University of Groningen the Conductive Geothermal Field
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University of Groningen The conductive geothermal field as an energy and economic entity Daniilidis, Alexandros IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2017 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Daniilidis, A. (2017). The conductive geothermal field as an energy and economic entity: Effects and implications for the province of Groningen, North-East Netherlands. [Groningen]: University of Groningen. Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). 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Download date: 12-11-2019 The conductive geothermal field as an energy and economic entity Effects and implications for the province of Groningen, North-East Netherlands 514166-L-bw-Daniilidis Processed on: 11-10-2017 PDF page: 1 Alexandros Daniilidis The conductive geothermal field as an energy and economic entity Effects and implications for the province of Groningen, North-East Netherlands This work formed part of the Flexiheat project and was supported by Samenwerkingsverband Noord Nederland (SNN) and the Dutch Ministry of Economic Affairs The research reported in this thesis was carried out at the Geo-energy group, which is part of the Energy and Sustainability Research Institute Groningen (ESRIG) of the University of Groningen, according to the requirements of the graduate school of the faculty of Science and Engineering, University of Groningen The printing of this thesis was partially supported by the graduate school of the faculty of Science and Engineering. ISBN: 978-94-028-0796-7 Copyright © 2017, Alexandros Daniilidis Cover design and layout: Alexandros Daniilidis The cover data represent the modelled hourly heat demand data in the Groningen geothermal system. 514166-L-bw-Daniilidis Processed on: 11-10-2017 PDF page: 2 The conductive geothermal field as an energy and economic entity Effects and implications for the province of Groningen, North-East Netherlands PhD thesis to obtain the degree of PhD at the University of Groningen on the authority of the Rector Magnificus Prof. E. Sterken and in accordance with the decision by the College of Deans. This thesis will be defended in public on Friday October 27th at 16.15 hours by Alexandros Daniilidis born on September 26th 1983 in Stockholm, Sweden 514166-L-bw-Daniilidis Processed on: 11-10-2017 PDF page: 3 Supervisor Prof. M.A. Herber Assessment Committee Prof. H.A.J. Meijer Prof. D.M.J. Smeulders Prof. D. Bruhn 514166-L-bw-Daniilidis Processed on: 11-10-2017 PDF page: 4 “The antique people are down in the dungeons Run by machines and afraid of the tax Their heads in the grave and their hands on their eyes Hauling their hearts around circular tracks Pretending forever their masquerade towers Are not really riddled with widening cracks And I wave goodbye to iron And smile hello to the air” Tim Buckley, 1967 514166-L-bw-Daniilidis Processed on: 11-10-2017 PDF page: 5 6 | 514166-L-bw-Daniilidis Processed on: 11-10-2017 PDF page: 6 CONTENTS Summary 9 Samenvatting 13 Introduction & Thesis Outline 17 Higher energy recovery at shallower depths 39 Assessing the Groningen geothermal potential and uncertainty 61 Geochemical implications of coupling a direct use geothermal system with surface demand 91 Techno-Economic uncertainty 119 Discussion and outlook 147 References 159 Acknowledgements 173 List of publications 179 About the author 181 | 7 514166-L-bw-Daniilidis Processed on: 11-10-2017 PDF page: 7 514166-L-bw-Daniilidis Processed on: 11-10-2017 PDF page: 8 SUMMARY Geothermal sources provide renewable energy that can be used for electricity or heat generation (Chapter 1). This thesis is aimed at identifying and analyzing potential geothermal fields in the conduction-dominated geological setting of NE Netherlands in two different ways. The first consists of exploring and harvesting the high heat flow through salt. The second is a step-wise, incremental approach in outlining, assessing, characterizing and evaluating the development of the Groningen geothermal system. The high thermal conductivity of salt in comparison with other sediments is significant for the temperature field in a conductive geological setting (Chapter 2) as it describes a locally higher geothermal gradient. The presence of this anomaly lowers the threshold for accessing the heat resource (in terms of capacity, time and, most critically for geothermal projects, cost) and enhances the renewability of the resource. In the study area, salt causes temperature anomalies proportional to its thickness. A critical minimum thickness was identified (~600m). Temperature differences up to 25°C were modelled between the top of the salt structure and the surrounding strata at the same depth. If a suitably permeable formation is overlying this sweet spot, up to 40% more energy can be extracted, while the field recovery time is only being prolonged by 13%. In the Dutch context, the provinces of Drenthe and Groningen are likely candidates for application of this principle, as local salt thickness can exceed 800m. Just as any subsurface development, geothermal projects are subject to uncertainties. In this thesis a comprehensive analysis is devoted to assess not only individual uncertainties, | 9 514166-L-bw-Daniilidis Processed on: 11-10-2017 PDF page: 9 but also their interaction. In order to cover ranges of uncertainties the approach is based on stochastics. The combined uncertainty associated with reservoir initial state (pressure and gas saturation levels), geology (reservoir and fault permeability) and operations (flow rate levels and re-injection temperature) are analyzed for the Groningen geothermal system (Chapter 3). The reservoir initial state principally affects the pressure difference between the producer well and a hydrostatic reservoir, as well as the produced gas volume. Pressure depletion dictates the required pump depth, while gas saturation potentially contributes to the project finances but also complicates the pump installation and operation. Of the geological parameters, reservoir permeability is tightly connected to the pressure difference between the wells. Fault permeability affects the drainage area and thus has a temporal effect on the produced temperature. Of the operational parameters, the chosen flow rate controls the produced thermal power, the well pressure difference and the producer temperature. The injection temperature also affects the produced thermal power over time. System complexity is increased when the geothermal resource is coupled with the demand pattern of the surface system (Chapter 4). This introduces seasonal load factors, together with uncertainty regarding the robustness of supply, as well as possible geochemical implications. For the Groningen case, it is shown that coupling the seasonal surface demand with the subsurface supply causes no adverse geochemical effects on the reservoir and energy generation during a production time of 50 years. Moreover, the seasonally variable production enables a more efficient use of the geothermal resource by delaying the propagation of the cold front. This variability is found to affect only the rate and not the nature of the changes in the chemical reservoir properties. The geochemical behavior of the reservoir is mostly affected by flow rate, and secondarily by the injection pH and injection temperature. In the Rotliegend Sandstone, anhydrite and dolomite are identified as the two key minerals. Anhydrite dissolves during the first years of production leading to increased permeability around the injector well. The flow rate control strategy influences the rate of dissolution, but the investigated flow rate control strategies all result in the dissolution of the same volume fraction. Dolomite has an effect on the permeability at a later time and its change rate is primarily affected by pH and secondarily by temperature. Acidic pH and lower temperatures favor dolomite dissolution while a neutral pH and higher temperatures favor precipitation. Bringing together technical and economic uncertainties provides a comprehensive overview of geothermal field development (Chapter 5). A probabilistic, techno- economic model incorporates uncertainty for both the geological and the economic parameters. 10 | 514166-L-bw-Daniilidis Processed on: 11-10-2017 PDF page: 10 Summary The Expected Monetary Value (EMV) shows a 50% probability for marginal profits at the end of a 40 years period, mostly affected by the success rate of drilling the wells. However, even if both wells are successfully drilled, still a net deficit remains as a possible outcome. The Net Present Value (NPV) is mostly sensitive to operational and initial state parameters, while the Levelised Cost of Heat (LCOH) is principally affected by geological and operational parameters.