GEOTHERM-2

In GEOTHERM-2 we propose to examine the linkage between b-value and the statistical characteristics of stress heterogeneity within the Soultz and Basel reservoirs (as derived from the work conducted in GEOTHERM-1. A novel aspect of this work is 'challenging' the hypothesis: significant spatial variations in b-value were found within both reservoirs (Bachmann et al., 2011), which may reflect stress variations. We propose to explore the possibility of extracting information about the length distribution of fracture populations within the reservoir from the stress orientation and magnitude variations.
The second theme which we would like to pursue concerns coupled thermo-mechanical-hydraulic process involved in thermal stimulation within the near-wellbore environment. In fractured reservoirs, fluid enters the reservoir at a few fractures intersecting the injector well, resulting in high fluid velocities near the borehole. The high fluid velocity can give rise to high impedance (entry losses) and turbulence of the well, resulting in lower injectivity (Chen and Wyborne, 2009). In Iceland, it is common practice to improve the injectivity of hot wells (typically >250°C) by injecting cold water into them for a few days. There has been no systematic study of these data and so the mechanism underpinning the stimulation is unclear. As a first step, we will undertake a systematic study of the Icelandic data that will be made available to us by ISOR and the Icelandic power companies through the IPGT agreement.

Module Leader

• Dr. Keith Evans

Team

• Dr. Benoit Valley
• Dr. Martin Ziegler
• Dr. Kathrin Menberg

The potential for the use of deep geothermal energy in Switzerland is enormous; however, its future development depends critically on the ability to assess and mitigate the nuisance, and potential economic risk posed by induced seismicity. Only if the seismic risk can be reliable assessed and limited to acceptable levels will geothermal energy contribute substantially to the Swiss energy mix of the future.

• How can we constrain the maximum possible earthquake and its dependence on site-specific parameters?
• How consistent is the seismic response of the underground, between sites and as a function of time?
• How can we improve the seismic imaging of fluid pressure- and shear-related porosity?

To address these challenges we propose below a series of five tasks that build upon the achievements of GEOTHERM:

1. Application of the b-value (Bachmann et al., 2011b) and stress-drop mapping techniques (Goertz- Allmann et al., 2011) applied to the Basel reservoir in GEOTHERM to a wider range of data sets in order to establish the systematics.
2. Where relevant, broaden the scope of data acquisition to include instances of injection-induced seismicity arising from activities other than EGSs, such as hydrothermal systems, liquid waste disposal, waterflood operations in enhanced oil recovery, and shale gas hydrofracture operations..
3. Application of time-sliced, tomographic imaging of P-wave, S-waves and Vp/Vs ratios to the Basel seismic data to recover images of the progression of porosity creation (related to fluid pressure migration) in the reservoir.
4. Application of full-waveform back-projection techniques, more commonly applied in geophysical exploration, to the Basel triggered and continuous data. The objective is to image the space-time evolution of the energy contribution of the tens of thousands of events too small to locate or even detect with ‘classical’ techniques.
5. Detailed spatio-temporal analysis of the seismicity on the individual structures within the Basel reservoir.

Answers to these questions will help constrain geo-mechanical models of permeability enhancement and numerical simulations.

Module Leaders

• Prof. Dr. Stefan Wiemer

Team

• Dr. Alba Zappone
• Dr. Aurélie Guilhem
• Dr. Pierre Dublanchet
• Dr. Dimitrios Karvounis
• Eszter Király
• Dr. Anne Obermann
• Dr. Toni Kraft
• Lukas Heiniger
• Dr. Arnaud Mignan
• Dr. Barbara Schechinger
• Dr. Laurentiu Danciu

In the context of geothermal energy, the development of future plants and the associated stimulation and production operations will pose numerous questions that need to be addressed with regard to:

• Systematic overview of the sources of risks or hazards that can cause harm or other consequences of interest
• Comparative risk assessment of the complete geothermal energy chain as well as its comparison to other technologies. This will enable the establishment of quantitative risk indicators, the identification of potential weak-points in the involved infrastructures, and the effects of geothermal energy on the overall risks of the future energy system
• Awareness of these risks by the public/specific stakeholder groups and related levels of acceptance of geothermal energy by the local population.

While deep geothermal energy is conceived as a renewable energy source with low CO2 emissions currently demanded and strongly supported by society, it is not known with certainty whether society will easily accept this type of energy infrastructure. The residual risk (Restrisiko) of potential earthquakes is one of many issues. A thorough understanding of accidental risks and the concerns and beliefs of these risks by the general public and specific stakeholder groups is required for a potential successful implementation of geothermal energy at large scale. Close collaboration between natural and social scientists and engineers is necessary to define and select relevant information and design a tailored communication strategy that addresses the different target populations. Communication of technical project information is not enough. Rather, a pro-active process of trust building and risk informed governance founded on an open exchange of views and concerns, and a respectful, transparent engagement is needed to prevent the lowering of acceptance levels. How all this can be achieved in the field of deep geothermal is an open and urgent question.

Module Leaders

• Dr. Michael Stauffacher
• Dr. Peter Burgherr

Team

• Dr. Matteo Spada
• Dr. Emilie Sutra
• Dr. Nora Muggli
• Dr. Corinne Moser

Enhanced Geothermal Systems (EGSs) depend upon the capability of engineering a heat exchanger in a fractured reservoir by enhancing the permeability of the fracture structures, perhaps with attendant creation of new fractures. This is accomplished by injecting fluid into the reservoir at sufficiently high pressure to weaken the fractures and promote shear failure and dilation. Shear failure is the rule because most rock masses support high levels of shear stress under ambient conditions.
From a modeling perspective, the ‘stimulation’ process is very complicated and involves continuous changes in the thermal, hydraulic and displacement fields all of which are coupled. Whilst there are several codes that can simulate heat extraction from a ‘built’ EGS under production conditions, there are no codes that we are aware of that can simulate the reservoir creation phase in 3-D paying adequate respect for the hydro-thermal-mechanical (H-T-M) coupling. The work in this module seeks to fill this gap, and provide a simulator that can be used to help improve our understanding of how a reservoir responds to pressure and temperature stimulation and high flow rates, which is a prerequisite for intelligent permeability creation and EGS operation strategies.

In EGS reservoirs, flow between boreholes and reservoir usually occurs at a few fracture zones, resulting in high fluid velocities that promote non-Darcy flow. The proposed work will extend the 3-D hydro-thermal (H-T) coupled EGS simulator developed in GEOTHERM to include non-Darcy flow and geomechanics. The result will be the first 3-D H-T-M coupled fractured reservoir simulator that can be applied to the ‘reservoir creation’ phase of EGSs.

Module Leader

• Prof. Dr. Patrik Jenny

Team

• Deb Rajdeep

The viability of EGS technology as an established energy source is dependent on our ability to run such installations reliably over periods of many years to decades with minimal servicing. There is little data available to demonstrate that this is possible, since all hot systems built to date have been circulated for at most a year (e.g. Hijiori, Japan).  Thus, empirical insights as to long-term trends in changing reservoir impedance and the rate of declining output temperature have not been established so far, and little is known regarding longer termperformance of hot (>200°C) reservoirs under production conditions.
Numerical simulation is currently the only option to extrapolate to such time scales and explore the long-term behavior and potential challenges.
The major expected problems during long-term operation are:

1. early breakthrough of cold water due to hydraulic shortcuts, potentially exacerbated by thermal contraction of cooled rock in areas of focussed fluid flow;
2. inefficient heat mining resulting from the hydraulic properties of the reservoir’s fracture network;
3. the long-term permeability changes due to fluid-rock chemical interactions leading to mineral dissolution and precipitation.

This Module is primarily concerned with point 3, quantifying the long-term changes that take place in fracture permeability and their implications for points 1. and 2.

The focus here is on geochemical (i.e. fluid-rock interaction) changes since these are the least-well understood. So far, theoretical studies of the effects of fluid-rock interactions have not progressed much beyond basic porous media considerations, and it is the main goal of Module 5 to substantially increase the realism of how the reservoir itself, and processes acting therein, are being represented in numerical simulation.

Module Leader

• Dr. Thomas Driesner

Team

• Dr.Julian Mindel
• Dr.Philipp Weis
• Dr.Denis Zezin
• Samuel Scott

Based on preliminary results obtained in GEOTHERM, the goals of the project will therefore be to further develop the methodology for the design of geothermal energy conversion systems and in particular to study its integration in cities. The project will concern the development of a decision support tool to study the integration of geothermal energy usage in cities. The tool will include :

1. geographic information to geo-localize and characterize the demands and the available geothermal resources;
2. a data base of energy conversion technologies for both heat and power production;
3. a comprehensive thermodynamic and life cycle environmental impact assessment tool of selected systems designs;
4. a design tool based on optimization and process integration techniques to define the best energy conversion system in sizes and operating strategy.

The design method will consider the overall lifespan of the well and include the possible use of storage systems and an uncertainty analysis to assess that impact of the uncertain parameters on the decision of integrating geothermal energy in cities.

Module Leader

• Dr. Francois Maréchal

Team

• Prof. Liesse Laloui
• Dr.Laurent Tacher
• Dr. Peter Bayer
• Stefano Moret
• Ramannunui Menon
• Brigitte Fayet
• Rosa-Ana Turielle

Hirschberg S., Wiemer S., Burgherr P. (2015) Energy from the earth: Deep geothermal as a resource for the future? TA-Swiss, Bern, Switzerland, pp. 220-251.

Hillers G., Husen S., Obermann A., Planès T., Campillo M., Larose E. (2015) Noise based monitoring and imaging of aseismic transient deformations induced by the 2006 Basel reservoir simulations, Geophysics, 80, 4, doi: 10.1190/GEO2014-0455.1.

Obermann A., Kraft T., Larose E., Weimer S. (2015) Potential of ambient seismic noise techniques to monitor reservoir dynamics at the St. Gallen geothermal site (Switzerland), JGR , doi: 10.1002/2014JB011817

Preisig G.,Eberhardt E., Gischig V., Roche V., van der Baan M., Valley B., Kaiser P.K., Duff D., Lowther R., (2015) Development of connected permeability in massive crystalline rocks through hydraulic fracture propagation and shearing accompanying fluid injection. Geofluids, 15, 321-337, doi.org/10.1111/gfl.12097.

Rivera J. A., Blum P., Bayer P. (2015) Analytical simulation of groundwater flow and land surface effects on thermal plumes of borehole heat exchangers. Applied Energy, 146, 421-433.

Stauffacher M., Muggli N., Scolobig A., Moser C. (2015) Framing deep geothermal energy in mass media: the case of Switzerland. Technological Forecasting and Social Change DOI: 10.1016/j.techfore.2015.05.018.

Zezin D, Driesner T, Sanchez-Valle C. (2015) Volumetric Properties of Na2SO4–H2O and Na2SO4–NaCl–H2O Solutions to 523.15 K, 70 MPa; J. Chem. Eng. Data, 2015, 60 (4), 1181–1192; DOI: 10.1021/je501152a.

Deichmann N., Kraft T., Evans K.F. (2014) Identification of faults activated during the stimulation of the Basel geothermal project from cluster analysis and focal mechanisms of the larger magnitude events, Geothermics, 52, 84-97.

Kraft T., Deichmann N. (2014) High precision relocation and focal mechanism of the injection induces seismicity at the Basel EGS, Geothermics, 52, 59-73.

Hillers G., Husen S., Obermann A., Planès T., Campillo M., Larose E., (2015) Noise based monitoring and imaging resolve reservoir dynamics associated with the 2006 Basel injection
experiment, Geophysics, in press.

Hingerl F.F., Kosakowski G., Wagner T., Kulik D.A., Driesner T. (2014) GEMSFIT: a generic fitting tool for geochemical activity models. Computational Geosciences 18, 227-242.

Hingerl F.F., Wagner T., Kulik D.A., Thomsen K., Driesner T. (2014) A new aqueous activity model for geothermal brines in the system Na-K-Ca-Mg-H-Cl-SO4-H2O from 25 to 300°C. Chem. Geol. 381, 78-93.

Moret S., Bierlaire M. and Maréchal F. (2014) Robust Optimization for Strategic Energy Planning, Technical report.

Obermann A., Kraft T., Larose E., Wiemer S. (2015) Potential of ambient seismic noise techniques to monitor the St. Gallen geothermal site (Switzerland), J. Geophy. Res., in press

Spada M., Sutra E., Wolf S., Burgherr P. (2014) Accident Risk Assessment for Deep Geothermal Energy Systems. In: Nowakowski, T., Mlynczak, M., Jodejko-Pietruczuk, A., Werbinska-Woiciechowska, S. (Eds.), Safety and Reliability: Methodology and Applications. Taylor and Francis Group, London UK.

Weis P., Driesner T., Coumou D., Geiger S. (2014) Hydrothermal, multiphase convection of H2O-NaCl fluids from ambient to magmatic temperatures: a new numerical scheme and benchmarks for code comparison. Geofluids 14 (3), 347-371; DOI: 10.1111/gfl.12080.

Zezin D., Driesner T., Sanchez-Valle C. (2014) Volumetric Properties of Mixed Electrolyte Aqueous Solutions at Elevated Temperatures and Pressures. The System KCl–NaCl–H2O to 523.15 K, 40 MPa, and Ionic Strength from (0.1 to 5.8) mol•kg–1. Journal of Chemical and Engineering Data 59, 736-749.

Carter, T. G., Valley, B. (2013) Application of fault stability analysis techniques for design of deep engineering projects. In: ARMA 2013, 47th US Rock Mechanics / Geomechanics Symposium.

Driesner T. (2013) The Molecular-Scale Fundament of Geothermal Fluid Thermodynamics. Reviews in Mineralogy and Geochemistry 76, 5-33.

Gischig, V., Wiemer, S. (2013) A stochastic model for induced seismicity based on non-linearpressure diffusion and irreversible permeability enhancement, Geophys. J. Int., doi: 10.1093/gji/ggt164, PP 21.

Kaiser, P. K., Valley, B., Dusseault M. B. and Duff, D. (2013) Hydraulic Fracturing Mine Back Trials – Design Rational and Project status. In: Effective and sustainable hydraulic fracturing, Bunger, A. P., McLennan, J. and Jeffrey, R. (Eds). p. 877-891. Intech, Croatia.

Evans K.F. (2015) Thermal stimulation of boreholes, Geotherm-2 semi-annual meeting, Zürich, 4 Feb. 2015.

Karvounis D.C., Wiemer S. (2015) Monte Carlo Simulations of EGS Stimulation Phase with a 3-D Hybrid Model, presented in the 1st Schatzalp Workshop on Induced Seismicity, Davos, Switzerland, 10-13 March 2015.

Karvounis D.C. , Wiemer S. (2015) Decision Making Software for Forecasting Induced Seismicity and Thermal Energy Revenues in Enhanced Geothermal Systems, Submitted to Proceedings World Geothermal Con-gress 2015. Melbourne, Australia, 19-25 April.

Király E., Zechar J D., Gischig V., Karvounis D., Heiniger L., Wiemer S. (2015) Modeling and Forecasting In-duced Seismicity In Deep Geothermal Energy Projects. Submitted to Proceedings World Geothermal Con-gress 2015. Melbourne, Australia, 19-25 April.

Moret S., Gerber L., Amblard F., Peduzzi E., Maréchal, F. (2015) Geothermal Energy and Biomass Integration in Urban Systems: a Case Study. 40th Workshop on Geothermal Reservoir Engineering, Stanford Universi-ty, Stanford, California, USA.

Obermann A., Kraft T. , Larose E., Wiemer S. (2015) Potential of ambient seismic noise techniques to monitor the St. Gallen geothermal site , AGU S51A-4441, AGU fall meeting December 2014

Obermann, A. (2015) Monitoring with ambient noise. Berkeley, Stanford, USGS, San Diego; 1st april2015.

Valley, B., K. F. Evans (2015), Estimation of the stress magnitudes in Basel Enhanced Geothermal System, paper presented at World Geothermal Conference 2015, International Geothermal Association, Melbourne, Australia, 19-24 April.

Ziegler M., Valley B., Evans K.F. (2015) Module 1: EGS reservoir characterisation and geomechanics, Geotherm-2 semi-annual meeting, Zürich, 4 February 2015.

Ziegler M., Valley B., Evans K.F. (2015). Characterisation of natural fractures and fracture zones of the Basel EGS reservoir inferred from geophysical logging of the Basel-1 well. Proceedings World Geothermal Congress. International Geothermal Association, Melbourne, Australia, 19-25 April 2015.

Bayer P., Menberg K., Blum P. (2014) Thermal footprints in groundwater of central European cities. – AGU Fall Meeting, 15-19 December, San Franciso.

Evans K.F. (2014) Reservoir creation: lessons learned from past projects & strategies for improvement, TA-Swiss Project Workshop, ETH Zürich, 4th March.

Evans K.F. (2014) SCCER-SoE Roadmap for developing Deep Geothermal resources of Switzerland for elec-tricity generation, IPGT Steering Committee meeting, Gerzensee, Bern, 5 June 2014.

Evans, K.F. (2014) Stimulation and zonal isolation group activity summary, IPGT Steeriung Committee meet-ing, Gerzensee, Bern, 5 June 2014.

Karvounis D.C., Gischig V., Wiemer S. (2014) EGS Probabilistic Seismic Hazard Assessment with 3-D Discrete Fracture Modeling: PROCEEDINGS, Thirty-Ninth Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California, February 24-26.

Karvounis D.C., Gischig V., Wiemer S. (2014) Towards a Real0Time Forecast of Induced Seismicity for Enhanced Geothermal Systems: PROCEEDINGS, ASCE, Shale Energy Engineering Conference, Pittsburgh, Pennsylvania, July 21-23.

Király E., Gischig V., Karvounis D.C., Wiemer S. (2014) Validating Models to Forecasting Induced Seismicity Related to Deep Geothermal Energy Projects. PROCEEDINGS, Thirty-Ninth Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California, February 24-26.

Király E., Gischig V., Karvounis D.C., Heiniger L., Wiemer S. (2014) Forecasting Induced Seismicity In Deep Geothermal Energy Projects. Geophysical Research Abstracts Vol. 16, EGU2014-12511, EGU General Assembly April 27-May 02.

Mindel J. and Driesner T. (2014) Reactive transport in 3D models of irregularly fractured rock masses. AGU Fall Meeting 2014, abstract H33B-0797

Moret S. (2014) Geothermal energy integration in urban systems, CCES Conference 2014 PART II, 26th February.

Moret S., Bierlaire M., Maréchal, F. (2014) Robust optimization for strategic energy planning (2014b) 1st Eu-ropean Conference on Stochastic Programming and Energy Applications (EuroCSP 2014), Paris, France.

Moret S., Codina Gironès, V., Maréchal, F., Favrat, D. (2014) Swiss-energyscope.ch: a Platform to Widely Spread Energy Literacy and Aid Decision-making. PRES 2014 - 17th Conference Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction, Prague, Czech Republic, 2014. The developed platform is publicly available at the link http:// energyscope.ch.

Rajdeep D., Jenny P. (2014) Modeling of Failure Along Predefined Planes in Fractured Reservoir, Proceedings, 39th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, February 24 - February 26, 2014 SGP-TR-202.

Rajdeep D., Jenny P. (2014) Modeling of Failure Along Predefined Planes in Fractured Reservoirs, Proceedings, 39th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, February 24 26. SGP-TR-202.

Spada M., Sutra E., Wolf S. & Burgherr, P. (2014). Accident Risk Assessment for Deep Geothermal Energy Systems. European Safety and Reliability Conference, ESREL 2014, 14-18 September 2014, Wroclaw, Poland.

Sutra E., Spada M., Wolf S., & Burgherr P. (2014). Comparative Risk Assessment for Hydraulic Fracturing in Shale Gas and Deep Geothermal Systems. 23rd SRA-Europe conference, Istanbul, Turkey, 16-18 June.

Valley B. (2014) Underground injection experiment in deep mine, IPGT Steeriung Committee meeting, Gerzen-see, Bern, 5 June 2014.

Valley B., Evans K. F. (2014) Geotherm-2 Module-1 Update, Geotherm-2 Semi-Annual Meeting, ETH-Zürich, 15th January.

Valley B., Evans, K.F. (2014) Borehole-based measurements for reservoir characterisation, TA-Swiss Project Workshop, ETH Zürich, 4th March.

Valley B, Evans K.F. (2014) Preliminary assessment of the scaling relationships of in-situ stress orientation variations indicated by wellbore failure data. In: Alejano LR, Perucho A, Olalla C, Jimémez R, editors. EUROCK 2014: Rock Engineering and Rock Mechanics: Structures in and on Rock Masses. Vigo, Spain, 27-29 May

Valley B., Evans K.F. (2014).Physical linkage between power-law scaling relations for stress, microseis-micity (b-value) and fracture length distributions, Project Image meeting, Luzern, 20-21 November 2014.

Valley B., Jalali M.R., Ziegler M., Evans K.F. (2014) Constraining DFN characteristics for deep geothermal project considering the effects of fractures on stress variability. First Int. Conf. on Discrete Fracture Network Engineering, Vancouver, 19-22 October.

Vogler D., Amann F., Bayer P., Brauchler R. (2014) A Numerical Study on Small-Scale Perme-ability Crea-tion Associated with Fluid Pressure Induced Inelastic Shearing. – AGU Fall Meeting, San Franciso, 15-19 December.

Vogler D., Bayer P., Brauchler R., Amann F. (2014) A numerical study on small-scale perma-bility creation associated with fluid pressure induced inelastic shearing. – Computational Methods in Water Resources, 10th – 13th June, Stuttgart.

Weis P., Driesner T., Coumou D., Geiger S. (2014) Hydrothermal, multiphase convection of H2O-NaCl fluids from ambient to magmatic temperatures: a new numerical scheme and benchmarks for code comparison. Geofluids 14 (3), 347-371; DOI: 10.1111/gfl.12080.

Ziegler M., Valley B., Evans K.F. (2014) Module 1: EGS reservoir characterisation and geomechanics, Geotherm-2 semi-annual meeting, Lausanne, 8 July 2014.

Evans, K.F. (2013) Identification of fracture zones from borehole logs, Presentation at meeting with GeoEnergy-Swiss, Zürich, 15 July.

Evans, K.F. (2013) Enhanced Geothermal Systems (EGS) - Experience to Date and Lessons Learned, ZLG Certif-icate of Advanced Study short course in ‘Deep Geothermal Energy - Prospection, Exploitation and Reservoir Management’ , ETH-Zürich, 2-6 September.

Evans, K. F .(2013) Petrothermal Reservoir Creation, Presentation to the TA-Swiss Begleitgruppe for the study, “Energie aus dem Innern der Erde: Tiefengeothermie als Energieträger der Zukunft?”, Bern, 19th November.

Moret, S. (2013) Presentation of Geotherm II and Lausanne case-study plan, city of Lausanne, 25th September.

Stauffacher, M. (2013) Geothermal between “good” renewable energy and “bad” large centralized infrastructure. 11th Conference of the European Sociological Association, Turin, August 28-31.

Valley, B., Evans, K. F. (2013) Geotherm-2 Work Plan, Geotherm-2 kick-off meeting, ETH-Zürich, 11th July.

Valley B. (2013) La caractérisation des contraintes mécaniques pour les projets géothermiques profonds, Leçons probatoire, Université de Neuchâtel. 11th June.

Valley, B. (2013) Characterization of geothermal reservoirs using well logging data, ZLG Certificate of Advanced Study short course in ‘Deep Geothermal Energy - Prospection, Exploitation and Reservoir Management’ ETH-Zürich, 2-6 September.

Valley, B. (2013) Fracturing and stress characterisation of deep gepthermal systems, 2nd European Geothernal Workshop, Strasbourg, 24-25 October.