2nd European Geothermal PhD...

2nd European Geothermal PhD Day

2nd of March 2011

Reykjavík, Iceland

Collection of Abstracts

We are grateful to our sponsors:

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, hydro-

power 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

www.president.is, 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.

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 2011.

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, www.geothermal.is/phd-day.

We would like to thank all the participants of the EGPD 2011. 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

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

10:30-11:00 Coffee Break



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)


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

Participants

First Name Last Name E-Mail Institution / Facility

1 Edda Sif Aradóttir [email protected] University of Iceland and Reykjavík Energy

2 Márton Barcza [email protected] University of Szeged (Hungary)

3 Thomas Benson [email protected] Stanford University/Massachusetts Institute of Technology

4 Björn Bjartmarsson [email protected] School for Renwable Energy and Dept. Of Mechanical and Industrial Engineering, University of Iceland,

5 Héðinn Björnsson [email protected] University of Iceland/Iceland Geosurvey

6 Damien Bonté [email protected] Vrije Universiteit Amsterdam, FALW, Tectonic group

7 Olga Borozdina [email protected] GPC Instrumentation Process (GPC IP)

8 Maren Brehme [email protected] Helmholtz Centre Potsdam - German Research Centre for Geosciences (GFZ), International Centre for Geothermal Research

9 José Estévez [email protected] University of Iceland / UNU-GTP

10 Sara Focaccia [email protected] DICAM- University of Bologna

11 Laura Foulquier [email protected] GPC Instrumentation Process (GPC IP)

12 Henning Francke [email protected] GFZ Potsdam

13 Iwona Galeczka [email protected] University of Iceland / Institute of Earth Sciences

14 Iska Gedzius [email protected] Insitute of Peroleum Engineering (Clausthal University of Technology)

15 Snorri Guðbrandsson [email protected] University of Iceland / Institute of Earth Sciences

16 Maria Gudjonsdottir [email protected] Reykjavik University / School of Science and Engineering

17 Egill Árni Guðnason [email protected] ÍSOR / University of Iceland

18 Sveinborg Hlíf

Gunnarsdóttir [email protected] University of Iceland / ISOR

19 Helga Margrét

Helgadóttir [email protected] ÍSOR/University of Iceland

20 Heimir Hjartarson [email protected] Faculty of Industrial Engineering, Mechanical Engineering and Computer Science

21 Henrik Holmberg [email protected] Dept of Energy and Process Engineering, NTNU

22 Saqib Javed [email protected] Building Services Engineering, Chalmers University of Technology

23 Hanna Kaasalainen [email protected] University of Iceland/Nordic Volcanological Center

24 Marta Rós Karlsdóttir [email protected] University of Iceland / Department of Industrial Engineering, Mechanical Engineering and Computer Sciences

25 Evgenia Kontoleontos [email protected] National Technical University of Athens /School of Mechanical Engineering

26 Éva Kun [email protected] Szeged University

27 Heiko Liebel [email protected] Norwegian University of Science and Technology

28 Magnus Bjørnsen

Løberg [email protected] University of Bergen

29 Mary Luchko [email protected] Moscow State University

30 Kiflom G. Mesfin [email protected] University of Iceland / Institute of Earth Sciences

31 Helena Nakos [email protected] Chalmers University of Technology

32 Steinþór Níelsson [email protected] University of Iceland / Iceland GeoSurvey

33 Mochamad Nukman [email protected] GFZ - Potsdam

34 Yodha Yudhistra

Nusiaputra [email protected] IKET, Karlsruhe Institute of Technology (KIT)

35 Pacifica F. Achieng

Ogola [email protected] UNUGTP / University of Iceland

36 Auður Agla Óladóttir [email protected] ÍSOR, Háskóli íslands

37 Snjolaug Olafsdottir [email protected] University of Iceland, Faculty of Civil and Environmental Engineering

38 Jonas Olsson [email protected] University of Iceland / Institute of Earth Sciences

39 Kevin Padilla [email protected] Faculty of Earth Sciences, University of Iceland

40 Marco Pola [email protected] Dipartimento di Geoscienze – Università degli Studi di Padova

41 Thomas Reinsch [email protected] Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences

42 Dorothea Reyer [email protected]

Geoscience Centre, University of Göttingen

43 Alejandro Rodríguez [email protected] University of Iceland / Institute of Earth Sciences

44 Guðni Karl Rosenkjær [email protected] University of British Columbia/Iceland Geosurvey

45 Uwera Rutagarama [email protected] University of Iceland/United Nations Geothermal Training program

46 Sanaz Saeid [email protected] Technical university of Delft

47 Matias Sanchez Schneider [email protected] Royal Holloway, University of London

48 Tor Harald Sandve [email protected] Department of Mathematics, University of Bergen

49 Samuel Scott [email protected] Reykjavik Energy Graduate School of Sustainable Systems (REYST), University of Iceland

50 Haffen Sébastien [email protected] EOST – University of Strasbourg

51 Ásgerður Kristrún

Sigurðardóttir [email protected] University of Iceland / Institute of Earth Sciences

52 Gunnar Skúlason Kaldal [email protected] University of Iceland

53 Sandra Snaebjornsdottir [email protected] University of Iceland / Iceland GeoSurvey

54 Christopher Steins [email protected] RWTH Aachen University, Institute of Heat and Mass Transfer

55 Marco Stringari [email protected] University of Torino (Italy)

56 Christian Vetter [email protected] Karlsruhe Insitute of Technology (KIT)

57 Esther Vogt [email protected] Leibniz-Intitut for Applied Geophysics

58 LiWah Wong [email protected] GFZ German Research Centre for Geosciences

Abstracts

Reactive transport models for mineral CO2

sequestration in basaltic rocks

Edda S.P. Aradottir1,2,*

, Eric Sonnenthal3, Grimur Bjornsson

4, Hannes Jonsson

1

1Science Institute of the University of Iceland, VR-III, 107 Reykjavik, Iceland

2Reykjavik Energy, Baejarhalsi 1, IS-110, Reykjavik, Iceland

3Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley CA 94720, USA

4Reykjavik Geothermal, Kollunarklettsvegi 1, IS-104, Reykjavik, Iceland

*[email protected]

Educational level: Ph.D.

Reacting CO2 with basalt to form thermodynamically stable carbon-rich minerals may provide

a long lasting, thermodynamically stable and environmentally benign solution to reduce

anthropogenic CO2 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 CO2 of volcanic origin will be dissolved in

water and injected at intermediate depths (400-800 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 CO2 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 CO2 into basalts.

Natural analogs of CO2-water-basalt interactions provide important insight into the secondary

mineralogy associated with the CarbFix CO2 injection, and hence which minerals are likely to

compete with carbonates for dissolved cations. Secondary minerals of CO2 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 2007. 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 CO2 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, pCO2 and flow rate. Optimally, simulations with the CarbFix field model

should determine which injection scenario will maximize mineralization of injected CO2 as

well as to show the depth and temperature range best suited for the mineralization.

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 Allow1 – Sándor Kiss 1 –

Tibor Jánosi Mózes 1

1 Department of Mineralogy Geochemistry and Petrology, University of Szeged, Hungary

[email protected] 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.

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.

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 - 200 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.

Constraining Reservoir Models with Surface Measurements

Héðinn Björnsson1

1Natural Science, University of Iceland, Iceland

[email protected] (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.

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. [email protected]

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 0.0485. 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 0.2555, 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.

Figure 1: User generated data, 1-tank model with +/- 5% random noise

Figure 2: Bjarnarflag well BJ-11 simulated with a 1-tank model

New temperatures for the Paris Basin

Results from tectonic-Heat Flow modelling

Damien Bonté1, Jan Diederik Van Wees

1-2, Laurent Guillou-Frottier

3, Vincent Bouchot

3, Olivier

Serrano3

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, 45060 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 present-

day 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).

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.,

2010. Subsurface temperature maps in French sedimentary basins: new data compilation and

interpolation. Bulletin de la Société Géologique de France, 181, 375-388.

Guillocheau F., Robin C., Allemand P., Bourquin S., Brault N., Dromart G., Friedenberg R.,

Garcia J.P., Gaulier J.M., Gaumet F. & al., 2000. Meso-Cenozoic geodynamic evolution of the

Paris Basin: 3D stratigraphic constraints. Geodinamica Acta, 13, 189–246.

Van Wees J.D., Van Bergen F., David P., Nepveu M., Beekman F., Cloetingh S. & Bonté D.,

2009. Probabilistic tectonic heat flow modeling for basin maturation: Assessment method and

applications. Marine and Petroleum Geology, 26, 536-551.

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.

The integrated view on a geothermal reservoir

Maren Brehme1, 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, 14473 Potsdam, Germany

2 Pertamina Geothermal Energy, Skyline Building, MH. Thamrin No.9, Jakarta 10340, Indonesia

[email protected]

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 GWe. 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 HCO3-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 SO4- 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 HCO3-concentrations the samples plot on the line between Cl and SO4 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 water-

mixing 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.

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, 2749-2765

Geostatistical modeling of natural mean‘s properties for flux simulation through

FEM,FDM codes: analysis of Thermal Response Test data

Sara Focaccia1, Roberto Bruno

2, Francesco Tinti

2

1,2 DICAM- University of Bologna, Italy

[email protected]

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 conductivity-

and borehole thermal resistance-Rb), 2 of them (initial time-ti and final time-tf) 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 tf estimates, a new

monovariate regression on the original data allows for the identification of the theoretical

Rb. Then, the methodology requires the user to

propose a guess probability distribution function for both variables. Once available, the

identification of

Fig. 2

- Validity area of Rb- b equation

-Rb relationship is found. And

finally the conditional expectation allows for identifying the correct and optimal couple of the

-Rb estimated values.

Two-phase flow in the brine circuit of a geothermal plant

Hennin Francke

Helmholtz-Zentrum Potsdam, Deutsches GeoForschungsZentrum - GFZ

Telegrafenberg, D-14473 Potsdam

[email protected]

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. N2, CH4, CO2). 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 CO2, 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

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.

Experimental studies on CO2 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 CO2 storage. Conceptual

model of CO2 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

Ca2+

, Mg2+

and Fe2+

. As reactions progress, these elements will combine with CO32-

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 CO2 injection, gives an opportunity to study the

rate of basaltic material dissolution and solid replacement reactions under controlled CO2 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 CO2 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 dm3. The column will be

filled up with basaltic glass grains, 45 to100 µm in size, of known chemical composition and surface

characteristic. CO2 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 CO2 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.

*e-mail: [email protected]

Optimum geothermal well constructions to maximize the heat output and

minimize costs

Ms. Dipl.-Ing. Iska Gedzius1, Dr. Dr.-Ing. C. Teodoriu

1, Prof. Dr.-Ing. K. M. Reinicke

1

1Adress of authors: Institute of Petroleum Engineering, Agricolastraße 10, 38678 Clausthal-Zellerfeld, Clausthal

University of Technology, Germany

Email contact of the summer school participant for future correspondence: [email protected]

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 5.000 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 1.000 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 the

circulation system.

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 this

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 for

geothermal energy exploitation is known. Figure 1 shows the

Figure 1: One-Well-Concept as

an open system

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

CO2 Mineralization into Basaltic Formations at the Hellisheiði Geothermal

Field – The CarbFix Project

Snorri Gudbrandsson1, Helgi A. Alfredsson

2 and Sigurdur R. Gíslason

3

[email protected], PhD student at the Institute of Earth Sciences, University of Iceland, Askja – Sturlugata 7, IS-

101 Reykjavík, Iceland [email protected], PhD student at the Institute of Earth Sciences, University of Iceland, Askja – Sturlugata 7, IS-101

Reykjavík, Iceland [email protected], Research Professor at the Institute of Earth Sciences, University of Iceland, Askja –

Sturlugata 7, IS-101 Reykjavík, Iceland

The reduction of industrial CO2 emissions is one of the main challenges of this century.

Among commonly proposed CO2 storage techniques, the injection of anthropogenic CO2 into

deep geologic formations is quite promising. One way to enhance the long-term stability of

injected CO2 is through the formation of carbonate minerals. Carbonate minerals provide a

long lasting, thermodynamically stable and environmentally benign carbon storage host.

Mineral carbonation of CO2 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

CO2 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 CO2 charged

waters into basaltic rocks, laboratory based experiments, study of natural CO2 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.

Properties of Two Phase Flow of Water and Steam in Geothermal

Reservoirs

Maria Gudjonsdottir1, Jonas Eliasson2, Halldor Palsson3, Gudrun Saevarsdottir4

[email protected], Ph.D. Candidate, School of Science and Engineering, Reykjavik University, Menntavegur 1, 101

Reykjavik Iceland [email protected], Prof. Emeritus, Faculty of Civil and Environmental Sciences, VRII, Hjardarhagi 2-

6, 107 Reykjavík, Iceland [email protected], Assoc. Professor, Faculty of Industrial-, Mechanical Engineering and Computer Science, VRII,

Hjardarhagi 2-6, 107 Reykjavík, Iceland [email protected], 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).

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, 1980. “Two phase flow in porous media and the

concept of relative permeabilities”. Proc. 6th

Workshop on Geothermal Reservoir Engineering

Dec. 16.-18., 1980 Stanford Geothermal Program.

Mahiya, G.F. 1999. “Experimental Measurement of Steam-Water Relative Permeability”.

M.Sc. Thesis, Stanford University, Stanford. CA.

Piquemal, J. 1994. “Saturated Steam Relative Permeabilities of Unconsolidated Porous

Media”. Transport in Porous Media, Vol. 17, pp 105-120.

Satik, C. 1998. “A Measurement of Steam-Water Relative Permeability”. Proceedings.

Twenty-Third Workshop on Geothermal Reservoir Engineering, Stanford University,

Stanford, CA.

Verma, A.K. 1986. “Effects of Phase Transformation of Steam-Water Relative

Permeabilities”. Earth Sciences Division Lawrence Berkeley Laboratory. University of

California Berkeley, CA.

The GEISER project

Egill Árni Guðnason1

Mr. Kristján Ágústsson, Dr. Ólafur G. Flóvenz2

1University of Iceland / Iceland Geosurvey, Geophysics, Iceland

2Iceland 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.

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 km2. 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

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, 1998.

Franzson, H., R. Zierenberg and P. Schiffman, 2008. ʺChemical transport in geothermal systems in Iceland.

Evidence from hydrothermal alterationʺ. Journal of Volcanology and Geothermal Research 173, 2008: 217-229.

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, 25-29 April 2010.

Kristmannsdóttir, Hrefna, 1979. ʺAlteration of basaltic rocks by hydrothermal activity at 100-300°C.ʺ

Developments in sedimentology (27), 1979: 259-367.

Simulation of Steam Separators using Smoothed Particles Hydrodynamics

Heimir Hjartarson1, Halldór Pálsson

1 and Magnús Þ. Jónsson

1

1Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, University of Iceland,

Hjarðarhaga 2-6, 107 Reykjavik, Iceland)

Email : [email protected]

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 [1]. 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 two-

phase 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

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

[1] C. Ballzus , Th. Karlsson and R. Maack, Design of Geothermal Steam Supply Systems in

Iceland. Geothermics 21(5/6), 835-845 (1992)

[2] G. R. Liu and M. B. Liu, Smoothed Particle Hydrodynamics: a meshfree particle method.

World Scientific publishing (2003)

[3] M. Liu and G. Liu, Smoothed Particle Hydrodynamics (SPH): an Overview and Recent

Developments. Archives of Computational Methods in Engineering 17, 25-76 (2010)

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

[email protected]

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.

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.

Thermal modelling and evaluation of boreholes for ground-source heat

pump system applications

Saqib Javed

Building services engineering, Chalmers University of Technology, Sweden.

[email protected]

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.

3D structural geological modeling and stress field analysis as core diciplines

in exploration geology for high and low enthalpy geothermal systems

Egbert Jolie1, Nicole Schulz1, Inga Moeck1

1 GFZ, Telegrafenberg, 14473 Potsdam (Section 4.1 Reservoir Technologies, GFZ German Research Centre For

Geosciences, Germany)

[email protected]

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).

Sulphur and metal transport in active geothermal systems, Iceland

Hanna Kaasalainen1,2

and Andri Stefánsson2

1Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Iceland,

2 Institute of Earth Sciences, University of Iceland, Iceland

[email protected]

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, acid-

sulphate 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

(SO32-

, SO32-

, SxO62-

). 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 9.10. 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 SiO2 together with SO4, CO2, H2S, 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

steam rich in volatiles like H2S and CO2 that may segregate from the boiled waters, rise

through and condense in shallow oxidized cold ground- and/or surface waters forming steam-

heated surface waters. In addition to major gases, the steam may also carry trace volatiles

such as B and As. In oxidized conditions, H2S tends to oxidize to sulphuric acid that

effectively leaches the surrounding rock, enhancing metal mobility. Thus, steam-heated acid-

sulphate are characterized by pH<4, with SO4, SiO2 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 CO2 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 steam-

heated 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 acid-

sulphate 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.

Primary Energy Efficiency (PEE) and CO2 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

[email protected]

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 CO2 emissions resulting from the buildings energy usage [1].

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 (fp) and

CO2 emission factor (K). These factors describe the greenhouse gas emissions in CO2

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 [1]. The factors are also discussed in EN15603, where calculation

methods and energy performance indicators for various energy sources are published [2].

Primary energy consumption and CO2 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 CO2 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

accumulated primary energy consumption and CO2 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

[3] 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 [4]. 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 CO2 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 CO2 emission factors for geothermal based heat and power production as defined in [1]

and [2]. 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

[1] 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 .

[2] EN 15603:2008. Energy performance of buildings. Overall energy use and definition of energy ratings.

Geneva: International Organisation for Standardisation (ISO).

[3] R. Bertani, Geothermal Power Generation in the World 2005 – 2010 Update Report. Proceedings World

Geothermal Congress 2010, (April 2010)

[4] J. W. Lund, D. H. Freeston, T. L. Boyd, Direct Utilization of Geothermal Energy 2010 Worldwide Review.

Proceedings World Geothermal Congress 2010, (April 2010)

Optimized geothermal binary power cycles using R134a and R410A

Evgenia Kontoleontos

1, Dimitrios Mendrinos

2, Constantine Karytsas

3

1Parallel CFD and Optimization Unit, Laboratory of Thermal Turbomachines, School of Mechanical

Engineering, National Technical University of Athens, Greece, [email protected], 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.

Fig. 1: Rankine cycle optimization - optimal solutions for R134a and R410A - the net overall

efficiency in relation to the exchangers’ surface

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

0.04

0.042

0.044

0.046

0.048

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0.06

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t o

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R134aR410A

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0.044

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plate condensershell and tube condenser

Hydrodynamic and heat transport modelling in a Hungarian fractured

basements rocks for ranking EGS sites

Éva Kun1, Tivadar M. Tóth

1, Tamás Földes

2, János Viszkok

3,

1Szeged University, Hungary, ,

2 Geotomo Kft.,

3 Central Geo Kft

[email protected], [email protected], [email protected], [email protected]

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.

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;

Tis

za

Dan

ub

e

BÜKK

VIENNA

BASIN

TRANSYLVANIANBASIN

WESTERN CARPATHIANS

HUNGARY

MECSEK

SOUTHERN CARPATHIANS

Lake Balaton

EASTERNCARPA

TH

IAN

S

Papuk

Dinarides

Eastern A

lps

Bohemian Massif200 km

PANNONIAN BASIN

APUSENI

- 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.

Thermal response test with and without artificial convection

Heiko T. Liebel1, 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

[email protected]

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

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

51-170 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: 2239-2254

Gustafsson AM, Westerlund L (2010) Multi-injection rate thermal response test in groundwater filled borehole heat exchanger. Renew Energy 35: 1061-1070

Gustafsson AM, Westerlund L, Hellström G (2010) CFD-modelling of natural convection in a groundwater-filled borehole heat

exchanger. Appl Therm Eng 30: 683-691

Mechanical deformation coupled with chemical reactions

Magnus Løberg1 and Yuri Podladchikov2

1Department of Geoscience, University of Bergen, Norway

2Institut 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.

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 0.02. 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.

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

[email protected]

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.

Dissolution of basaltic glass in seawater at 1000C and 70 bars CO2 pressure

Implications for CO2 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 CO2 in mafic rocks offers a long-term trapping of CO2. It requires the

combination of divalent metals with dissolved CO2 to form carbonate minerals. This method of in-situ

CO2 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 CO2 injection, such as separate supercritical

CO2 phase or CO2 fully dissolved in water. Both end-members have drawbacks. Supercritical CO2 is

less dense than its surrounding fluids and rocks, which will pose problems in fractured basaltic rocks.

To fully dissolve 1 ton of CO2 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 CO2 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 CO2 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 CO2 using a CO2 cylinder source up to ~45 bars. The vessel was then heated causing

the internal pressure to increase to 70 bars, driving the CO2 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 CO2 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.

Thermal Response Testing and Evaluation

Helena Nakos Building Services Engineering, Chalmers University of Technology, Sweden

[email protected]

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.

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, 14473 Potsdam, Germany.

email : [email protected]

*) 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 40 –

62 0

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 440

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, 47.3 0C) 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 (48.8 0C) which is located at about 200 m of its west.

Indonesian Site-Specific Design Optimization of Subcritical Organic-

Rankine-Cycle Geothermal Power Plant

Yodha Y. Nusiaputra1

1Institute for Nuclear and Power Engineering, Karlsruhe Institute of Technology (KIT), Germany

[email protected]

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

2010.

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.

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.

COMBINING ADAPTATION AND MITIGATION ASPECTS OF CLIMATE

CHANGE IN GEOTHERMAL DEVELOPMENT

Pacifica F. Achieng Ogola1 and Professor Brynhildur Davidsdottir2 and Dr. Ingvar Birgir Friðleifsson3

PhD Student at the University of Iceland, UNU-GTP Iceland and Kenya Electricity Generating Co. Ltd1

Director of UMAUD Environment and Natural Resources Studies at the University of Iceland2

Founding director United Nations University Geothermal Training Program, UNU-GTP Iceland3

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.

Abstract – Auður Agla Óladóttir

The object of this study is to quantify changes in soil heat and CO2 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 2006. The study is based on yearly

measurements of soil heat gradient and soil CO2 flux since 2004. The CO2 emission was

measured applying accumulation chamber methodology, which allows quick direct

measurements of the CO2 flux from soil without drastically altering the natural flux in a wide

range of fluxes. Both soil temperature and CO2 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 CO2 flux for the area. Probabilistic summary of these simulations were used to

map the flux and to calculate the total CO2 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.

Influence of weather on hydrogen sulfide distribution in Reykjavik City

Snjólaug Ólafsdóttir1, 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

[email protected]

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 (CO2) emissions. Sulfur is emitted from geothermal areas as

hydrogen sulfide (H2S), and when the areas are developed the emission is increased. H2S is a

volatile compound that may be oxidized in the atmosphere. Several environmental factors

can influence the H2S 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

2008. The Department of Environment of Reykjavik City started measuring hydrogen sulfide

(H2S) concentration at Grensasvegur Street in February 2006. In August 2007 H2S

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 H2S concentration shows

that the highest concentrations are between 85 and 110° wind. This indicates that topography

influences the movement of the H2S 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.

Toxic metal mobility following the injection of CO2 into basaltic aquifers.

J. Olsson1,2*

, S. L. S. Stipp2 and S.R.Gislason

1

1Nordic Volcanological Institute, Institute of Earth Sciences, University of Iceland, Sturlugata 7, 101 Reykjavik,

Iceland. 2Nano-Science Center, Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100

København Ø, Denmark.

Corresponding author: [email protected]

Educational level: Msc.

Injection of CO2 into rocks creates corrosive CO2 charged waters with the pH of 4 to 3 [1].

The low pH can lead to mobility of toxic metals at the early stage of water/rock interaction

[2]. 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 CO2 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 CO2 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, SO4, Ba

and CO2, 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

CO2 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 [3].

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-CO2 interaction at low pH [2,4].

References

[1] S. R. Gislason, et al., International Journal of Greenhouse Gas Control 4, pp. 537 (2010)

[2] T. H. Flaathen, et al., Applied Geochemistry 24, pp. 463 (2009)

[3] Ø. Hammer, et al., Geofluids 5, pp. 140 (2005)

[4] B. Sigfusson, et al., Environmental Science and Technology 42, pp. 8816 (2008)

Transport and precipitation of carbon and sulphur in the Reykjanes

geothermal system, Iceland

Kevin Padilla

1, Andri Stefánsson

1, Thrainn Fridriksson

2

1Department of Earth Sciences, University of Iceland, Sturlugata 7, 101 Reykjavík, Iceland

2ÍSOR, Iceland GeoSurvey, Grensásvegur 9, 108 Reykjavík, Iceland

[email protected]

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, CO2 partial

pressures of 1.45-3.86 bar and H2S partial pressures of 0.02-0.06 bar. Aquifer CO2 and H2S

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 CO2 and H2S 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 CO32-

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 ~500-1000 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

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.

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.

0.0001 0.001 0.01 0.1 1 10

Total carbon wt%

-3000

-2500

-2000

-1500

-1000

-500

0

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)

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RN17

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0.001 0.01 0.1 1 10

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The Euganean geothermal field (NE Italy): a new hydrothermal structural

model

Marco Pola1, Paolo Fabbri

1, Dario Zampieri

1

1Dipartimento di Geoscienze, Università degli Studi di Padova, Padova - Italy

Email contact: [email protected]

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 Km2 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 Mm3/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 SO4, Ca, Mg, HCO3, SiO2. 3H and

14C

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

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 three-

dimensional, two-phase, hydrothermal, ground-water flow systems.

REFERENCES

Fabbri P. (1997) Transmissivity in the Euganean Getohermal Basin: a geostatistical analysis.

Groundwater, 35(5), 881-887.

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

Distributed temperature sensing behind casing – Results from a flow test in

a hot geothermal well

Thomas Reinsch1, Jan Henninges

1, Ragnar Ásmundsson

2

1Helmholtz Centre Potsdam, German Research Centre for Geosciences GFZ, International Centre for

Geothermal Research, Potsdam, Germany 2ÍSOR - Iceland GeoSurvey, Reykjavík, Iceland

[email protected]

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 2009.

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. 0.05 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

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.

Influence of fault zones on fracture systems in sedimentary geothermal

reservoir rocks in the North German Basin

Dorothea Reyer, Sonja L. Philipp 1Adress of 1st author (Geoscience Centre, Department of Structural Geology and Geodynamics, Georg-August

Universität Göttingen, Germany)

[email protected]

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

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.

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 fault-

associated 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.

a) b)

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, e-mail contact: [email protected]

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, H2S and CO2 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 CO2, H2S, F, Cl, Na, K, Ca, Mg, B, SO4, 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,

SO4, and CO2 concentrations in the water decreased, H2S 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 SiO2, Na-

smectite, 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.

mailto:[email protected]

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 30-60 days of reaction, whereas higher

temperatures were initially obtained.

Fig. 1. Reaction path modelling of 106 g of A75 glass in 1 kg of water.

0.01 0.1 1

Reaction progress (mole rock/kg water))

1E-007

1E-006

1E-005

0.0001

0.001

0.01

0.1

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Quartz

Calcite

Clinochlore 14-A

pH

Pyrite

Anatase

Chamosite 7-A

Montmorillonite Na

Flourite

Illite

4.0

5.0

6.0

7.0

8.0

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Quartz

Montorillonite Na

Clin

och

lore

14-ApH

Anatase

106 g of Askja 1875 glass in 1 kg of water(1000 steps)

Analcime

Cham

osite 7

-A

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te

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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

Email contact of the summer school participant for future correspondance

[email protected]

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.

Density and Viscosity Effect on Heat Transfer in Porous Media:

Sanaz Saeid - CITG [email protected]

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%.

Tectonic and structural control on geothermal fields of the Biga Peninsula,

Northeastern Aegean

Matias Sanchez Schneider (MSc. PhD student); [email protected]

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.

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

Gas Chemistry of the Hellisheiði Geothermal Field

Samuel Scott1, Ingvi Gunnarsson3, Andri Stefánsson

2, Stefán Arnórsson

2, Einar

Gunnlaugsson3 1 Reykjavík Energy Graduate School of Sustainable Systems, Baejarhalsi 1, 110 Reykjavík, Iceland

2University of Iceland, Institute of Earth Science, Sturlugata 7, 101 Reykjavík, Iceland

3Reykjavík Energy, Baejarhalsi 1, 110 Reykjavík, Iceland

[email protected]

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 (CO2, H2S, H2 and

CH4). 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 H2S and H2

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.

Petrophysical characteristics of sandstones dating from the Buntsandstein

in the Upper Rhine Graben: case of the borehole EPS1 (Soultz-Sous-Forêts,

France)

HAFFEN Sébastien1, GERAUD Yves

1, DIRAISON Marc

1, DEZAYES Chrystel

2

11, rue Blessig 67084 Strasbourg (EOST – Université de Strasbourg, France)

2BRGM Dpt Geothermal Energy – Orleans, France

[email protected]

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 playa-

lake 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.

Quantification of geochemical energy in geothermal ecosystems

Ásgerður K. Sigurðardóttir1, Andri Stefánsson

1, Guðmundur Óli Hreggviðsson

2, Snædís

Björnsdóttir2 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

[email protected]

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 (NH4, NO2, NO3), S (H2S, S2O3, SO4), H2O (O2,

H2, H+), and C (CH4, CO2) using combination of titrations, ion chromatography and

colorimetric techniques. The pH of the water and the temperature range were 3-9 and 50–90

°C, respectively. Combined with thermodynamic calculations of the appropriate redox

reactions, the non-equilibrium excess energies (chemical affinities, Ar) 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 S2O32-

by

O2 and H2, respecitively. Other reactions of importance involved oxidation or reduction of

S(s) and SO42-

, H2S and SO42-

and S2O32-

and SO42-

. The overall trend was found to be

relatively insensitive to pH and temperature and whether the reaction was written as oxidation

H+ to H

2(aq) and ...

pH

3 4 5 6 7 8 9

Ch

em

ical

aff

init

y (

kcal/

mo

l e

- )

-40

-30

-20

-10

0

10

20

H2S to S(s)

H2S to S2O3

H2S to SO4

S(s) to S2O3

S(s) to SO4

S2O3 to SO4

H2S to pyrite

pyrite to S(s)

pyrite to S2O3

pyrite to SO4

O2(aq) to H

2O and ...

pH

3 4 5 6 7 8 9

Ch

em

ica

l a

ffin

ity (

kc

al/

mo

l e

- )

-40

-30

-20

-10

0

10

20

H2S to S(s)

H2S to S2O3

H2S to SO4

S(s) to S2O3

S(s) to SO4

S2O3 to SO4

H2S to pyrite

pyrite to S(s)

pyrite to S2O3

pyrite to SO4

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.

Fig. 1. The calculated chemical affinity (Ar) 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.

Thermal and Structural Analysis of the Production

Casing in a High Temperature Geothermal Well

Gunnar Skúlason Kaldal1*, Magnús Þ. Jónsson

1, Halldór Pálsson

1, Sigrún N. Karlsdóttir

2,

Ingólfur Ö. Þorbjörnsson2,3

1Faculty 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 3Reykjavik University, Menntavegur 1, Reykjavik, 101, Iceland

*e-mail: [email protected]

MSc (PhD student)

The production casing of a high temperature geothermal well is subjected to multiple thermo-

mechanical 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.

Evaluation of suitable working fluids for single ORC by the concept of

power maximization C. Steins1, M. Habermehl1 & R. Kneer1 1Institute of Heat and Mass Transfer, RWTH Aachen University, Eilfschornsteinstraße 18, 52064 Aachen,

Germany

[email protected]

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).

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 maximisation1.

1 A. Bejan. Entropy Generation Minimization – The Method of Thermodynamic Optimization of Finite-Size

Systems and Finite-Time Processes. CRC Press, 1996.

Thermal configuration and homeothermal surface of shallow aquifer in

Piemonte plain (NW Italy) Marco STRINGARI

1 [email protected] – Riccardo BALSOTTI

2 – Domenico Antonio

DE LUCA3

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

Email: [email protected]; [email protected] 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.



Supercritical Organic Rankine Cycle for optimized power

generation from geothermal heat

Christian Vetter

Institute for Nuclear and Energy Technologies

Karlsruhe Institute of Technology (KIT)

Hermann-von-Helmholtz-Platz 1

76344 Eggenstein-Leopoldshafen

Germany

[email protected]

Educational level: Ph.D.-Student

Electricity generation from geothermal heat is still in its infancy in Germany. Due to the

thermal water temperature of typically 100 °C to 170 °C only very low net efficiencies of

typically 8 % at the common methods such as ORC (Organic Rankine Cycle) - or Kalina

processes are feasible.

The work at the Institute for Nuclear and Energy Technologies follows the approach to

maximize power generation from geothermal energy by choosing a suitable working fluid in

the power circuit and by the implementation of proven strategies of power plant technology

optimization.

The performance of the ORC process at a given geothermal water temperature depends on

various parameters. To analyse processes with varying parameters (e.g. steam pressure and

temperature, condensation temperature) a simulation program in Microsoft Visual Basic for

Applications (VBA) has been developed and integrated into Microsoft Excel. It enables the

optimization of ORC processes with various substances as working fluids. The

thermodynamic fluid data were imported via an add-in from the database REFPROP of the

National Institute of Standards and Technology (NIST).

Up to today subcritical ORC-processes with refrigerants such as isopentane or isobutane are

state of the art. An innovative approach is the use of working fluids which can be used under

supercritical conditions. First calculations with propane and a thermal water temperature of

150 °C have shown that improvements of net power output up to 30 % can be achieved. Further

investigations showed that the choice of a suitable working fluid, depending on the given

thermal water temperature, has substantial influence on the maximum achievable net output.

The crucial factor is not only the thermal efficiency of the process. Also significant impact

has the temperature of the thermal water after the heat exchanger and associated to that the

heat supplied to the process. Supercritical processes of suitable fluids offer a better adaption

of the temperature curves of the thermal water and the working fluid in a counter current heat

exchanger, which enables to cool down the thermal water to lower temperatures.

In the scope of my dissertation, a low-enthalpy cycle process for power generation has to be

developed and optimized in terms of net power output. The innovative approach by using a

supercritical working fluid leads to necessary adjustments of system components to the

properties of the fluid due to the operation in the supercritical state. The highly variable fluid

properties near the critical point and the different physical models for the description of the

processes require a systematic and basic approach for the design and optimization of the

components. This should be taken into account by analytical approaches, and inter alia by

means of CFD simulations.

Shown in Figure 1a is a simplified scheme of the investigated system, consisting of feed

pump, heat exchanger, turbine and condenser. Figure 1b shows the temperature-entropy-

diagram of the supercritical ORC-process with propane. More detailed simulations (e.g. part

load behaviour) will be done in future investigations.

Figure 1a: Simulated system

Figure 2b: T-s-diagramm of a supercritical

ORC-process with propane

Application of Geo-Parameters for Borehole Stability Modeling from

LWD-Measurements in the North German Basin Esther Vogt and Thomas Wonik Leibniz Institute for Applied Geophysics, Hannover - Germany

[email protected]

Dipl.-Geophys.

This presentation is based on the German gebo-project (Geothermal Energy and High

Performance Drilling), which intends to make drilling for deep geothermal energy in

Northern Germany safer and more efficient. To do so is necessary to know more about

borehole stability during the drilling process which is controlled mainly by the density

of the drilling mud. Choosing the right mud weight prevents the borehole from

collapsing and averts accidental fracturing of the formation. Computation of the feasible

window of mud weight requires input of several crucial parameters like pore pressure,

osmotic pressure, and fracture gradient. Some of these can be directly measured while

drilling, at least in permeable formations. Others can be modeled or calculated from

different measurable quantities and while some can only be estimated from published

values based on the lithology.

This research aims to find correlations and evaluating models to calibrate the input

parameters applicable for the North German Basin. Up to now the main focus has been

on pore pressure and osmotic pressure considerations.

Pore pressure is one of the most important parameters for borehole stability and can

only be measured while drilling in permeable formations. The commonly used empiric

models were developed for young sedimentary basins where many wells for oil and gas

production are located. Under compaction is the main reason for high pressure in such

basins. Consequently, the high sedimentation rates prevent the water from discharging

causing over pressure when the sediment is buried. We applied two standard models on

a location in the much older North German Basin. Neither of these fit for these

conditions. A possible reason is that the over pressure caused by under compaction

adjusted over time, therefore, other mechanisms causing overpressure have to be

considered, such as rising temperature, chemical transformations, and tectonic

influence.

Osmotic pressure builds up in clay layers which work as semipermeable membrane

between formation water and drilling mud. Differences in concentration of solved

substances leads to a flow of water from the lower concentrated fluid to the higher

concentrated fluid. Since flow of water from the formation into the borehole and vice

versa is not desirable, it is of interest to know the concentrations in pore fluid and mud.

The composition of mud is easily measured, but the concentration of ions in the pore

fluid can only be calculated by measuring the resistivity while drilling. It depends on

type and concentration of dissolved ions and the temperature of the fluid. While

temperature and resistivity are quantifiable composition of ions needs to be estimated.

Therefore, we applied the inverse or backward modeling by taking analyses of pore

fluids from neighboring wells which were used to pick the main components for the

relevant formations, calculate the resistivity, and compare it with the measured

temperature and resistivity. For low temperatures conductivities are calculated with

PHREEQC. For higher temperatures, up to 200°C, charts based on empiric data are

applied since PHREEQC does not work for such conditions.

Conductivities calculated with

PHREEQC and taken from the

Schlumberger‐ chart Gen‐ 9.

The TDS (total dissolved

solids) content is based on

analyses in the North German

Basin as well as the

temperature which increases

from point to point by 17,5°C.

The next step is to verify the calculation method for osmotic pressure with some

measured data. If it turns out to fulfill the expectations, a dataset with pore fluid

compositions needs to be created. Furthermore, the pore pressure results can be

compared with measured data and local geology to determine the causes of over

pressure and develop a working model.

Conceptual Model for Coupling Power Plant with Deep Reservoirs

Names of author – LiWah, WONG

Helmholtz Centre Potsdam

GFZ German Research Centre for Geosciences

Section 4.1: Reservoir Technologies

Telegrafenberg

D-14473 Potsdam

Germany

[email protected]

MSc. (Georg August Universität Göttingen, 2008-2010)

PhD (GFZ German Research Centre for Geosciences)

Hydro-mechanical-thermal variation is important in a process of geothermal power

production which consists of four major aspects viz reservoirs, boreholes, heat exchangers

and power plants. Existing simulations are all partial therein lies the simplication of

interactions between all aspects and lack of interfaces between all partial simulations.

Multiphysics is introduced as an approach of iteration to couple all aspects , including coupled

processes particularly fluid flow and heat transfer, thereafter allows arbitrary couplings to

other physics interfaces says chemical couplings.

It is initialized by a subsurface geothermal water cycle coupling, which brings together the

reservoir and boreholes, followed by a connection to the surface heat exchanger cycle, which

brings the injection well and the production well into the former couple

, and finally an overall coupled simulation which includes the power plant cycle coupling.

Sensitivity analysis will be performed with respect to field data from Groß Schönebeck,

Germany, with a lifespan of 30 years taken into account.

This coupling is essential to predict the life cycle behaviour of reservoir thereafter the

cumulated electricity provision of the overall geothermal system.

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