 µm in size, of known chemical composition and surface characteristic. CO 2 saturated water will be pumped under 75 bar pressure through the column. 8 port multi-positon stream selector connected to each compartment of the column enables sampling a solute at a chosen level of flow path. During sampling, outlet solution flows through a sampling loop of known volume, followed by ph, Eh electrodes. Expander connected to the sampling loop makes it possible to measure changes in CO 2 concentration. After approximately one year of experiment duration, samples of solid material will be taken from all intervals of the plug and examined by SEM- EDS, TEM, XRD and μsimct. *
28 Optimum geothermal well constructions to maximize the heat output and minimize costs Ms. Dipl.-Ing. Iska Gedzius 1, Dr. Dr.-Ing. C. Teodoriu 1, Prof. Dr.-Ing. K. M. Reinicke 1 1 Adress of authors: Institute of Petroleum Engineering, Agricolastraße 10, Clausthal-Zellerfeld, Clausthal University of Technology, Germany contact of the summer school participant for future correspondence: Educational level (Dipl.-Ing., PhD-Student) Introduction: Economics require the extraction of deep geothermal energy at high rates and temperatures and low costs for the construction and operation of the necessary systems. For average geothermal temperature gradients, i.e. 3 ºC per 100 meter, wells of m and more must be drilled with end diameters of 7 inch and more to access high temperatures and minimize frictional pressure in the well. At this depth, formations typically need to be stimulated to achieve the necessary high inflows into the well. Formation brines encountered at sub salt levels in Germany are fully saturated with salts. Their corrosivity and scaling tendency requires special attention. Well costs for deep natural gas wells in Germany average approximately 2.5 Million Euro per m which is too high to achieve satisfactory economics for two- and three-well geothermal systems in use to date. Work is ongoing at the Institute of Petroleum Engineering (ITE) to identify and evaluate enhanced geothermal systems on the basis of latest horizontal/multilateral drilling and stimulation technology. This work is part of a larger cooperative research initiative called GEBO: Geothermal Energy and High-Performance Drilling. This paper presents two one well concepts targeting at minimizing drilling cost and at maximizing energy output. One-Well-Concept - Open System: In an open system, the carrier fluid for the geothermal energy is in contact with the rock of the geothermal reservoir. The GenesSys concept in Germany was to slant a well through the target formations in a direction, to enable the creation of a (vertical) fracture in a plane perpendicular to the direction of the slant. The fracture was to connect to an overlying (porous and permeable) formation. In operation, fluid would be circulated down the well, through the fracture to the overlying formation and through this formation back to the well. To be successful, the concept requires knowledge of the state of stress and in the formations to be fraced and permeability in the formation part of circulation system. the An open system, independent of permeability and porosity, can be generated by drilling two or more horizontal laterals of sufficient length above (Figure 1) or next to each other and to connect the laterals by (vertical) fractures. Fractures will open in a direction perpendicular to the least principal stress. Under normal conditions is a horizontal stress, which is typically dependent on direction, usually the result of acting tectonics stresses. To be successful, the concept requires that the state of stress in the formations targeted geothermal energy exploitation is known. Figure 1 shows the Figure 1: One-Well-Concept as an open system this for
29 concept with two horizontal laterals and the heat exchangers with the fracs being generated from the upper lateral. In operation, cold water (in blue) is injected down the well through the tubing, into the lower lateral, passes through the factures, and is produced as hot water (in red) through the upper lateral and produced back to the surface via the annulus. In a first approximation, penny shaped fractures will be created in the fracturing process resulting in an inefficient use of the heat exchanger areas, if only two laterals are employed as in Figure 1. Simulations and economic evaluations will have to be carried out to evaluate the benefit of a third lateral penetrating the fractures close to the top. In this three lateral configuration, cold fluid would be injected into the middle lateral and produced through the upper and lower laterals. The uniform distribution of the injected cold fluid across the created factures requires special attention to avoid hydraulic short circuiting of the injected cold water through the fractures offering the least resistance to flow. One-Well-Concept - Closed System: In a closed system the carrier fluid for the geothermal energy is not in contact with the rock of the geothermal reservoir, but flows inside a cased hole. Closed systems avoid the risks resulting from the hot and highly mineralized reservoir brines. A possible concept for a closed system with better recovery efficiencies than achieved with a normal geothermal probe is shown in Figure 2. For this concept, a well - having reached the target geothermal reservoirs is deviated (from a position above the total depth of the vertical well) out of the vertical and steered in a spiral ending at the bottom of the vertical well again. To avoid excessive loading of the tubular, deviation radii should not lead to excessive loading levels for the tubulars employed. In operation, cold fluid would be pumped down the tubing into the spirally-wound well, and produced back to the surface through the annulus. Challenges of one-well-concepts include: Drilling larger diameter wells because of the counter-current flow all the way down to the reservoir, Steering wells at high temperatures, Providing insulation between the counter-current flow of cold fluid in the tubing and hot fluid in the annulus and for open systems Generation of sustainable heat exchanger, Controlling the distribution of fluids into the fracture systems, Knowing the state of stress in the formations to be fraced. Figure 2: One-Well-Concept as a closed system
30 CO 2 Mineralization into Basaltic Formations at the Hellisheiði Geothermal Field The CarbFix Project Snorri Gudbrandsson 1, Helgi A. Alfredsson 2 and Sigurdur R. Gíslason 3 1 PhD student at the Institute of Earth Sciences, University of Iceland, Askja Sturlugata 7, IS- 101 Reykjavík, Iceland 2 PhD student at the Institute of Earth Sciences, University of Iceland, Askja Sturlugata 7, IS-101 Reykjavík, Iceland 3 Research Professor at the Institute of Earth Sciences, University of Iceland, Askja Sturlugata 7, IS-101 Reykjavík, Iceland The reduction of industrial CO 2 emissions is one of the main challenges of this century. Among commonly proposed CO 2 storage techniques, the injection of anthropogenic CO 2 into deep geologic formations is quite promising. One way to enhance the long-term stability of injected CO 2 is through the formation of carbonate minerals. Carbonate minerals provide a long lasting, thermodynamically stable and environmentally benign carbon storage host. Mineral carbonation of CO 2 could be enhanced by its injection into silicate rocks rich in divalent metal cations such as basalts and ultra-mafic rocks. Hellisheiði Powerplant is located at Hellisheiði geothermal field, which is of basaltic composition, crystalline basalt as well as basaltic glass. The CarbFix project aims to inject the CO 2 emitted from the power plant, into the basaltic formation on site. This process involves full carbonation of local groundwater during the injection. The project aims to develop a practical and cost-effective technology for in-situ carbonation and later mineralization in basalts. CarbFix is a combined program consisting of field scale injection of CO 2 charged waters into basaltic rocks, laboratory based experiments, study of natural CO 2 waters as natural analogue and state of the art geochemical modelling. The program is a joint venture between Reykjavik Energy, University of Iceland, The Earth Institute at Columbia University in New York, and the CNRS, Université Paul Sabatier in France, as well as other external funding.
31 Properties of Two Phase Flow of Water and Steam in Geothermal Reservoirs Maria Gudjonsdottir 1, Jonas Eliasson 2, Halldor Palsson 3, Gudrun Saevarsdottir 4 1 Ph.D. Candidate, School of Science and Engineering, Reykjavik University, Menntavegur 1, 101 Reykjavik Iceland 2 Prof. Emeritus, Faculty of Civil and Environmental Sciences, VRII, Hjardarhagi 2-6, 107 Reykjavík, Iceland 3 Assoc. Professor, Faculty of Industrial-, Mechanical Engineering and Computer Science, VRII, Hjardarhagi 2-6, 107 Reykjavík, Iceland 4 Assistant Professor, School of Science and Engineering, Reykjavik University Menntavegur 1, 101 Reykjavik Iceland Abstract A basic understanding of two phase flow of water and steam in geothermal reservoirs is essential to predict the performance of high temperature geothermal wells and reservoirs. Current simulation tools for liquid dominated reservoirs base flow calculations on the traditional Darcy equation, where flow is a function of fluid parameters such as density and viscosity, as well as the intrinsic permeability of the surrounding media to transmit fluid. For two phase flow of water and steam, this approach is based on the relative permeability of each phase, which is the effective portion of the intrinsic permeability for the phase. The traditional flow relation neglects interfacial shear forces and buoyancy effects acting between the two phases, introducing errors unless the two phases are flowing in completely separated channels. Thus, this formulation predicts that relative permeability is linearly dependant on the water saturation, since it should only account for the portion occupied by that phase in the cross sectional area of the flow channel. Experiments, generally with one dimensional flow, have shown this not to be the case, indicating that the relative permeability scales with the water saturation with an exponent greater than one (Eliasson et al. 1980, Verma 1986, Piquemal 1994, Satik 1998, Mahiya 1999). Many of the past measurements of relative permeabilities of water and steam have in common that they have been performed under horizontal flow conditions and do show deviation from the linear dependency on water saturation, contrary to the expected results from theory. Furthermore, results from measurements in a vertical setup show that the two phase fluid can flow upwards although pressure gradient is lower than the hydrostatic force which contradicts the behavior suggested by theory (Eliasson et al. 1980).
32 It is of great importance to perform further measurements in this field, especially for a flow in a vertical setup. This Ph.D. work is a collaboration project between the University of Iceland and Reykjavik University where relative permeabilities will be measured in a large scale experiment. The results will be used to develop new empirical relationships for two phase flow in geothermal reservoirs and will also be used to improve current simulation tools and used in the construction of a new reservoir modeling tool under development in a connected project. The goal of the experimental work is to develop empirical relationships for two phase flow, using relative permeabilities, which describes the flow more accurately than existing formulations do. References Eliasson, J, S.P. Kjaran, G. Gunnarsson, Two phase flow in porous media and the concept of relative permeabilities. Proc. 6 th Workshop on Geothermal Reservoir Engineering Dec , 1980 Stanford Geothermal Program. Mahiya, G.F Experimental Measurement of Steam-Water Relative Permeability. M.Sc. Thesis, Stanford University, Stanford. CA. Piquemal, J Saturated Steam Relative Permeabilities of Unconsolidated Porous Media. Transport in Porous Media, Vol. 17, pp Satik, C A Measurement of Steam-Water Relative Permeability. Proceedings. Twenty-Third Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA. Verma, A.K Effects of Phase Transformation of Steam-Water Relative Permeabilities. Earth Sciences Division Lawrence Berkeley Laboratory. University of California Berkeley, CA.
33 The GEISER project Egill Árni Guðnason 1 Mr. Kristján Ágústsson, Dr. Ólafur G. Flóvenz 2 1 University of Iceland / Iceland Geosurvey, Geophysics, Iceland 2 Iceland Geosurvey, Iceland Educational level : MSc The GEISER (Geothermal Engineering Integrating of Induced Seismicity in Reservoirs) project started at the beginning of the year 2010, and is funded by the European Commission. The project will address several of the major challenges the development of geothermal energy is facing, including the mitigation of induced seismicity to an acceptable level. The specific goals of GEISER are: to understand why seismicity is induced in some cases but not others to assess the probability of seismic hazards depending on geological setting and geographical location to propose licensing and monitoring guidelines for local authorities, including a definition acceptable ground motion levels to investigate strategies for 'soft stimulation' that sufficiently improve the geothermal reservoir's hydraulic properties without producing earthquakes that could be felt or cause damage To address these objectives, four main topics have been identified. These are: 1) Analysis of induced seismicity from representative geothermal reservoirs throughout Europe, 2) Understanding the geomechanics and processes involved in creating induced seismicity, 3) Consequences of induced seismicity and 4) Strategies for the mitigation of induced seismicity. The project is coordinated by GFZ Potsdam and involves 12 additional partners. Data from three sites in Iceland, Hengill, Krafla and Reykjanes, will be investigated. These sites are situated in comparable volcanic settings, but with very different seismic response to injection and therefore offer a great opportunity to study the influence of particular parameters on induced seismicity.
34 Hellisheiði high temperature field, SW-Iceland geology, hydrothermal alteration and permeability structures Sveinborg Hlíf Gunnarsdóttir, Helga Margrét Helgadóttir, Sandra Ó. Snæbjörnsdóttir and Steinþór Níelsson School of Engineering and Natural Sciences, University of Iceland Msc The aim of this project is to define the characteristics and the nature of the Hellisheiði geothermal field in SW-Iceland by: - Determining and analysing the different rock formations. - Identifying the connection between permeability and geological structures. - Identifying upflow zones. - Creating a 3D model of the area using state-of-the-art computer software. The Hengill central volcano includes one of the largest geothermal fields in Iceland covering about 110 km 2. It is located at a triple junction where two active rift zones (Western Volcanic Zone and Reykjanes Peninsula) meet a seismically active transform zone (Southern Iceland Seismic Zone). The Hellisheiði high temperature field is part of the low resistivity anomaly of the Hengill region and is situated in its southern sector. The field has been divided into four areas: Skarðsmýrarfjall, Reykjafell, Hverahlíð and Gráuhnúkar and in each of them three wells have been analysed in terms of geology, permeability and hydrothermal alteration. The geological data is primarily based on the analysis of cutting samples collected at 2 m intervals during drilling and petrographic studies from selected depths within the wells. In addition to this temperature logs, XRD studies on clays and geophysical borehole logs (resistivity, caliper, neutron-neutron and natural gamma) are also used. With all this combined it is possible to determine rock formations and intrusives, hydrothermal alteration and permeability structures in the area. The data will be integrated into a 3D model using Petrel, a powerful 3D reservoir software which will be helpful in the comparison between the four areas. The dominant rock formation in the Hellisheiði field is hyaloclastite (tuffs, breccias and pillow lavas) formed sub-glacially. This is to be expected as the area is a part of the Hengill central volcano where sub-glacial rock formations pile up. Lava successions from interglacial periods flow to the lowlands and are therefore less common. By comparing alteration temperatures in the wells with formation temperatures it is possible to determine the state of the geothermal system. Certain temperature dependant minerals are
35 used to determine the alteration temperature, e.g quartz precipitates at the minimum temperature of 180 C and actinolite at 280 C (e.g. Kristmannsdóttir 1979, Franzson et al. 2008). If the minerals indicate temperature that is higher than the current formation temperature it is suggested that cooling has occurred. If, on the other hand, the alteration temperature is lower than the formation temperature recent heating of the area is likely. The distribution of formation temperatures and hydrothermal alteration indicates three upflow zones within the Hellisheiði and Hverahlíð reservoirs. These are situated beneath Gráuhnúkar, Reykjafell and Hverahlíð (Helgadóttir et al., 2010). Minor cooling seems to have occurred west of Skarðsmýrarfjall where the alteration temperatures are considerably higher than the formation temperature would suggest. A cooling front also seems to invade from the east towards Reykjafell between Hverahlíð and Skarðsmýrarfjall. Places of apparent heating up are beneath Gráuhnúkar and in Hverahlíð. The relationship between geological factors and the number and size of aquifers is quite complex. By doing a detailed study of the geology in the wells and comparing the data to the aquifers it is possible to get an idea of this relationship. Stratigraphic boundaries are the dominant factor in the upper part of the wells but below 1600 m b.s.l. no aquifers have been related to stratigraphic boundaries. From 200 m b.s.l. intrusions become a more important factor and from 1000 m b.l.s. the majority of the aquifers have been linked to either intrusions or unknown factors. This result concurs with earlier studies (e.g. Franzson 1998). References Franzson, Hjalti. ʺReservoir geology of the Nesjavellir high-temperature field in SW-Iceland.ʺ Proceedings 19th Annual PNOC EDC Geothermal Conference, Makati City, Philippines, 5-6 March, Franzson, H., R. Zierenberg and P. Schiffman, ʺChemical transport in geothermal systems in Iceland. Evidence from hydrothermal alterationʺ. Journal of Volcanology and Geothermal Research 173, 2008: Helgadóttir, H.M., S.Ó. Snæbjörnsdóttir, S. Níelsson, S.H. Gunnarsdóttir, T. Matthíasdóttir, B.S. Harðarson, G.M. Einarsson and H. Franzson. ʺGeology and Hydrothermal Alteration in the Reservoir of the Hellisheiði High Temperature System, SW-Iceland.ʺ WGC, Bali, Indonesia, April Kristmannsdóttir, Hrefna, ʺAlteration of basaltic rocks by hydrothermal activity at C.ʺ Developments in sedimentology (27), 1979:
36 Simulation of Steam Separators using Smoothed Particles Hydrodynamics Heimir Hjartarson 1, Halldór Pálsson 1 and Magnús Þ. Jónsson 1 1 Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, University of Iceland, Hjarðarhaga 2-6, 107 Reykjavik, Iceland) Educational level Phd In geothermal power plants, a pipe system is used to gather fluids from production wells and transport them to a power plant, or to steam separators. In the case of hydrothermal systems as in Icelands, where the geothermal fluid is a mixture of steam and water, this gathering system is normally designed for two-phase flow. To produce power from the two-phase geothermal fluid one has to separate the fluid into steam and water using steam separators, thus making steam separators an important part of electricity generation. The most common type of separator used for geothermal application is a vertical centrifugal separators, although in Iceland the drum type separator have been more popular . The separators are large and expensive pressure vessels and any allowable size reduction or shape change could significantly reduce capital cost of future geothermal power plant projects. An important part of the design process is to determine flow conditions (or regimes) in the pipes and other components as well as pressure variations. The smoothed particle hydrodynamics (SPH) method is a meshfree Larangian method that has recently gained increased interest in computational fluid dynamics (CFD). The method is particularly beneficial in case of complex multiphase flow [2,3]. The dominant numerical methods in CFD are grid or mesh based methods like Finite Volume Method (FVM), but when dealing with free surfaces, deformable boundary and moving interface can lead to difficulties. The meshfree methods like SPH could be more reliable in this kind of situations because instead of representing the system as grid, SPH uses set of particles, which have material properties and interact with each other within a range controlled by a weight function. In this work, the SPH method is programmed and implemented in C++, based on recent publications in the field. A well known case of a shock tube in one-dimension is modeled with good results and the the problem is extended to three-dimensions. The next step for the work is implementing twophase flow calculations with different particles representing each phase. The separation process will then be studied using smoothed particle hydrodynamics (SPH). The model will be validated using an experimental setup, using air and water at atmospheric pressure and also using measurements from a real geothermal separator. The final result will be a tool that can be used to simulate two-phase flow in both pipes (wellbores or surface pipes) and steam
37 separators and could be used to improve design of geothermal steam separators. Also there will be contributions for improving SPH as numerical method for CFD problems. References  C. Ballzus, Th. Karlsson and R. Maack, Design of Geothermal Steam Supply Systems in Iceland. Geothermics 21(5/6), (1992)  G. R. Liu and M. B. Liu, Smoothed Particle Hydrodynamics: a meshfree particle method. World Scientific publishing (2003)  M. Liu and G. Liu, Smoothed Particle Hydrodynamics (SPH): an Overview and Recent Developments. Archives of Computational Methods in Engineering 17, (2010)
38 Utilization of Supercritical Geothermal Fluid Hjartarson, S.1, Harvey, S. W.2, Pálsson, H.3, Ingason, K.4, Sævarsdóttir, G.5 1Engineering, Reykjavik Energy Graduate School of Sustainable Systems, Iceland 2School of Science and Engineering, Reykjavik University, Iceland 3Engineering and Natural Sciences, University of Iceland, Iceland 4Mannvit Engineering, Iceland 5School of Science and Engineering, Reykjavik University, Iceland M.Sc. in Sustainable Energy Volatile chloride (HCl) has been reported in geothermal fluids all over the world. When steam containing HCl coming from a dry hole cools to saturation temperature, the hloride dissolves in condensed droplets and forms hydrochloric acid. This can have tremendous consequences for equipment as hydrochloric acid aggressively attacks steel and other metals. Severe pitting corrosion can occur and if this happens in the turbine, cracks can form at the bottom of the pits, which will grow larger with fatigue corrosion and lead to a final breakdown. The Icelandic deep drilling project (IDDP) is dealing with extreme circumstances with high enthalpy HCl containing geothermal steam. Successful corrosion mitigation is essential for the feasibility of the development. There are several possible methods for removing HCl from geothermal steam. The goal of this work is to map the applicability of each steam scrubbing technologies with regard to temperature, exergy and cost.
39 Conduction based closed loop EGS Henrik Holmberg Dept of Energy and Process Engineering, NTNU, Norway The principle of Engineered Geothermal Systems (EGS) is to extract heat from geological structures outside the regions of conventional geothermal systems. For EGS to reach a significant portion of its vast potential, it must be proven that the concept can be applied independent of site conditions. Since the geological and thermal structure of the uppermost kilometers of the crust varies geographically, the method or concept is site dependent. In Norway it has been proposed to construct a conduction based closed loop EGS. The geological conditions in Norway are less favorable compared to other places where EGS projects have been initiated such as in Australia and Germany. However, an EGS system constructed in Norway would primarily supply hot water for e.g. district heating purposes, thus eliminating the low efficiency associated with binary power cycles. The thermal gradient and the thermal properties of the bedrock will be critical for the performance of an EGS constructed in crystalline rock. At NTNU research is being performed on the thermal aspects of the system, this includes thermal modeling and optimization of the system.
40 Thermal modelling and evaluation of boreholes for ground-source heat pump system applications Saqib Javed Building services engineering, Chalmers University of Technology, Sweden. Educational level: PhD. The division of Building Services Engineering at Chalmers University of Technology, Sweden has established a state-of-the-art ground-source heat pump (GSHP) experimental facility. The test facility consists of a nine-borehole thermal energy storage system, three heat pumps, six thermal storage tanks, two dry coolers and multiple heat exchangers. The test facility can be used, among other things, to develop, test and optimize control strategies for different GSHP system configurations, to develop and validate component and system models and to perform thermal response tests (TRTs) under different experimental conditions. This poster and presentation reports on the design and development of the test facility and in addition presents the current status of the GSHP related research at Chalmers. A newly developed and validated mathematic solution to study the short-term borehole response is presented. It is also shown that how the new solution can be used together with the existing long-term response solutions. Moreover, results from a series of TRTs conducted on nine laboratory boreholes are presented. A comparison of TRT results for different test durations and injection rates leads to some interesting conclusions.
41 3D structural geological modeling and stress field analysis as core diciplines in exploration geology for high and low enthalpy geothermal systems Egbert Jolie 1, Nicole Schulz 1, Inga Moeck 1 1 GFZ, Telegrafenberg, Potsdam (Section 4.1 Reservoir Technologies, GFZ German Research Centre For Geosciences, Germany) Msc High enthalpy geothermal systems in tectonically active regions and low enthalpy geothermal systems in tectonically quiet regions may require different approaches in exploration strategies. One of the key questions addresses the structural controls of fluid flow (hydrothermal system) and permeability anisotropy, and respectively their similarities and differences in each setting. This study shall discuss these questions. The core discipline in both approaches is 3D geological modeling and the performance of stress field analysis as fundamental component of geothermal exploration methodology. The study areas are located within the extensional Basin-and-Range-Province in Nevada (USA) and the tectonically comparatively quiet Northeast German Basin. The Bradys Geothermal Field in Nevada is characterized by outcropping reservoir rocks, active geothermal surface manifestations and fracture zones observable on surface. In comparison to the Bradys Geothermal Field the Beeskow System in the Northeast German Basin is a blind system without any surface manifestations. The multi-method approach using 1) geological base information and structural surface data, and 2) borehole data and processed seismic data (if available) represents the foundation of the proposed exploration strategy. Stress field analysis should be a major part in geothermal exploration technique of fracture controlled geothermal systems. The method is applicable even in early stages of the exploration phase by frictional constraints when no drilling data are available. In combination with 3D structural models, fault stress modeling can help to delineate favorable drill sites and zones of high permeability (well path planning), but also allows a more comprehensive understanding of drilling failure. The results of this approach will significantly assist in reducing the geological risk of drilling, but also to better understand, if reservoir characteristics can already be inferred from surface data. Furthermore, it will allow a better understanding of the fluid flow behavior in a geothermal reservoir. The results of such studies could also be used as a basis for the decision making process in the planning of hydraulic stimulation operations (e.g. manageable reservoir pressures).
42 Sulphur and metal transport in active geothermal systems, Iceland Hanna Kaasalainen 1,2 and Andri Stefánsson 2 1 Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Iceland, 2 Institute of Earth Sciences, University of Iceland, Iceland Ph.D. student Geothermal fluids are known to be capable of transporting and depositing significant amounts of sulphur and metals. The composition of geothermal fluids depends on the fluid source, extent of water-rock-gas interaction that is enhanced by the input magmatic components in volcanic areas, and processes such as depressurization boiling, cooling, phase segregation and mixing. The major elemental composition of aquifer fluids in Iceland is considered to be controlled by secondary mineral-fluid equilibria except for B and Cl that are highly mobile. This may not, however, apply to all types of geothermal waters or to trace elements. Moreover, general redox disequilibrium often prevails in natural geothermal waters and the chemistry of redox sensitive elements is considered to be kinetically or source controlled. The purpose of this study is to understand the chemistry of sulphur and metals in the different parts of active geothermal systems. Fluid samples of hot springs, mud pots, acidsulphate waters, soil-water profiles, well and steam vent discharges were collected from various geothermal areas in Iceland. Samples were analyzed for major and trace elemental composition, and in most cases also for sulphur redox speciation including sulphide and sulphate that are the most common oxidation states as well as intermediate sulphur species (SO 2-3, SO 2-3, S x O 2-6 ). Special emphasis was put on the geothermal surface environments that are characterized by hot springs, mud pots, steam vents and acid-alteration. The samples showed wide range of chemical composition with temperatures ranging from <50 to >200 C, and ph between 2.01 and Based on the major elemental composition, three different water types could be distinguished, namely (1) NaCl-waters, (2) Acid-sulphate waters and (3) Mixed waters. NaCl-waters had neutral to alkaline ph-values with Na, Cl and SiO 2 together with SO 4, CO 2, H 2 S, F, Na, and K being the major ions. Transition metal concentrations were typically <1 ppb, whereas concentrations trace alkali elements, As Sb, W and Mo were in the upper ppb-scale. To a large extent, they represent aquifer fluids that have undergone depressurization boiling with ascent to the surface and/or mixing with shallower ground waters. Depressurization boiling of the aquifer fluids results in
43 steam rich in volatiles like H 2 S and CO 2 that may segregate from the boiled waters, rise through and condense in shallow oxidized cold ground- and/or surface waters forming steamheated surface waters. In addition to major gases, the steam may also carry trace volatiles such as B and As. In oxidized conditions, H 2 S tends to oxidize to sulphuric acid that effectively leaches the surrounding rock, enhancing metal mobility. Thus, steam-heated acidsulphate are characterized by ph<4, with SO 4, SiO 2 and Mg, Al and Fe being the major ions with concentrations of most transition metals (e.g. Mn, Zn, Cr, V) reaching hundreds of ppb to ppm-level. However, Cl and CO 2 concentrations are low due to steam dilution and degassing, respectively. The variability in the composition of the acid-sulphate waters within an area in depending on the time suggested highly dynamic surface system. Elemental water-rock ratios indicated that primary rock dissolution changed from incongruent in NaCl-waters towards nearly stoichiometric dissolution associated with steamheated acid-sulfate waters. Elements often considered immobile including Al, Mg and most transition metals were mobilized with decreasing ph conditions. In case of some elements (e.g. Ca, Ba), secondary mineral formation likely controlled their concentrations in acidsulphate waters that typically were undersaturated with respect to most secondary phases. Aqueous speciation calculations suggested metals to be present as simple ions, hydroxo-, carbonate- and sulfide-complexes in NaCl-waters, whereas simple ions and sulfate complexes dominated in steam-heated acid sulphate waters. The major and trace elemental chemistry in the geothermal waters is largely influenced by the sulphur chemistry, both due to changes in water ph and redox state and by metal-complexation. In accordance to previous studies indicating general redox disequilibrium in natural surface and geothermal waters, sulphur speciation was found to be dynamic and at redox disequilibrium, meaning that sulphur speciation can not be estimated from bulk analysis and measurements of a given redox state. This has implications also on the understanding the geochemistry of elements associated with sulphur species (As, Sb, Cu, Au etc), many of which being of scientific and environmental interest.
44 Primary Energy Efficiency (PEE) and CO 2 Emissions of Geothermal Utilization - Life Cycle Assessment Marta Rós Karlsdóttir, Ólafur Pétur Pálsson and Halldór Pállson Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, University of Iceland, Iceland Phd The way of life cycle and product chain thinking is emerging its way into the energy sector in Europe as a more appropriate way of comparing different energy production alternatives. Before, the focus has mainly been on the final production stage of the energy production chain which can give a misleading view of the total impact on environment and natural resources for the end product. Energy performance indicators that include the material and energy consumption throughout the whole production stage of different energy production systems are now being introduced in the European Unioun (EU) through the Directive 2002/91/EC of the European Parliament and of the Council on the energy performance of buildings and the European Standard EN15603 on the energy performance of buildings. In the directive, a common methodology is introduced to calculate the energy performance of buildings and energy certification of new and excisting buildings in the resdidential and tertiary (offices, public buildings, etc.) sector. The energy certification requires that indicators on the energy performance of buildings include the consumption of primary energy and the CO 2 emissions resulting from the buildings energy usage . In the Directive 2002/91/EC, two energy performance indicators are defined based on the entire production chain of the energy delivered to consumers; Primary energy factor (f p ) and CO 2 emission factor (K). These factors describe the greenhouse gas emissions in CO 2 equivalents and how much primary energy is needed per unit (kw, MWh, etc.) of energy (power or heat) delivered to the consumer. Primary energy is further defined as energy that has not undergone any conversion process such as crude oil, natural gas, solar-, wind-, hydro- and geothermal energy . The factors are also discussed in EN15603, where calculation methods and energy performance indicators for various energy sources are published . Primary energy consumption and CO 2 emissions from energy chains are not only based on the consumption of fuel (or other energy resources) in the power or heat generation process, but also on all the primary energy needed and CO 2 emissions resulting from the construction, operation and possibly demolition of the production facilities. Also, some primary energy is needed and emissions released during the distribution of energy. To calculate such
45 accumulated primary energy consumption and CO 2 emissions, the method of life cycle assessment (LCA) is well suited. The calculation of these factors for geothermal based heat and power production has had little attention, despite the fact that 11 countries within the European Union use geothermal power  and other European countries such as Iceland and Turkey, which are not current member states of the EU, also utilize geothermal energy extensively for power production. Also, 32 European countries use geothermal energy directly for various purposes such as for house heating . For countries using geothermal based power and/or heat and comply to EU legislation, it is thus important to have easy access to standardized factors accounting for the primary energy efficiency and CO 2 emissions from geothermal based heat and power The goal of the doctorate study is to perform LCA on geothermal heat and power production processes such as electrical power plants, combined heat and power plants (CHP) and district heating systems. The results of the LCA will be used further to identify the primary energy and CO 2 emission factors for geothermal based heat and power production as defined in  and . To calculate those factors by methods of LCA, inventory information is needed for existing geothermal power plants, CHP plants and district heating systems. In the study, iventory data is collected from Icelandic heat and power production facilities using different technological solutions for their production. References  EU. (2003, January 4). Directive 2002/91/EC of the European Parliament and of the Council of 16 December 2002 on the energy performance of buildings. Official Journal of the European Communities.  EN 15603:2008. Energy performance of buildings. Overall energy use and definition of energy ratings. Geneva: International Organisation for Standardisation (ISO).  R. Bertani, Geothermal Power Generation in the World Update Report. Proceedings World Geothermal Congress 2010, (April 2010)  J. W. Lund, D. H. Freeston, T. L. Boyd, Direct Utilization of Geothermal Energy 2010 Worldwide Review. Proceedings World Geothermal Congress 2010, (April 2010)
46 Optimized geothermal binary power cycles using R134a and R410A Evgenia Kontoleontos 1, Dimitrios Mendrinos 2, Constantine Karytsas 3 1 Parallel CFD and Optimization Unit, Laboratory of Thermal Turbomachines, School of Mechanical Engineering, National Technical University of Athens, Greece, PhD candidate 2,3 Geothermal Energy Department, Centre for Renewable Energy Sources and Saving, Greece This paper presents the modelling and the optimization of geothermal Organic Rankine Cycles using R134a and R410A as working fluids in a geothermal binary power machine that generates electricity from low temperature geothermal resources with profitable operation down to 65 C. This research focuses on the modelling of the ORC heat exchangers (evaporator and condenser) for R134a and R410A according to the heat exchanger type. For the modelling of the evaporator a plate heat exchanger is used, while for the modelling of the condenser a shell and tube and a plate heat exchanger are used in order to compare the impact of the use of these two types of condenser to the net overall efficiency of the plant. The objectives of the optimization are the maximization of net overall efficiency and the minimization of the cost of the plant, which is represented by the minimization of the exchangers surface. Through this research, a set of optimal solutions (optimal front) for an ORC machine, that combines maximum plant s efficiency and minimum cost, is obtained. A preliminary design of the heat exchangers is also obtained for each optimal solution. The optimization is based on EASY, an evolutionary algorithm code. The results of the optimization of the ORC machine with working fluid R134a and R410A are plotted in Fig. 1. The net overall efficiency in relation to the heat exchangers surface is presented, where a plate heat exchanger is used for both the evaporator and the condenser. The comparison between the two working fluids shows that R134a performs better than R410A in this temperature profile, where the maximum possible net overall efficiency reaches the value of 5.6 %. The results of the optimization of the ORC machine with working fluid R134a between a plate and a shell and tube condenser are presented in Fig. 2. The comparison between the net overall efficiency of the two type condensers shows that the optimal front, that represents the plate condenser modelling, is significantly better than that of the shell and tube modelling.
47 R134a R410A exchangers surface Fig. 1: Rankine cycle optimization - optimal solutions for R134a and R410A - the net overall efficiency in relation to the exchangers surface plate condenser shell and tube condenser members of the optimal front Fig. 2: Rankine cycle optimization - the net overall efficiency of each member of the optimal front for R134a between a shell and tube and a plate condenser
48 Danube Hydrodynamic and heat transport modelling in a Hungarian fractured basements rocks for ranking EGS sites Éva Kun 1, Tivadar M. Tóth 1, Tamás Földes 2, János Viszkok 3, 1 Szeged University, Hungary,, 2 Geotomo Kft., 3 Central Geo Kft Abstract The Pannonian Basin in Hungary represents one of the highest geothermal energy potential area in Europe. The basin is a deep Neogene depression, surrounded by the Carpathian Mountains, filled at places by more than 6000 m of Miocene Pliocene sediments. These are underlain by pre-neogene metamorphic crystalline basement rocks. Bohemian Massif 200 km WESTERN CARPATHIANS VIENNA BASIN BÜKK Eastern Alps Tisza HUNGARY Lake Balaton PANNONIAN BASIN MECSEK EASTERN CARPATHIANS APUSENI TRANSYLVANIAN BASIN Dinarides Papuk SOUTHERN CARPATHIANS In order to efficiently and sustainably exploit this geothermal resource, both water and heat balances need to be fully understood. One component of this understanding is knowledge of the geothermal fluid (i.e. hot groundwater) flow regime in the fractured basement. This, in turn, requires information on the tectonic framework that has shaped these fracture systems and controls their permeability distribution. Unfortunately, direct study of the crystalline basement is impractical and glimpses of the basement can only be caught in deep exploration boreholes. The methods involved taking into account the multi-scale concept are as follows: - classical petrology and structural geology for rock classification; - Computer Tomography to understand internal structure of core samples as well as measure fracture network geometric parameters; - rock mechanics to measure deformation parameters of diverse rock types; - electric logs (CBIL measurements) to follow fracture intensity along selected wells; - fracture network simulation to upscale geometric information;
49 - well-tests and interference tests; - seismic section and attribute evaluation to identify large scale tectonic structure and combine small vs. large scale data; - flow and heat transport modeling. Heat transport and flow modeling process was tested and used as a standard workflow to evaluate, to compare and to rank the geological/ hydrogeological potential of different geothermal prospects. The preliminary studies are confirmed that the lithological units can be characterized different fracture pattern and the different fracture patterns represent well separated hydrogeologic units having different hydrodynamic features as permeability, connectivity, storativity, porosity, etc. The producing well situated on a better fractured amphibole-gneiss zone a more permeable pocket in a less permeable matrix straddled by lesser fractured sillimanite gneiss. This pocket can prevent huge volume of water loss, direct the injected water toward the producing well and assure the heat exchange between rocks and water.
50 Thermal response test with and without artificial convection Heiko T. Liebel 1, Gunnar Vistnes 1, Bjørn S. Frengstad 2, Randi K. Ramstad 3, Bjørge Brattli 1 1 Department of Geology and Mineral Resources Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim 2 Geological Survey of Norway (NGU), P.O. Box 6315, NO-7491 Trondheim 3 Asplan Viak AS, Postbox 6723, NO-7490 Trondheim PhD candidate Introduction Thermal response tests (TRT) are performed in shallow geothermal projects to measure the effective thermal conductivity and the borehole resistance in a well, both important parameters for the dimensioning of a ground-source heat system with closed-loop borehole heat exchangers (Austin 1998, Gehlin 1998). Boreholes in hard rock are mostly non-grouted in Scandinavia but filled with groundwater. During a TRT the borehole equipment, the groundwater and the bedrock is heated up and convective heat transport takes places inside the borehole. The effect of convection due to heated groundwater can be estimated with a Multi-Injection Rate (MIR) TRT (Gustafsson and Westerlund 2010). We repeated the experiment of Gustafsson and Westerlund (2010) in a different geological setting. The result will be compared with a future MIR TRT with induced convection with the help of a groundwater pump. Material and Methods The test borehole is 150 m deep. The groundwater table is about 10 m below the surface. The dominant rock type is a greenstone. Below 93 meters tonalites (i.e. trondhjemite) occur. A water-bearing open fracture appears in 35 m. The TRT trailer used, is property of the Geological Survey of Norway and is built up as described by Gehlin (1998). A single U-shaped borehole heat exchanger was installed in the borehole. Four subsequent TRTs were performed with 3, 6, 9 and 12 kw of heating power and a duration of around 70 hours each. Results and Discussion
51 Figure 1 shows the increase in average heat carrier fluid temperatures throughout the MIR TRT. With increasing heat exchange rate from 18.2 to 72.5 Wm -1, the measured effective thermal conductivities increase (infinite line-source approximation) with 156 %. In the case of Gustafsson and Westerlund the effective thermal conductivity increases only with 35 % (at Wm -1 ). Figure 1. Temperature development of the heat carrier fluid as mean value of inward and outward pipe in a MIR TRT with four steps (numbers in the figure represent: first row electric power input; second row - heat exchange rate; third row effective thermal conductivity) One reason for the strong increase in effective thermal conductivities in our study may be a thermosiphon effect (Gehlin et al. 2003) between the base of the borehole and the main fracture in 35 m depth. Convective flow in the borehole during the MIR TRT was detected with an optical televiewer and recorded as video. Flow patterns are similar as simulated by Gustafsson et al. (2010). Further Work Thermal borehole resistances during the different steps of the MIR TRT will be estimated with the help of Matlab. In addition, a second set of MIR TRT with pumping of groundwater will be performed to induce an artificial convection. The main research question is, if forced convection in the borehole can be used to lower the thermal resistance in a borehole under operation, resulting in more effective ground-coupled heat pump systems. References Austin WA (1998) Development of an in situ system for measuring ground thermal properties. M.Sc. Thesis, Oklahoma State University, Stillwater. OK, USA Gehlin S (1998) Thermal response test. In situ measurements of thermal properties in hard rock. Licentiate thesis. Luleå University of Technology, 1998:37, pp. 73 Gehlin SEA, Hellström G, Nordell B (2003) The influence of the thermosiphon effect on the thermal response test. Renew Energy 28: Gustafsson AM, Westerlund L (2010) Multi-injection rate thermal response test in groundwater filled borehole heat exchanger. Renew Energy 35: Gustafsson AM, Westerlund L, Hellström G (2010) CFD-modelling of natural convection in a groundwater-filled borehole heat exchanger. Appl Therm Eng 30:
52 Mechanical deformation coupled with chemical reactions Magnus Løberg 1 and Yuri Podladchikov 2 1 Department of Geoscience, University of Bergen, Norway 2 Institut de géophysique, Universté de Lausanne, Swiss The introduction of fractures and circulation of water in a multiple-well enhanced geothermal system will put the fluid-rock system out of chemical equilibrium. This condition may induce e.g. dissolution/precipitation chemical reactions. There may also be associated volume changes with the chemical reactions. The transport of possible dissolved material may precipitate at the production well where pressure drops, and in the long run this might clog the system. Also effects on volume changes of the host rock may also induce mechanical deformation. We formulate a continuum mechanical two phase model for the fluid-rock system with possible mass transfer between the phases. For the chemical reactions between the fluid and the rock we will investigate two cases 1) local equilibrium condition and 2) reaction kinetics. Visco-elastic volumetric deformation (porosity evolution) of the rock is controlled by the effetive stress law for a porous medium. Mechanical deformation for the system without chemical reactions (mass exchange) gives rise to so called porosity waves. When the model is extended to allow possible mass exchange, no fundamental new types deformation is appearing, but the chemical reactions alters the parameters of elastic and viscous mechanical response for local equilibrium and reaction kinetics respectively.
53 Figure 1. Shows porosity field and pressure field after some timesteps. Initial condition for porosity is 0.01 everywhere except at the middle of the bottom where it is The plot shows two regions of elevated porosity that are travelling upward. After a certain amount of time, and new region of elevated porosity will develop, and so on. Because of the difference in viscosity for compaction and decompaction the region of elevated porosity does not diffuse out but stays localised. The effective pressure drives the evolution of porosity as it opens pores at the top of the elevated region and closes them at the bottom. The total effect is that the fluid in the pore space are transported in sections rather than as a continous flow.
54 Changing of mineral composition, structure and properties of volcanic rocks as a result of hydrothermal process, Paramushir Island, Fare East, Russia Luchko Maria Engineering and Enviromental Geology, Moscow State University, Russia Bachelor Geothermal energy is a promising area for substitution of fossil fuels. Social and economic activities of the Sakhalin s North-Kuril district are concentrated on Paramushir Island, one of the biggest islands of the Kurils (Fare East, Russia). Several thermal areas are located at Paramushir Island. The largest thermal field of this island is North-Paramushir thermal field. The heat sourse of this system is subvolcanic body of the Quaternary active volcano Ebeco. The main objective of our study is to investigate an alteration of the physical properties, structure and composition of tuffs under the action of hydrothermal process. We compare two groups of tuffs. The first group consists of fresh, unaltered tuffs, which were sampled out of the thermal field. The second group includes hydrothermally altered tuffs, collected inside of hydrothermal system on the slope of Ebeco volcano from several boreholes. The following properties were studied: density, porosity, hygroscopy, velocity of longitudinal and transversal waves, geomechanical characteristics (compressive and tensile strength, elastic modulus), magnetic susceptibility. Composition and structure of tuffs were studied by means of optical microscope in thin sections and X-Ray analysis. 56 samples of tuffs were investigated (20-unaltered, 36-altered). Mineral composition of fresh tuffs is sodium-calcium feldspar, pyroxene, volcanic glass and sometimes glauconite. Altered rocks belong to different types of alteration: high- and low-temperature propylites, argillic rocks, and opalites. The magnitude of alteration varies from slightly to intensively altered. Hydrothermal alterations reflect in rocks properties. Basically changes of rocks mineral composition and structure cause an increase of density and strength, and a decrease of porosity. These researches give information about rocks petrophysical properties which help to solve different tasks of geosciences.
55 Dissolution of basaltic glass in seawater at C and 70 bars CO 2 pressure Implications for CO 2 mineral sequestration K.G. Mesfin, D. Wolff-Boenisch and S.R. Gislason Institute of Earth Sciences, University of Iceland, Sturlugata 7, 101 Reykjavik, Iceland Mineral sequestration of CO 2 in mafic rocks offers a long-term trapping of CO 2. It requires the combination of divalent metals with dissolved CO 2 to form carbonate minerals. This method of in-situ CO 2 sequestration is a long lasting method as the resulting carbonates can be stable for millions of years. The most copious sources for these divalent cations are dominantly peridotitic and basaltic rocks rich in Mg, Fe, and Ca. The rapid dissolution rates of silicate minerals in these rocks results in consumptions of protons and release of divalent metals which enhances the formation of carbonate minerals. Various methods have been proposed for the CO 2 injection, such as separate supercritical CO 2 phase or CO 2 fully dissolved in water. Both end-members have drawbacks. Supercritical CO 2 is less dense than its surrounding fluids and rocks, which will pose problems in fractured basaltic rocks. To fully dissolve 1 ton of CO 2 at 25 C, 27 tons of water are needed. This water demand limits the applicability of this method of injection in the terrestrial environment but in coastal areas and on the ocean floor there is endless supply of seawater. We have carried out experiment at 100 C and 70 bars CO 2 pressure to address the effect of sea water on the dissolution rate of MORB glass (Mid Ocean Ridge Basalt). The experiment imitates conditions that exist within the oceanic crust at about 450 m depth of CO 2 injection. We use a 6.4L pressure vessel from Parr Instruments constructed from T4 grade titanium. The vessel is equipped with gas inlet valve, liquid sampling valve, burst disk, gas release valve and a pressure gauge. Temperature is controlled by placing the pressure vessel inside a heater which is also responsible for attaining the desired pressure in the system. Sea-water collected far off the SW shore of Iceland was placed inside the reactor together with powdered and washed basaltic glass (45-125μm size fraction) and pressurized with CO 2 using a CO 2 cylinder source up to ~45 bars. The vessel was then heated causing the internal pressure to increase to 70 bars, driving the CO 2 into supercritical conditions. Periodic pressurized samples have been taken to monitor the solute concentration and thus reaction progress. A sampling cylinder connected to the liquid sample valve is used to sample from the pressure vessel. The sampling procedure is based on creating a pressure gradient between the sampling cylinder and the reactor, the pressure on the vessel being higher than that of the sampling cylinder. The CO 2 from the sample is then collected into a 0.5M KOH base and the dissolved inorganic carbon (DIC) subsequently analysed using IC. Results of this experiment with respect to the evolution of solute chemistry and the precipitation of secondary phases will be presented.
56 Thermal Response Testing and Evaluation Helena Nakos Building Services Engineering, Chalmers University of Technology, Sweden Msc The design of a ground source heat pump (GSHP) system depends on the ground thermal properties. These properties include ground thermal conductivity, borehole thermal resistance and undisturbed ground temperature. These properties can vary for different geographic locations and are hence calculated from an in-situ thermal response test, when designing a large-sized GSHP system. Numerous methods have been developed to evaluate the experimental data obtained from a thermal response test. The most commonly used methods include the analytical line-source approximation method and numerical methods developed by Shonder and Beck (1999) and Austin et al. (2000). All these methods have their limitations and thus render room for development in this field. This project aims at the development of a new method to evaluate thermal response tests. The new method will consider the thermal capacities, resistances and properties of all the borehole elements and is hence expected to be valid even for short times. This can reduce the required duration for which the thermal response tests are needed to be conducted. The new method will be validated using existing methods and a series of in-situ thermal response tests.
57 Structural Control Over Hot Springs in Sipoholon Geothermal Prospect, North Sumatera, Indonesia : a preliminary data update Mochamad Nukman *), Inga Moeck Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences Section 4.1, Reservoir Technologies GFZ Telegrafenberg, Potsdam, Germany. *) PhD student Sipoholon is located in Tarutung basin in southern of Toba Lake, North Sumatera, Indonesia. Sumatera is bisected by 1900 km dextral strike slip as a consequence of oblique subduction system between Indian-Australian and Eurasian plate. This fault system is well known as Sumatera Fault System (SFS) trending NNW-SSE which generates several interpreted pull apart basins along the island which some of them hosted geothermal manifestations. One of those interpreted pull a part basin is Tarutung basin (also known as Sipoholon graben). Current update field visit at Sipoholon shows that 7 hot springs with temperature range C are located at Eastern part of basin and are in line with regional structures trend. Updating and revisiting these manifestations is easily conducted by just following the trend of existed structure trend. The largest manifestation is centered to the Northerpart of Tarutung basin, i.e. Ria-Ria, which in association with massive travertine terrace. Most of others hot springs are associated with massive travertine terrace, and some others (i.e. Air Soda, Parbubu, Pulopulosatu, Ignasia) are associated with altered pyroclastic and lava. One medium size of hot spring is located at the southern-end of the basin, i.e. Paeraja Spring with 44 0 C, is also associated with travertine. Structure evidences around these manifestations were observed and measured. Some riedel shears structures were also observed within the spring (i.e. Hutabarat, C) and around the major structure (i.e. Ria-Ria) showing indication of dextral strike slip fault NNW SSE. The existence of normal fault at the western Tarutung (6 km to the East of Sipoholon) with strike NNW which has similar trend with SFS shows the evidence that Tarutung pull apart basin has also transtensional component. This normal fault is also associated with Panabungan hot spring ( C) which is located at about 200 m of its west.
58 Indonesian Site-Specific Design Optimization of Subcritical Organic- Rankine-Cycle Geothermal Power Plant Yodha Y. Nusiaputra 1 1 Institute for Nuclear and Power Engineering, Karlsruhe Institute of Technology (KIT), Germany PhD Indonesia may have the highest geothermal power potency of any nation. Trial calculations indicate that 40% (equivalent of approximately 27,189 MW) of geothermal energy in the earth s crust is released in the Indonesian archipelago and neighboring areas. However, only 1197 MW of electricity generated from geothermal energy has been used as of It is quite apparent that the geothermal resources in Indonesia have been underdeveloped in spite of their huge potency. Generally, geothermal fluids used for electricity generation have temperature above 200ºC. But there are also middle and low temperature fluids that can be used for electricity generation. Developing such resources is also important due to extend the utilization potency. These potencies are abundant in remote areas like in Flores, Maluku, and Sulawesi. Recently, these remote areas are still electrified by diesel power plant which uses oil as fuel. The government subsidies for this oil consumption is quite high, almost 30% from national electricity generation operational cost. To address this concern, a small-scale geothermal power plant is being alternative to replace diesel power plant. A subcritical Organic-Rankine-Cycle with pure working fluid technology is chosen for the application since it is has proven-reliability. This thesis is aiming in optimizing subcritical Organic-Rankine-Cycle module site specifically for Indonesian boundary conditions. For the initial step, a prototype of 60 kwe n- butane binary module is presented. Simulation of the prototype module and its components will be carried out. In order to validate the simulation model, instrumentation and testing of the prototype module at the geothermal research site Groß Schönebeck (Germany) will be done. Analysis and evaluation of the measured data, as well as development and validation of numerical prototype model will be carried out by comparing measured data and simulation results.
59 The validated model will then be used for further simulation studies on demonstration plant at Sibayak (Indonesia). Thermo-economic module optimization considering the specific boundary conditions of remote areas (e.g. module capacity, module assembly, process design, component and material selection, control engineering) will be performed. The simulation results completed with several considerations of operation and maintenance parameters will be presented in Process Flow Diagram, Process and Instrumentation Diagram and System Note. Simple financial analysis will also be performed to check feasibility of the power plant to replace diesel power plant.
60 COMBINING ADAPTATION AND MITIGATION ASPECTS OF CLIMATE CHANGE IN GEOTHERMAL DEVELOPMENT Pacifica F. Achieng Ogola 1 and Professor Brynhildur Davidsdottir 2 and Dr. Ingvar Birgir Friðleifsson 3 PhD Student at the University of Iceland, UNU-GTP Iceland and Kenya Electricity Generating Co. Ltd 1 Director of UMAUD Environment and Natural Resources Studies at the University of Iceland 2 Founding director United Nations University Geothermal Training Program, UNU-GTP Iceland 3 Geothermal energy is considered clean and renewable/sustainable and has been used in mitigation of climate change. However, the extent of its vulnerability to climate change, potential for use in adaptation as well as its contribution to maladaptation has been downplayed. The research seeks to identify how geothermal energy can be used in reducing the impact of recurrent drought within the Kenyan rift system as well as its contibution towards the millenium development goals (MDGs). It also identifies the potential of geothermal develoment and use in undermining adaptation efforts or causing maladaptation. The extent of vulnerability of hydrothermal systems to continuous water stress caused by increasing global warming, rapid water catchment degradation (recharge areas), and unsustainable use geothermal resources is also assessed. Unlike adaptation, mitigation aspects of geothermal systems are clearly understood and institutionalised under the climate change regime.the research therefore proposes a new conceptual model called the Geo-AdaM for combining and mainstreaming both adaptation and mitigation aspects in geothermal development. It also identifies new aspects of utilization within the Kenyan Central Rift which are key in combating the impacts of drought in a newly adapted Lindal diagram. The results of this study can be upscaled within the entire African rift and other regions where applicable.
61 Abstract Auður Agla Óladóttir The object of this study is to quantify changes in soil heat and CO 2 flux in the geothermal area in Reykjanes Peninsula and to understand weather recent observed changes are natural or related to the onset of HS Orka s power plant in The study is based on yearly measurements of soil heat gradient and soil CO 2 flux since The CO 2 emission was measured applying accumulation chamber methodology, which allows quick direct measurements of the CO 2 flux from soil without drastically altering the natural flux in a wide range of fluxes. Both soil temperature and CO 2 flux measurements were carried out on a grid with 25 m x 25 m resolution. Mapping of the temperature was done by using kriging interpolation algorithm. Sequential Gaussian simulation (sgs) was used to generate 100 realizations of CO 2 flux for the area. Probabilistic summary of these simulations were used to map the flux and to calculate the total CO 2 output for each year. Another aim of the study is to increase knowledge of using infrared images (TIR) for exploring geothermal areas. Thus, TIR images will be fundamental data to obtain heat flux from geothermal areas and may as such be used for surveillance of natural changes in surface activity and changes due to geothermal power production. TIR images will be obtained of the geothermal area in Reykjanes in spring 2011 and simultaneous soil temperature measurements.
62 Influence of weather on hydrogen sulfide distribution in Reykjavik City Snjólaug Ólafsdóttir 1, Sigurður Magnús Garðarsson 2 1 PhD student, Faculty of Civil and Environmental Engineering, University of Iceland, Iceland 2 Professor, Faculty of Civil and Environmental Engineering, University of Iceland, Iceland Gases emitted from geothermal power plants are among the key environmental factors of concern for the development of geothermal power plants. Sulfur gases are of most concern but also trace gas and carbon dioxide (CO 2 ) emissions. Sulfur is emitted from geothermal areas as hydrogen sulfide (H 2 S), and when the areas are developed the emission is increased. H 2 S is a volatile compound that may be oxidized in the atmosphere. Several environmental factors can influence the H 2 S concentration in the atmosphere, such as precipitation, temperature, wind speed, radiation and concentration of other chemicals. Geothermal power production in the vicinity of Reykjavik City has increased considerably during the last few years. Electricity production at Nesjavellir Geothermal Power Plant started in 1998 and in October 2006 the Hellisheidi Geothermal Power Plant started operation and was enlarged in the fall of The Department of Environment of Reykjavik City started measuring hydrogen sulfide (H 2 S) concentration at Grensasvegur Street in February In August 2007 H 2 S measurements started in Hvaleyrarholt, Hafnarfjördur, and in June 2008 in Kopavogur town. In 2010 three new stations started measuring one in Nordlingaholt, the eastern most district in Reykjavik, one in Hveragerdi the town east of Reykjavik but west of the power plants and one at Hellisheidi Power Plant. These tree stations are owned by Reykjavik Energy. The main objective of this research is to shed light on which parameters influence the concentration of hydrogen sulfide in Reykjavik City and its surroundings. The hydrogen sulfide concentration in Reykjavik rises when the wind is coming from the east since the power plants are located east of Reykjavik. Here events with winds coming from the east for 2 hours or more are analyzed. The mean hydrogen sulfide concentration during each event is compared to the length of each event and weather factors. There does not seem to be a direct correlation between the length of time in which the wind is coming from the east and the concentration, other factors have to be taken into account also. Wind speed has a large effect on the concentration the higher the wind speed the better the mixing in the atmosphere. Comparing the mean wind direction of these events with the mean H 2 S concentration shows that the highest concentrations are between 85 and 110 wind. This indicates that topography influences the movement of the H 2 S because for it to go a straight line from Hellisheiði Power Plant to Grensasvegur measuring station it would be at 116 wind. Precipitation also has an effect on the concentration and the highest concentration is measured when there is little or no precipitation.
63 Toxic metal mobility following the injection of CO 2 into basaltic aquifers. J. Olsson 1,2*, S. L. S. Stipp 2 and S.R.Gislason 1 1 Nordic Volcanological Institute, Institute of Earth Sciences, University of Iceland, Sturlugata 7, 101 Reykjavik, Iceland. 2 Nano-Science Center, Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 København Ø, Denmark. Corresponding author: Educational level: Msc. Injection of CO 2 into rocks creates corrosive CO 2 charged waters with the ph of 4 to 3 . The low ph can lead to mobility of toxic metals at the early stage of water/rock interaction . Dilution and rock dissolution, especially of mafic rock, will increase the ph and lead to precipitation of carbonates and other secondary minerals. The question remains, how fast are the toxic metals sequestrated by precipitation and/or adsorption to the secondary minerals. The 2010 eruption of the Eyjafjallajökull volcano, Iceland, provides a unique opportunity to study the mobility of toxic metals, related to the injection of CO 2 into shallow basaltic aquifer and the ensuing precipitation of carbonates. Following the first phase of the eruption from 20 March to 12 April 2010, the change in conductivity of the rivers in the vicinity of the volcano was mostly associated with direct contact of surface waters with new lava or ash. However, in July 2010, a new strong outlet of riverine CO 2 was observed on the north side of the volcano via the river Hvanná, which indicates deep degassing into the water. A white mineral layer; at some places more than 1 cm thick, for hundreds of meters downstream was observed. The precipitation was identified solely as calcite with X-ray diffraction. A gradual decrease of; the conductivity from 1.8 to 1.1 ms/cm, alkalinity from 20.8 to 8.8 meq/kg, the concentration of Ca, K, Mg, Sr, SO 4, Ba and CO 2, and an increase in the ph from 6.5 to 8.5, were strongly correlated to the amount of precipitated travertine. The water temperature was below 5 C and an elevated atmospheric CO 2 partial pressure was detected near the river. The river water degassed downstream, ph increased, resulting in calcite supersaturation and precipitation as commonly observed in travertine deposits . We are currently measuring the bulk aquatic and travertine trace metal concentrations, and the surface composition of the calcite will be studied. This study can reveal whether the calcite scavenges toxic metals such as As, Cr and Cd, that are released during the early stage of water-rock-co 2 interaction at low ph [2,4]. References  S. R. Gislason, et al., International Journal of Greenhouse Gas Control 4, pp. 537 (2010)  T. H. Flaathen, et al., Applied Geochemistry 24, pp. 463 (2009)  Ø. Hammer, et al., Geofluids 5, pp. 140 (2005)  B. Sigfusson, et al., Environmental Science and Technology 42, pp (2008)
64 Transport and precipitation of carbon and sulphur in the Reykjanes geothermal system, Iceland Kevin Padilla 1, Andri Stefánsson 1, Thrainn Fridriksson 2 1 Department of Earth Sciences, University of Iceland, Sturlugata 7, 101 Reykjavík, Iceland 2 ÍSOR, Iceland GeoSurvey, Grensásvegur 9, 108 Reykjavík, Iceland MSc student The effect of naturally occurring processes including fluid-rock interaction, boiling and cooling on carbon and sulphur transport and mineralization in the Reykjanes geothermal system was studied, using both well-scale analysis and geothermal fluids composition and modelling. Aquifer temperatures in the Reykjanes geothermal system range from 275 to 310 C with ph between 4.5 and 5.0, Cl concentrations of 16,650-20,035 ppm, CO 2 partial pressures of bar and H 2 S partial pressures of bar. Aquifer CO 2 and H 2 S partial pressures were found to be controlled by the mineral buffers clinozoisite + prehnite + calcite + quartz and by pyrite + prehnite + magnetite + quartz + anhydrite + clinozoisite, respectively. Upon ascent to the surface, the geothermal fluid boils due to depressurisation resulting in CO 2 and H 2 S partition into the steam phase and ph increase of the boiled water. As a consequence, the non-volatile elemental concentrations increase in the water phase whereas the volatile elemental concentrations decrease. However, the interplay between ph and degree of degassing resulted in an initial increase of aqueous species activities of some volatile elements including CO 2-3 and HS -. This results in complex effects of boiling upon carbonate and sulphur bearing mineral precipitation. Upon initial boiling, calcite was observed to become supersaturated resulting in potential mineralization. Extensive boiling may, however, eventually cause calcite undersaturation. Pyrite was observed to become supersaturated after extensive boiling. The effect of cooling is reflected in decreased ph in water. These changes enhance calcite solubility resulting in calcite undersaturation in the cooled water. Pyrite becomes supersaturated upon conductive cooling as its stability and therefore potential precipitation from solution is promoted with decreasing temperature. The results were compared with mass of carbonates and sulphides in drill cutting samples collected at various depths from wells number RN-10 and RN-17. Measured carbon content in the geothermal altered rocks, increases with decreasing depth from ~0.01 up to ~2.0 wt% in the depth range of ~ m. Below 1100 m, carbon content does not show any trend with respect to depth with values in the range <0.5 ppm to 0.03 wt%. On the other hand, sulphide
65 depth(m) depth(m) concentrations in rocks range from <0.01 to ~1.2 wt% and unlike for carbon content no obvious trends as a function of depth were observed (see Figure 1). Accordingly, it is concluded that calcite precipitation from up-flowing geothermal fluids occurs upon boiling in the upper ~1100 m of the system. Sulphide precipitation mainly as metal sulphides like pyrite seems to take place throughout the system and is influenced by many factors including sulphide mineral composition and solubility, temperature, ph, and boiling a b RN10 RN Total carbon wt% Figure 1. Mass content of (a) total carbon and (b) sulfide sulphur measured in drill cuttings from wells RN-10 and RN-17 as a function of depth. RN10 RN Sulphide sulphur wt%
66 The Euganean geothermal field (NE Italy): a new hydrothermal structural model Marco Pola 1, Paolo Fabbri 1, Dario Zampieri 1 1 Dipartimento di Geoscienze, Università degli Studi di Padova, Padova - Italy contact: Educational level: PhD student The Euganean Geothermal Field (EGF) is the most important thermal field in the northern Italy. It is located in Veneto, east of the Euganei Hills and southwest of Padova. The EGF extends on a plain band of 36 Km 2 and comprises Abano Terme and Montegrotto Terme, two famous spa towns. At present about 250 wells are active and the total average flow rate of exploited thermal fluids is 15 Mm 3 /year. Physical and chemical parameters of the Euganean thermal waters were statistically analyzed by several authors: the temperature ranges from 60 C to 86 C, and their T.D.S. is 6 g/l with a primary presence of Cl and Na (70%) and secondary of SO 4, Ca, Mg, HCO 3, SiO 2. 3 H and 14 C measurements suggest a residence time greater than 60 years, probably a few thousand years. The analyses of the Oxygen isotopes show that the thermal waters are of meteoric origin and infiltrate in an area up to 1500 m a.s.l.. The previous conceptual model [Piccoli et al., 1976] located the recharge zone of the thermal circuit 80 Km northwest of the EGF. The meteoric waters infiltrate in Mesozoic carbonate formations, uplifted in the footwall of a normal fault separating the chain from the foredeep, and flow inside it. They warm up by a normal geothermal gradient and then rise quickly in the EGF, thanks to the high fracturing of the rocks. Due to a misunderstanding of the structural setting (the uplifted block is the hanging wall of a south-verging thrust) and the use of an idealised (wrong) cross section, this model cannot work. The thrust uplifts the crystalline basement that crops out downstream of the recharge zone. Therefore, the low permeable metamorphic rocks of the basement hydrogeologically isolate the recharge area from the outflow parts of the thermal circuit. More recently, it has been proposed that the EGF is located above a left stepover structure (relay zone) of the Schio Vicenza fault system (SVFS) covered hundred meters beneath the alluvial cover [Zampieri et al., 2009]. Given the Neogene to Quaternary sinistral strike-slip kinematics superimposed on the fault system, the relay zone has accommodated along-strike local extension and may be responsible for rock fracturing and permeability development. The presence of a 5 meter-high hill of travertine in Abano Terme strongly supports the existence
67 of a releasing structure that controls 1) the outflow of thermal waters in the EGF and 2) ongoing activity of the SVFS that keeps open the fractures. The hill is affected by a network of fractures (mainly oriented WNW-ESE and NNE-SSW), which allow us to refer to the travertine deposit as a travertine fissure mound. The fracture network is interpreted as a fault/fracture mesh developing in a dilational stepover between strike-slip or transtensional fault segments of the SVFS. Geostatistical analyses on transmissivity of the thermal aquifer show a WNW-ESE anisotropy [Fabbri, 1997] that parallels the direction of fissures. A 3D model of the EGF subsurface and a cross section of the thermal circuit is constructed using seismic sections and the stratigraphy of deep wells (Villaverla 1 and Vicenza 1 in the northern part, Due Torri in Abano). The new conceptual model locates the thermal circuit east of the SVFS, instead of west like in the previous model. The meteoric waters infiltrate in an area 60 Km north of EGF thanks to the high secondary permeability of the outcropping rocks. They flow to the south inside a carbonate reservoir (mainly composed of the Dolomia Principale formation), which in the EGF is structurally displaced at depths between 2000 and 3000 m, and warm up by a normal geothermal gradient. The damage zone of the SVFS acts as a conduit for the hot waters, because of the higher permeability of the rocks than the protolith. In EGF area the local extensional regime keeps open the fractures and permits the quick rising of hot waters. A preliminary mathematical hydrothermal model of the EGF is developed using the software Hydrotherm [Kipp et al., 2008]. Hydrotherm simulates thermal energy transport in threedimensional, two-phase, hydrothermal, ground-water flow systems. REFERENCES Fabbri P. (1997) Transmissivity in the Euganean Getohermal Basin: a geostatistical analysis. Groundwater, 35(5), Kipp K.L. Jr., Hsieh P.A., Charlton S.R. (2008) Guide to the revised groundwater flow and heat transport simulator : HYDROTHERM - Version 3. U.S.G.S. Techniques and Methods, 6 A25, 160 pp Piccoli G., Bellati R., Binotti C. et alii (1976) Il sistema idrotermale euganeo-berico e la geologia dei Colli Euganei. Mem. Istituti Geol. Miner. Università di Padova, 30, 266 pp Zampieri D., Fabbri P., Pola M. (2009) Structural constrains to the Euganean Geothermal Field (NE Italy). Rendiconti online Società Geologica Italiana, 5, 238
68 Distributed temperature sensing behind casing Results from a flow test in a hot geothermal well Thomas Reinsch 1, Jan Henninges 1, Ragnar Ásmundsson 2 1 Helmholtz Centre Potsdam, German Research Centre for Geosciences GFZ, International Centre for Geothermal Research, Potsdam, Germany 2 ÍSOR - Iceland GeoSurvey, Reykjavík, Iceland PhD Student Wellbore integrity is an important issue for a sustainable provision of geothermal energy. This study reports on temperature data that have been acquired prior to a casing failure in the hot geothermal well HE53 within the Hellisheiði geothermal field, SW Iceland. A fiber optic cable has been installed behind casing and temperature data have been acquired using the distributed temperature sensing (DTS) technique. The temperature information will be used together with conventional logging data in order to study thermal processes during a flow test in summer In May 2009, the fiber optic cable has been installed behind the anchor casing of a geothermal well down to a depth of 261 m below ground surface. The well was completed by the end of June with a measured depth of 2400m. During the beginning of a flow test in August 2009, DTS measurements were performed for a period of two weeks. During this time, the wellhead temperature increased up to 240 C and maximum measured temperatures within the annulus behind the anchor casing rose up to 230 C. Although a steady increase in wellhead temperatures was observed, a short term decrease in temperature was detected within the annulus, locally (figure 1). Successively, decreasing temperatures were measured in shallower depth intervals. The temperature decrease migrated along the axis of the well with a velocity of approx m/h and lasted for a few hours within each depth interval. One hypothesis to explain the temperature depression might be the absorption of energy due to the vaporization of liquid. The large temperature increase within the well (>200 C) led to a rising vapor pressure of the pore fluid in the cemented annuls of the casing. Eventually, the vapor pressure was released and the fluid vaporized, absorbing energy. Within this study it should be examined if the absorption of energy might be an indication for the opening of small fractures within the cement. Due to the thermal expansion of the casing, pressure is applied to the cement. If the stress exceeded the strength of the cement, small
69 fractures could evolve. These fractures might have caused a reduction of the pressure within the cement, leading to the vaporization and thus to a reduction of the temperature. Figure 1 Temperature evolution within the annulus during the onset of the flow test. Temperatures in two different depths are displayed.
70 Influence of fault zones on fracture systems in sedimentary geothermal reservoir rocks in the North German Basin Dorothea Reyer, Sonja L. Philipp 1 Adress of 1st author (Geoscience Centre, Department of Structural Geology and Geodynamics, Georg-August Universität Göttingen, Germany) Educational level (Dipl.-Geow.) In the North German Basin many sedimentary rocks have low matrix porosities so that the increase of permeability due to fault zones can be exceedingly high. For different lithologies, such as sandstones and limestones, however, fault zones have dissimilar effects on the fracture systems therein. That is, the deformation of sandstone in a fault zone differs from that in limestone so that the changes of the fracture systems because of the fault zone development are others. Understanding this opposing behaviour is important to better assess the development and propagation of faults. This allows better evaluation and permeability estimates of potential fault-related geothermal reservoirs in sedimentary rocks of the western North German Basin. Fault zones commonly consist of two mechanical units: the fault core and the damage zone. The fault core is composed of brecciated material and usually has a small permeability, when the fault is not active (slipping). In contrast, in the damage zone, the mechanically stressed area, the fracture density normally increases and therefore the permeability is higher than in the host rock (fig. 1). Figure 1: Fault zone structure and typical distribution of fracture density and permeability. The fault core permeability dependst on the fault zone activity (mod. Caine et al. 1993). Here we present results of structural geological field studies on the geometry and architecture of 51 outcrop-scale fault zones of various types in sedimentary rocks of the western North German Basin. We measured their orientations and displacements, the thicknesses of their fault cores and damage zones, as well as the fracture densities and geometric parameters of the fracture systems therein. Our field studies show that in sandstones and limestones especially the damage zones are built-up differently. Particularly in limestones, fractures associated with
71 fault zone development are numerous so that the fracture densities in the damage zones are high. In sandstones the effects of the fault zones on the fracture systems are much lower (fig. 2). Therefore we discuss the fault-zone caused changes in the damage zones of fracture densities, orientations, openings and lengths compared with the host-rock fracture systems separately for sandstones and limestones. The data indicate that fault zones have greater effects on the fracture systems in limestones than in sandstones. This is manifest in a larger increase of the fracture densities (fig. 2), fracture openings as well as the fracture lengths in limestone damage zones. The damage zone widths compared with the displacements are also higher than in sandstones. For limestones it seems that there is also a relation between the fault damage zone width and the orientation of the fault zone associated to regional fault structures. Small faults with parallel orientation to the major regional fault system appear to develop wider damage zones than those with a high angle to the major fault system. a) b) Figure 2: Fracture density distribution for two slightly faulted outcrops; a) Two normal faults in a sandstone profile (Solling-formation of the Middle Bunter), b) two normal faults in a limestone profile (Wellenkalk 1, Lower Muschelkalk). The shaded box represents a strongly damaged part of the profile, not all fractures could be measured. The results indicate that the positive effects of fault zones on fracture density and permeability are more pronounced in limestones than in sandstones (fig. 2). Our results, however, do not yet allow general and final statements on the geothermal potential of faultassociated geothermal reservoirs in limestones or sandstones. Nonetheless structural geological field studies of fault zones in outcrop analogues help to improve our knowledge of fault-zone evolution and structure. To improve permeability estimates of a fault-associated geothermal reservoir in a specific stratigraphy and lithology it is necessary to perform further field studies in outcrop analogues of the geothermal reservoir rocks in question.
72 Water-rock interaction of silicic rocks under geothermal conditions: An experimental and modelling study Alejandro Rodríguez*, Andri Stefánsson Department of Earth Sciences, University of Iceland, Sturlugata 7, 101 Reykjavík, Iceland * MSc student, contact: Water-rock interaction may be affected by various processes including temperature, rock composition and crystallinity, acid supply and extent of reaction. In this study the effect of extent of reaction on the interaction of silicic rocks under geothermal conditions was investigated both experimentally and by geochemical modelling. Two volcanic glasses from Iceland were used in the experiments, dacite from Askja volcano (A75) and rhyolite from Hekla (H3W). The glassy rocks were reacted with water containing NaCl, H 2 S and CO 2 in a close system at 240 C for up to 94 days. Liquid samples were collected regularly and solid samples at the end of the experimental runs. Major elements analyzed in the water samples included CO 2, H 2 S, F, Cl, Na, K, Ca, Mg, B, SO 4, Si, Fe, Ti and Al and secondary mineralogy was identified using XRD and SEM analysis. The reaction path was further simulated and compared with the experimental results with the aid of the PHREEQC computer program (Parkhurst and Appelo, 1999) in order to get insight into the progressive water-rock interaction at fixed temperature and system composition. Different trends were observed as a function of reaction time. Titanium, Mg, Fe, Na, SO 4, and CO 2 concentrations in the water decreased, H 2 S remained almost constant, Si initially increased followed by decrease after several days, Al decreased and subsequently increased whereas Ca and K concentrations increased as a function of reaction time. The secondary minerals identified unambiguously so far include quartz and amorphous SiO 2, Nasmectite, analcime, calcite and albite. The experimental results and geochemical model calculations indicate that the process of alteration of silicic rocks at fixed temperature and composition is incongruent and affected by reaction progress (Fig 1). The water samples were saturated throughout the experiment with respect to microcline, calcite, pyrite and rutile whereas analcime, Na-montmorillonite were initially saturated but became undersaturation with reaction time. Quartz and albite were initially supersaturated reaching equilibrium saturation after >60 days. This trend is in line with the reaction path modelling, with clays, zeolites, pyrite, and anatase forming at low reaction progress and chlorite, quartz, calcite and eventually fluorite and illite with increased silicic rock dissolution.
73 Illite Moles of secondary minerals formed Fluorite Pyrite ph The effect of extend of reaction on water-rock interaction implies that equilibrium assumptions between secondary minerals and fluids is not only fixed by temperature for a closed system of fixed composition. Reaction progress is also important. For example, the calculated Na/K and quartz geothermometry temperatures from the experimental results, resulted experimental temperatures only after days of reaction, whereas higher temperatures were initially obtained. 106 g of Askja 1875 glass in 1 kg of water (1000 steps) Quartz Analcime E-005 ph Montorillonite Na Anatase Chamosite 7-A Clinochlore 14-A Calcite Analcime Quartz Calcite Clinochlore 14-A ph Pyrite Anatase Chamosite 7-A Montmorillonite Na Flourite Illite 1E-006 1E Reaction progress (mole rock/kg water)) Fig. 1. Reaction path modelling of 106 g of A75 glass in 1 kg of water.
74 3D inversion of geophysical data for Geothermal exploration Gudni Karl Rosenkjaer 1,2 1Department of Earth and Ocean Sciences, University of British Columbia, Canada 2Geophysics Department, Iceland Geosurvey, Iceland contact of the summer school participant for future correspondance Educational level (Phd) The Transient Electro-Magnetic (TEM) and MagnetoTelluric (MT) sounding methods are commonly used in geothermal exploration. The subsurface resistivity models interpreted from these measurements have proven to have correlation with geothermal system properties such as hydrothermal alteration, temperature and permeability. Resistivity models are valuable in research of geothermal system and joint interpretation with other data such as geology, geochemistry and other geophysical data provides a conceptual understand of the system. A widely used procedure during interpretation of Electro-Magnetic data is to use inversion modelling. Knowing how Electro-Magnetic waves travel thought conductive materials, allows predicted data to be calculated for a conductivity model of the earth in the vicinity of the measurements. Computer codes are used to find an optimal model that explains the measured data to certain accuracy. The inversion can be done in 1-, 2- or 3-dimensions, where the complexity and time to solve the inversion problem increases with higher dimensions but the approximation of the earth becomes more realistic. Due to no-uniqueness in the inversion problem, constraints are need for the inversion to find the best model that explains the data. Other important issues arise, such as pre-processing of the data, error estimation and selection of appropriate constrains. In the project Electro-Magnetic and other geophysical data from the Hengill and Krafla geothermal areas in Iceland will be subject to advanced joint inversion. Previously collected TEM and MT data from these areas will be inverted to produce detailed 3 dimensional model for the conductivity. The next step will be to combine 3D seismic tomography and resistivity inversion. The joint inversion will not be based on parametric relations between resistivity and sound velocity, but rather as a geometric inversion, looking for coincident anomalies in the two physical parameters.
75 Density and Viscosity Effect on Heat Transfer in Porous Media: Sanaz Saeid - CITG Producing energy from geothermal reservoirs becomes opportune as a new sustainable energy source. Hence, insight is required in the heat balance of potential aquifer systems. Essential issues are convection, conduction and dispersion. During the process of heat transfer in such aquifers there are some details which should be taken in the account to be abele to optimize the production of the system. Two of these aspects are density and viscosity. Injection back of cold water in the hot reservoir will change aquifer s temperature and consequently its density and viscosity in time, which affect pressure distribution significantly. Due to this fact the discharge won t be constant in time. A model test which has been prepared to quantify these effects shows differences up to 150%.
76 Tectonic and structural control on geothermal fields of the Biga Peninsula, Northeastern Aegean Matias Sanchez Schneider (MSc. PhD student); Professor Ken McClay Department of Earth Sciences, Royal Holloway University of London Egham Hill, Egham, Surrey, TW20 0EX, UK Abstract Extensional fault related zones are characterized by high density fracturing and faulting. These structures are particularly abundant along the fault hangingwalls in the vicinity of major fault tips and fault linkage zones. Damage zones respond to the loading and unloading cycles of stress concentrations during seismic slip on crustal fault systems. The North-eastern Aegean is dominated by back-arc extension and dextral transtension leading to a thinned continental crust of high geothermal gradients. Pervasive faulting has significantly increased rock permeabilities, enhanced fluid flow and pressure gradients in the region, and therefore has favoured the generation of hydrothermal precipitation and occurrence of geothermal fields. The formers appear in particular controlled by fault/fracture architectures along the vicinity of granitic plutons and aplitic dike swarms. This research presents the results of a multidisciplinary study that used remote sensing satellite imagery, magnetic data, geological mapping, structural analysis, isotopic dating, well log data and rock geochemical data; as well as numerical and analogue modelling. These techniques were used to develop 4D evolutionary models for the fracture patterns and distributions around the segmented fault systems of the Biga peninsula, western Turkey. In this way, determination of the magnitudes and types of stresses that occurred along each segment of the extensional fault systems has allowed the development of 4D models for the formation of the fault zone fracture architectures. These fracture systems may be receptive or hostile to geothermal fields due to their capacity to act as conduits or traps for fluid flow.
77 Discrete Fracture Matrix (DFM) models for modelling heat and mass transfer in geothermal reservoirs. T.H. Sandve _ I. Berre _y J.M.Nordbotten _z January 31, 2011 Understanding ow in fractured reservoirs is crucial for developing geother- mal resources. Reservoir models with improved qualitative and quantitative pre- dictive capabilities are important to aid planning and decision making; however, the range of active scales involved and the geological complexity of fractured porous medium is a challenge in developing mathematical models and numerical solution strategies. In our approach, we consider a control volume discretization along with multi-point-ux approximations, which allows for anisotropic con- ductivities on challenging grids. We explicitly account for dominating fractures, allowing for fracture elements that are several orders of magnitudes smaller than the matrix elements. Inspired by an approach recently introduced for a two-point-ux approximations, elements in the intersection of fractures are elim- inated through a star-delta transformation; hence, avoiding associated time-step restrictions. Numerical results demonstrates the exibility and robustness of the new approach. _Department of Applied Mathematics, University of Bergen, 5008 Bergen, Norway ychristian Michelsen Research, Norway zprinceton University, USA
78 Gas Chemistry of the Hellisheiði Geothermal Field Samuel Scott 1, Ingvi Gunnarsson 3, Andri Stefánsson 2, Stefán Arnórsson 2, Einar Gunnlaugsson 3 1 Reykjavík Energy Graduate School of Sustainable Systems, Baejarhalsi 1, 110 Reykjavík, Iceland 2 University of Iceland, Institute of Earth Science, Sturlugata 7, 101 Reykjavík, Iceland 3 Reykjavík Energy, Baejarhalsi 1, 110 Reykjavík, Iceland MSc A fluid sampling campaign has recently been carried out at the Hellisheiði geothermal field in southwest Iceland. This high-temperature field is a subfield of a large volcanic hydrothermal system associated with the Hengill central volcano, and is host to the largest geothermal power plant in Iceland. A geochemical assessment of the field is presented based on the analysis of 19 wet-steam well discharges. Emphasis is placed on the chemical and physical processes that account for the concentrations of the major reactive gases (CO 2, H 2 S, H 2 and CH 4 ). Aquifer chemical compositions were calculated from analysis of discharged water- and steam-phases and discharge enthalpies using the WATCH speciation program and phase segregation model. Under this model, discharge enthalpies in excess of that of vapor saturated liquid at the aquifer temperature are accounted for by retention of liquid in the formation at a single pressure. The calculated concentrations of volatile components in initial aquifer fluids are observed to be very sensitive to the selected phase segregation pressure, while calculated non-volatile concentrations are fairly insensitive. Investigation of mineral-solution equilibria reveals approach a close approach to saturation with respect to main hydrothermal alteration minerals. Systematic disequilibrium is observed with respect to gas-gas redox reactions, confirming past studies of dilute Icelandic hydrothermal fluids. Carbon dioxide concentrations are kept in close equilibrium with calcite. The concentrations of H 2 S and H 2 species show a close approach to equilibrium with a mineral assemblage consisting of pyrite, pyrrhotite, epidote and prehnite. The field-scale distributions of the main geothermal gases are used constrain the locations of two separate upflow zones identified within the geothermal area. Additionally, chloride and nitrogen suggest the presence of a recharge zone in the northern part of the geothermal field directed towards the south. This information should be taken into consideration in future conceptual models for the Hengill area.
79 Petrophysical characteristics of sandstones dating from the Buntsandstein in the Upper Rhine Graben: case of the borehole EPS1 (Soultz-Sous-Forêts, France) HAFFEN Sébastien 1, GERAUD Yves 1, DIRAISON Marc 1, DEZAYES Chrystel 2 1 1, rue Blessig Strasbourg (EOST Université de Strasbourg, France) 2 BRGM Dpt Geothermal Energy Orleans, France PhD This study is based on petrophysical analyses of sandstones from the Upper Rhine Graben, between France and Germany. These sandstones dating from the Buntsandstein (lower Trias) appears to be an easy target for geothermal exploitation, linking sandstone and clay with the regional thermal anomaly. This sedimentary series is composed by different lithostratigraphic levels with coarse and fine grains or conglomerate with high content of clay at the base and the top of the series. Completely cored between 1008 to 1417 m depth, the borehole EPS1, located in Soultz-Sous-Forêts, offers a continuous cut of the sedimentary series. High resolution petrophysical measurements have been performed on these cores and enable us to characterize the different sedimentary facies properties of the Buntsandstein sandstones. These measurements drive us to analyze thermal conductivity, permeability and porosity at different scales: from milimetric to hectometric. Porosities determined by mercury injection show variations between 1 and 21 % without tendency with depth. Permeabilities vary between 0.33 and 512 md. In the Vosgien sandstone, three zones appears with higher permeabilities values and are reliable with sedimentary facies: 1) Playa-lake and fluvial and Aeolian sand-sheet 2) Fluvial-Aeolian marginal erg 3) Braided rivers within arid alluvial plain but only in the basal section where the layers are thick. The upper and the lower parts appear with low porosities and permeabilities. A complete profile of thermal conductivity on dry cores show low values (2.5 W/m/K) in the upper and lower part of the borehole. Measurements performed in the playalake facies indicated the higher heterogeneities with values comprise between 1 and 10 W/m/K. Measurements are also performed too on wet samples (78) and compared with geometrical mixing law from mineralogical XRD determination. Thermal conductivity maps made on dry and wet decimetric samples permit to build relative porosity map. Porosity increase around fractured zones and a drastic decrease of porosity is observed near barite precipitation areas.
80 Quantification of geochemical energy in geothermal ecosystems Ásgerður K. Sigurðardóttir 1, Andri Stefánsson 1, Guðmundur Óli Hreggviðsson 2, Snædís Björnsdóttir 2 and Sólveig Pétursdóttir 2 1 Department of Earth Science, University of Iceland, Sturlugata 7, 101 Reykjavik, Iceland 2 Matis ohf, Vínlandsleið 12, 113 Reykjavík, Iceland MSc student Many geothermal ecosystems utilize geochemical energy for metabolic reactions. The magnitude of chemical energy available to microbial communities in geothermal water may be assessed by combining thermodynamic calculations with analytical techniques used for direct dissolved species determination. This approach allows for the quantification and ranking of various potential sources of inorganic chemical energy that may support microbial life. In order to quantify such source of energy in Icelandic surface geothermal waters, samples were collected from five different geothermal areas including Geysir, Flúðir, Ölkelduháls, Reykholtsdalur, Torfajökull. The major and trace elements were analysed as well as direct speciation determination of N (NH 4, NO 2, NO 3 ), S (H 2 S, S 2 O 3, SO 4 ), H 2 O (O 2, H 2, H + ), and C (CH 4, CO 2 ) using combination of titrations, ion chromatography and colorimetric techniques. The ph of the water and the temperature range were 3-9 and C, respectively. Combined with thermodynamic calculations of the appropriate redox reactions, the non-equilibrium excess energies (chemical affinities, A r ) defined as, were calculated for over 100 reactions and these ranked according to their importance as an energy source. To determine the chemical affinity of a particular reaction, the equilibrium constant were calculated using the Supcrt92 program and slop07.dat database (Johnson et al., 1992) and the reaction quotient,, were calculated from the measured spcecies concentrations and calculated activity coefficients from total water composition using the PHREEQC program (Parkhurst and Appelo, 1999). Examples of the results are shown in Figure 1 for reactions involving sulphur species. The reactions yielding the highest energy involved oxidation or reduction of S (s) and S 2 O 2-3 by O 2 and H 2, respecitively. Other reactions of importance involved oxidation or reduction of S (s) and SO , H 2 S and SO 4 and S 2 O 3 and SO 2-4. The overall trend was found to be relatively insensitive to ph and temperature and whether the reaction was written as oxidation
81 or reduction reaction. The energies thus obtained may be compared with known metabolisms of the geothermal ecosystems in order to identify the chemical reactions of importance for chemotrophic microbiological communities. 20 H + to H 2 (aq) and O 2 (aq) to H 2 O and... Chemical affinity (kcal/mol e - ) H 2 S to S(s) H 2 S to S 2 O 3 H 2 S to SO 4 S(s) to S 2 O 3 S(s) to SO 4 S 2 O 3 to SO 4 H 2 S to pyrite pyrite to S(s) pyrite to S 2 O 3 pyrite to SO 4 Chemical affinity (kcal/mol e - ) H 2 S to S(s) H 2 S to S 2 O 3 H 2 S to SO 4 S(s) to S 2 O 3 S(s) to SO 4 S 2 O 3 to SO 4 H 2 S to pyrite pyrite to S(s) pyrite to S 2 O 3 pyrite to SO ph ph Fig. 1. The calculated chemical affinity (A r ) of reactions involving various sulphur species as a function of ph. The reactions yielding the highest positive chemical affinity are the reactions releasing most energy for possible metabolism.
82 Thermal and Structural Analysis of the Production Casing in a High Temperature Geothermal Well Gunnar Skúlason Kaldal 1 *, Magnús Þ. Jónsson 1, Halldór Pálsson 1, Sigrún N. Karlsdóttir 2, Ingólfur Ö. Þorbjörnsson 2,3 1 Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, University of Iceland, Hjarðarhagi 2-6, Reykjavik, 107, Iceland 2 Innovation Center Iceland, Department of Materials, Biotechnology and Energy, Keldnaholt, Reykjavik, 112, Iceland 3 Reykjavik University, Menntavegur 1, Reykjavik, 101, Iceland * MSc (PhD student) The production casing of a high temperature geothermal well is subjected to multiple thermomechanical loads in the period from installation to production. Temperature and pressure fluctuations are large in high temperature geothermal wells, for example during the first discharge the temperature difference from a non-flowing to a flowing well can be on the range of hundreds of degrees centigrade. During installation, stimulation and production, problems can arise due to these loads and due to a possible corrosive geothermal environment. Plastic buckling of the production casing is a problem that can occur. It results in a bulge in the wall of the casing and is detrimental to the geothermal energy production and the lifetime of the well. The cost of each well is very high. Therefore, it is important to analyze the structural environment of high temperature geothermal wells in effort to avoid repeated problems in the design and installment phases of the casing. A finite-element model has been developed to evaluate the temperature distribution, deformation and stresses in a high temperature geothermal well and to evaluate the reasons for buckling in the production casing. The load history of the casing is followed from the beginning of the installment phase to the production phase. The results show that the load history and also the sequence of loading is important in order to understand the true structural behavior of wells.
83 Evaluation of suitable working fluids for single ORC by the concept of power maximization C. Steins 1, M. Habermehl 1 & R. Kneer 1 1Institute of Heat and Mass Transfer, RWTH Aachen University, Eilfschornsteinstraße 18, Aachen, Germany Dipl.-Ing. The use of geothermal energy for power generation at brine temperatures of less than 200 C is achieved by a binary process, especially by the Organic-Rankine-Cycle (ORC). Thereby, the choice of a suitable fluid results in another level of complexity in the design of such a process. The study analyses criteria for the evaluation of an ORC related to a given brine flow. Due to the given temperature and the given heat capacity rate, the aim for ORC design is to maximize the power output. Since the heat flow and the heat capacity rate from the geothermal source are limited, a simple efficiency consideration for the ORC based only on the Carnot efficiency will not lead to the maximum power output. The heat transfer between the brine and the working fluid must also be included into efficiency considerations. Using the concept of power maximization to characterise the process temperatures, the choice of the fluid is used as a design parameter to optimise the heat transfer into the ORC. It is shown how the choice of the fluid influences the power output and the ability of the ORC to transfer the brine s heat into work. Furthermore, considerations for a consistent efficiency definition are presented. Based on a preliminary developed theoretical concept, the study analyses eight different working fluids, which have been chosen by their thermodynamic properties in relation to the maximum temperature of the brine. Within under-critical conditions the simple power cycle is then calculated over an interval of process power. As a reference, the conditions for a prospected geothermal power station in the German Upper Rhine Graben are taken (brine temperature of 150 C, brine mass flow of 100kg/s, condensing temperature of 30 C). To evaluate the parametric study with respect to net power output, thermal and exergetic efficiency, the efficiency itself is moreover analysed and defined to the very specific conditions of a geothermal power station. The results of the calculations generally agree with the theoretical idea of the concept, but also show a very depending behaviour, which is the source for new conclusions. Especially, the points of maximum power output and maximum efficiency are not necessarily connected. Rather, the influence of the working fluid is very large (compare Fig. 1 as an example).
84 The study gives not only the reason for the differences between the single working fluids and which properties are crucial for best performance considerations, but also it shows the possibility to identify the point of maximum power by the concept of power maximisation 1. 1 A. Bejan. Entropy Generation Minimization The Method of Thermodynamic Optimization of Finite-Size Systems and Finite-Time Processes. CRC Press, 1996.
85 Thermal configuration and homeothermal surface of shallow aquifer in Piemonte plain (NW Italy) Marco STRINGARI 1 Riccardo BALSOTTI 2 Domenico Antonio DE LUCA 3 1 Earth Science Department, University of Torino, Italy 2 Coordination of regional activities on the environment and water quality, ARPA Piemonte, Italy 3 Earth Science Department, University of Torino, Italy Educational level: Phd student The knowledge of temperature of groundwater is important for the exploitation of subsoil by means of low enthalpy geothermal plants. The temperature of groundwater can be considered as the starting condition on which thermal disturbance induced by a geothermal heat exchanger may have effect. An extensive research project started in 2008, with the aim of characterizing geothermal aptitude of Piemonte plain (NW Italy) and the impact of geothermal heat exchangers on the ground. A study was carried out in order to evaluate the temperatures of shallow aquifer in Piemonte plain. Two piezometric and thermometric surveys was conducted (in spring and autumn of 2008) in the regional piezometric monitoring network. In particular temperature logs of water column were performed. The main purpose of the survey was to verify and quantify the lateral and local variations of temperature in shallow aquifer and the presence of any temperature gradient with increasing depth. Maps of autumn and spring average temperatures were made by interpolating average temperatures in each piezometer. A comparison was made between the thermal conditions in each piezometer and a homeothermal surface was identified. Maps of homeothermal surface in relation to ground level and to groundwater level were realized. The obtained results aspire to define the thermal configuration of the shallow aquifer in Piemonte plain, according to a growing demand for installation of geothermal plants and information about the thermal characteristics of the aquifers.
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