Geothermal Energy Systems E-Book

• Herausgeber: Wiley-VCH
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 797

Veröffentlichungsjahr: 2011

Beschreibung

Presenting boundary conditions for the economic and environmental utilization of geothermal technology, this is the first book to provide basic knowledge on the topic in such detail. The editor is the coordinator of the European Geothermic Research Initiative, while the authors are experts for the various geological situations in Europe with high temperature reservoirs in shallow and deep horizons. With its perspectives for R&D in geothermic technology concluding each chapter, this ready reference will be of great value to scientists and decision-makers in research and politics, as well as those giving courses in petroleum engineering, for example.

Leseprobe

Contents

Preface

List of Contributors

1 Reservoir Definition

1.1 Expressions of Earth’s Heat Sources

1.2 Heat Flow and Deep Temperatures in Europe

1.3 Conceptual Models of Geothermal Reservoirs

2 Exploration Methods

2.1 Introduction

2.2 Geological Characterization

2.3 Relevance of the Stress Field for EGS

2.4 Geophysics

2.4.2.3 Passive Seismic Methods

2.5 Geochemistry

3 Drilling into Geothermal Reservoirs

3.1 Introduction

3.2 Drilling Equipment and Techniques

3.3 Drilling Mud

3.4 Casing and Cementation

3.5 Planning a Well

3.6 Drilling a Well

3.7 Well Completion Techniques

3.8 Risks

3.9 Case Study Groß Schönebeck Well

3.10 Economics (Drilling Concepts)

4 Enhancing Geothermal Reservoirs

4.1 Introduction

4.2 Initial Situation at the Specific Location

4.2.2 Appropriate Stimulation Method According to Geological System and Objective

4.3 Stimulation and Well path Design

4.4 Investigations Ahead of Stimulation

4.5 Definition and Description of Methods (Theoretical)

4.6 Application (Practical)

4.7 Verification of Treatment Success

4.8 Outcome

4.9 Sustainability of Treatment

4.10 Case Studies

5 Geothermal Reservoir Simulation

5.1 Introduction

5.2 Theory

5.3 Reservoir Characterization

5.4 Site Studies

5.5 Groß Schönebeck

5.6 Bad Urach

5.7 Rosemanowes (United Kingdom)

5.8 Soultz-sous-Forets (France)

5.9 KTB (Germany)

5.10 Stralsund (Germany)

6 Energetic Use of EGS Reservoirs

6.1 Utilization Options

6.2 EGS Plant Design

6.3 Case Studies

7 Economic Performance and Environmental Assessment

7.1 Introduction

7.2 Economic Aspects for Implementing EGS Projects

7.3 Impacts on the Environment

8 Deployment of Enhanced Geothermal Systems Plants and CO2 Mitigation

8.1 Introduction

8.2 CO2 Emission by Electricity Generation from Different Energy Sources

8.3 Costs of Mitigation of CO2 Emissions

8.4 Potential Deployment

8.5 Controlling Factors of Geothermal Deployment

Color Plates

Index

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The EditorDr. Ernst HuengesGeoForschungsZentrumPotsdamTelegrafenberg14473 PotsdamGermany

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Preface

The book presents basic knowledge about geothermal technology for the utilization of geothermal resources. It helps to understand the basic geology needed for the utilization of geothermal energy and describes the methods to create access to geothermal reservoirs by drilling and the engineering of the reservoir. The book describes the technology available to make use of the earth’s heat for direct use, power, and/or chilling, and gives the economic and environmental conditions limiting its utilization. Special emphasis is given to enhanced or engineered geothermal systems (EGS), which are based on concepts that bring a priori less productive reservoirs to an economic use. These concepts require the geothermal technology described here. The idea of EGS is not yet very old. Therefore, this book aims to provide a baseline of the technologies, taking into account the fact that due to a growing interest in EGS, a dynamic development may increase the specific knowledge to a large extent in the near future.

The book begins with a large-scale picture of geothermal resources, addressing expressions of the earth’s heat sources and measured heat flow at different places world wide. This leads to conceptual models with a geological point of view influencing geothermal reservoir definitions based on physical parameters like porosity, permeability, and stress distribution in the underground, indicating that geothermal applications can be deployed anywhere, but some locations are more favorable than others.

The second chapter addresses the characterization of geothermal reservoirs and the implications of their exploration. A best practice for the exploration of EGS reservoirs is still to be determined and the different methods in geology, geophysics, and geochemistry have a strong local character. Some methods are successful in exploring conventional geothermal reservoirs like the magnetotellurics, whereas for EGS, seismic methods become more and more important. An overall conceptual exploration approach integrating the geophysical measurements into a geological model taking into account the earth’s stress conditions is addressed in this chapter, but it has to be further developed in future contributions.

The baseline know-how of EGS drilling given in the third chapter, is based on a few case studies and therefore, somewhat different from hydrocarbon drilling with reference to issues like large diameter holes, deviated wells, and mitigation of formation damage. The latter is also important for drilling conventional geothermal reservoirs, which to a great extent follow standards in operation and completion. The knowledge of underground physical conditions, especially the magnitude and direction of the local stress, is important for reliable drilling into EGS reservoirs. Awareness of the stress conditions is also a prerequisite for starting hydraulic fracturing treatment which is addressed in a following chapter.

In the fourth chapter, techniques and experiences from several EGS sites are described providing a set of methods available for addressing the goal of increasing well productivity. The case studies cover several geological environments such as deep sediments and granites. Significant progress was made in the last few years in recovering enhancing factors in the order of magnitudes. Chances and risks of companion effects of the treatments, such as induced seismicity, are addressed and will be a subject of forthcoming research.

In the fifth chapter, the state-of-the-art numerical instruments used to simulate geothermal reservoirs during exploitation are given in different case studies. Different coupled processes such as thermal–hydraulic or hydraulic–mechanical, including coupled chemical processes, are discussed. The development of the coupling of thermal, hydraulic, mechanical, and chemical processes is ongoing, hence the chapter provides the basics.

The benefits of using geothermal energy technologies for the direct use and conversion of the earth’s heat into chilling or heating power (as required), are described in the sixth chapter. Technical solutions for all tasks within the goal of energy provision exist, and approaches for improving the performance of system components are given. Special emphasis is given to techniques that can assure reliable and efficient operation at the interface of underground fluids with technical components. Processes like corrosion and scaling have to be addressed and they are still a subject of future research.

The economic learning curve is shown in the seventh chapter that provides some methods to analyze the risks of a project. A decision-making methodology is given for several stages of the project. Environmental aspects are discussed, and results of life cycle assessment with illustrations of greenhouse gas emissions are reported in the chapter.

The final chapter discusses the possibility of geothermal deployment as a part of future energy provision and an important contribution to the mitigation of CO2 emissions. The technological, economic, and political factors controlling such deployment are discussed and should provide some assistance for decision makers.

The book was compiled by the authors, but also significantly improved by competent reviewers. Therefore, we like to thank Magdalene Scheck-Wenderoth, Albert Genter, Dominique Bruel, Claus Chur, Don DiPippo, Wolfram Krewitt, and Harald Milsch for their excellent comments on the different chapters. In addition, we acknowledge the funds received from the EU commission, for example, for the projects ENGINE and I-GET, and the German government, especially, the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU). Special thanks go to the coworkers of the International Centre for Geothermal Research at the Helmholtz Centre in Potsdam. These colleagues assisted the development of the book with fruitful discussions over the last two years.

Ernst HuengesPotsdam, GermanyDecember 2009

List of Contributors

Mando G. BlöcherHelmholtz Centre Potsdam GFZGerman Research Centre forGeosciencesReservoir TechnologiesTelegrafenberg A6 R. 10414473 PotsdamGermany

Wulf BrandtHelmholtz Centre Potsdam GFZGerman Research Centre forGeoscienceInternational Centre forGeothermal ResearchTelegrafenberg14473 PotsdamGermany

Dominique BruelEcole des Mines de ParisCentre de Géosciences35 rue Saint-Honoré77300 FontainebleauFrance

David BruhnHelmholtz Centre Potsdam GFZGerman Research Centre forGeoscienceInternational Centre forGeothermal ResearchGermany

Christoph ClauserApplied Geophysics andGeothermal EnergyE.ON Energy Research CenterRWTH Aachen UniversityMathieustr. 6,E.ON ERC Gebäude52074 AachenGermany

Hans-Jörg G. DierschWASY Gesellschaft fürwasserwirtschaftliche Planungund Systemforschung mbHWalterdorfer Straße 10512526 Berlin-BohnsdorfGermany

Kemal ErbasHelmholtz Centre Potsdam GFZGerman Research Centre forGeoscienceInternational Centre forGeothermal ResearchTelegrafenberg14473 PotsdamGermany

James FauldsUniversity of NevadaNevada Bureau of Minesand GeologyMackay School of MinesReno, NVUS

Stephanie FrickHelmholtz Centre Potsdam GFZGerman Research Centre forGeoscienceInternational Centre forGeothermal ResearchTelegrafenberg14473 PotsdamGermany

Laurent Guillou-FrottierBureau de RecherchesGéologiques et Minières (BRGM)Mineral Resources Division3 av. C. GuilleminBP3600945060 Orléans Cx 2France

Ernst HuengesHelmholtz Centre Potsdam GFZGerman Research Centre forGeoscienceInternational Centre forGeothermal ResearchTelegrafenberg14473 PotsdamGermany

Reiner JathoFederal Institute for Geosciencesand Natural Resources (BGR)Stilleweg 230655 HannoverGermany

Ralf JunkerLeibniz Institute for AppliedGeophysicsStilleweg 230655 HannoverGermany

Martin KaltschmittTechnische UniversitätHamburg-HarburgInstitute for EnvironmentalTechnology and Energy EconomicEißendorfer Straße 4021073 HamburgGermany

Thomas KohlGeoWatt AGDohlenweg 288050 ZürichSwitzerland

Olaf KolditzHelmholtz Centre forEnvironmental ResearchDepartment of EnvironmentalInformaticsTU Dresden, EnvironmentalSystems AnalysisPermoser Str. 1504318 LeipzigGermany

Stefan KranzHelmholtz Centre Potsdam GFZGerman Research Centre forGeoscienceInternational Centre forGeothermal ResearchTelegrafenberg14473 PotsdamGermany

Michael KühnHelmholtz Centre Potsdam GFZGerman Research Centre forGeoscienceInternational Centre forGeothermal ResearchTelegrafenberg14473 PotsdamGermany

Patrick LedruAREVA Business Group MinesKATCOAv. Dostyk 282050000 ALMATYKazakhstan

Adele ManzellaNational Research CouncilInstitute of Geosciences andEarth ResourcesPisaItaly

Chris McDermottUniversity of EdinburghSchool of GeoSciencesUK

Inga MoeckHelmholtz Centre Potsdam GFZGerman Research Centre forGeoscienceInternational Centre forGeothermal ResearchTelegrafenberg14473 PotsdamGermany

Sandrine PortierCentre de recherche engéothermie (CREGE)University of NeuchâtelEmile-Argand 11, CP 1582009 NeuchâtelSwitzerland

Simona RegenspurgHelmholtz Centre Potsdam GFZGerman Research Centre forGeoscienceInternational Centre forGeothermal ResearchTelegrafenberg14473 PotsdamGermany

Ali SaadatHelmholtz Centre Potsdam GFZGerman Research Centre forGeoscienceInternational Centre forGeothermal ResearchTelegrafenberg14473 PotsdamGermany

Gerd SchröderLeipziger Institut für EnergieGmbHTorgauer Strape 11604347 LeipzigGermany

Thomas SchulteHelmholtz Centre Potsdam GFZGerman Research Centre forGeoscienceInternational Centre forGeothermal ResearchTelegrafenberg14473 PotsdamGermany

Axel SperberIng. Büro A. SperberEddesser Straße 131234 EdemissenGermany

Torsten TischnerFederal Institute for Geosciencesand Natural Resources (BGR)Stilleweg 230655 HannoverGermany

Jan Diederik Van WeesVrije Universiteit AmsterdamIntegrated Basin InformationSystemsDe Boclean 10851081 HV AmsterdamThe Netherlands

Francois VuatazCentre de recherche engéothermie (CREGE)University of NeuchâtelEmile-Argand 11, CP 1582009 NeuchâtelSwitzerland

Wenqing WangHelmholtz Centre forEnvironmental Research–UFZEnvironmental System AnalysisGermany

Norihiro WatanabeHelmholtz Centre forEnvironmental Research–UFZEnvironmental System AnalysisGermany

Günter ZimmermannHelmholtz Centre Potsdam GFZGerman Research Centre forGeosciences International Centrefor Geothermal ResearchTelegrafenberg14473 PotsdamGermany

1

Reservoir Definition

Patrick Ledru and Laurent Guillou Frottier

1.1 Expressions of Earth’s Heat Sources

1.1.1 Introduction to Earth’s Heat and Geothermics

Scientific background concerning the heat flow and the geothermal activity of the earth is of fundamental interest. It is established that plate tectonics and activities along plate margins are controlled by thermal processes responsible for density contrasts and changes in rheology. Thus, any attempt to better understand the earth’s thermal budget contributes to the knowledge of the global dynamics of the planet. Information on the sources and expressions of heat on earth since its formation can be deduced from combined analyses of seismic studies with mineral physics, chemical composition of primitive materials (chondrites), as well as pressure–temperature–time paths reconstituted frommineralogical assemblages in past and eroded orogens.

Knowledge of heat transfer processes within the earth has greatly improved our understanding of global geodynamics. Variations of surface heat flow above the ocean floor has provided additional evidence for seafloor spreading (Parsons and McKenzie, 1978), and improved theoretical models of heat conduction within oceanic plates or continental crust helped to constrain mantle dynamics (Sclater, Jaupart, and Galson, 1980; Jaupart and Parsons, 1985). When deeper heat transfer processes are considered, thermal convection models explain a number of geophysical and geochemical observations (Schubert, Turcotte, and Olson, 2002). It must be, however, noted that at a smaller scale (closer to the objective of this chapter), say within the few kilometers of the subsurface where water ismuchmore present than at depths, a number of geological and geothermal observations are not well understood. As emphasized by Elder (1981), crustal geothermal systems may appear as liquid- or vapor-dominated systems, where physics of water–rock interactions greatly differs from one case to the other. Actually, as soon as hydrothermal convection arises among the active heat transfer processes, everything goes faster since heat exchanges are more efficient than without circulating water. It is thus important to delineate which type of heat transfer process is dominant when geothermal applications are considered. Examples of diverse geothermal systems are given below.

Within the continental crust, a given heat source can be maintained for distinct time periods according to the associated geological system. Hydrothermal fields seem to be active within a temporal window around 104–105 years (Cathles, 1977), whereas a magma reservoir would stay at high temperatures 10–100 times longer (Burov, Jaupart, and Guillou-Frottier, 2003). When radiogenic heat production is considered, half-lives of significant radioactive elements imply timescales up to 109 years (Turcotte and Schubert, 2002). At the lower limit, one can also invoke phase changes of specific minerals involving highly exothermic chemical reactions (e.g., sulfide oxidation and serpentinization) producing localized but significant heat excess over a short (103–104 years) period (Emmanuel and Berkowicz, 2006; Delescluse and Chamot-Rooke, 2008). Thus, description and understanding of all diverse expressions of earth’s heat sources involve a large range of physical, chemical, and geological processes that enable the creation of geothermal reservoirs of distinct timescales.

Similarly, one can assign to earth’ heat sources either a steady state or a transient nature. High heat producing (HHP) granites (e.g., in Australia, McLaren et al., 2002) can be considered as permanent crustal heat sources, inducing heating of the surrounding rocks over a long time. Consequently, thermal regime around HHP granites exhibits higher temperatures than elsewhere, yielding promising areas for geothermal reservoirs. On the contrary, sedimentary basins where heat is extracted from thin aquifers may be considered as transient geothermal systems since cold water reinjection tends to decrease the exploitable heat potential within a few decades.

Finally, regardless of the studied geological system, and independent of the involved heat transfer mechanism, existence of geothermal systems is first conditioned by thermal regime of the surroundings, and thus by thermal boundary conditions affecting the bulk crust. Consequently, it is worth to understand and assess the whole range of thermal constraints on crustal rocks (physical properties as well as boundary conditions) in order to figure out how different heat transfer mechanisms could lead to generation of geothermal systems.

The following subsections present some generalities on earth’ heat sources and losses in order to constrain thermal boundary conditions and thermal processes that prevail within the crust. Once crustal geotherms are physically constrained by the latter and by rock thermal properties, distinct causes for the genesis of thermal anomalies are discussed.

1.1.2 Cooling of the Core, Radiogenic Heat Production, and Mantle Cooling

The earth’s core releases heat at the base of the mantle, through distinct mechanisms. Inner-core crystallization, secular cooling of the core, chemical separation of the inner core, and possibly radiogenic heat generation within the core yield estimates of core heat loss ranging from 4 to 12 TW (Jaupart, Labrosse, and Mareschal, 2007). Precise determinations of ohmic dissipation and radiogenic heat production should improve this estimate. Independent studies based on core–mantle interactions tend to favor large values (Labrosse, 2002), while according to Roberts, Jones, and Calderwood (2003), ohmic dissipation in the earth’s core would involve between 5 and 10TW of heat loss across the core–mantle boundary. The averaged value of 8 TW (Jaupart, Labrosse, and Mareschal, 2007) is proposed in Figure 1.1.

Figure 1.1 Heat sources and losses in the earth’s core and mantle. (After Jaupart, Labrosse, and Mareschal, 2007.)

The earth’s mantle releases heat at the base of the crust. Radiogenic heat production can be estimated through chemical analyses of either meteorites, considered as the starting material, or samples of present-day mantle rocks. Different methods have been used; the objective being to determine uranium, thorium, and potassium concentrations. Applying radioactive decay constants for these elements, the total rate of heat production for the bulk silicate earth (thus including the continental crust) equals 20 TW, among which 7TW comes from the continental crust. Thus, heat production within the mantle amounts to 13TW (, Jaupart, Labrosse, and Mareschal, 2007). Since total heat loss from the mantle is larger than heat input from the core and heat generation within it, the remaining heat content stands for mantle cooling through earth’s history.