Task 1.2: Reservoir modeling and validation

Research partners: Swiss Federal Institute of Technology in Zurich (ETHZ), École Polytechnique Fédérale de Lausanne (EPFL), University of Geneva, University of Bern, Università della Svizzera Italiana, Paul Scherrer Institute (PSI), University of Applied Sciences Rapperswil (HSR)

Research objectives

Geothermal and CO2 storage reservoirs in the deep underground experience high temperatures, pressures, and stresses, and are intersected by complex patterns of natural fractures. As a result, reservoir creation and operation requires understanding complex – and often coupled – interactions of thermal, hydraulic, rock mechanical, and (geo)chemical (THMC) processes. As direct observation opportunities at depth are very scarce (very few relevant sites exist) and very limited in their scope (e.g., fracture distributions can only be mapped on borehole walls), numerical simulation and analogue experiments on different scales are key technologies to improve our ability to quantify these processes and their interactions. Key objectives of Task 1.2 are:

  • Develop the next generation of numerical simulation tools: Although current simulation tools allow obtaining key insights into coupled THMC processes, they are unable to address them in large “geologically realistic”, i.e., geometrically complex, large, 3D representations of fractured reservoirs. Task 1.2 aims at overcoming these limitations, in close collaboration with the SCCER-SoE Modeling Facility (Task 4.3). Activities started with a review of existing numerical modelling expertise and developments efforts in Switzerland and worldwide, code validation and benchmarking studies in close collaboration with already existing benchmarking activities with Swiss participation within IPGT etc. Current activities relate to identifying the best software development strategies and strengthening the interaction between those partners who develop cutting-edge research codes and the computational science personnel from the SCCER-SoE Modelling Facility. Research codes are often of high scientific quality but rather poor in performance and software design. Task 1.2 addresses both aspects. Collaboration with Task 4.3 allows conversion to professional quality software modules with modular interfaces and numerically robust and efficient couplings. Professional software development, testing and validation environments are being set up. For the 2017-2020 phase, additional emphasis will be put on user-friendliness of the codes to unleash their power to researchers and practitioners involved in pilot and demonstration projects (Task 1.3), and to integrate them with the exploration and data structure activities of Tasks 1.1 and 1.4.
  • Establish and strengthen a comprehensive and coordinated experimental research program on very different scales ranging from conventional indoor to large-scale underground laboratories (e.g., Grimsel and Mt. Terri) allow studying mechanical reservoir creation processes, argillaceous caprock leakage and chemical fluid-rock interactions to be investigated. In rock deformation laboratories, rock mechanical processes such as fracture generation and/or fracture slip during hydraulic stimulation are being investigated under in situ temperature-pressure-stress conditions but on scales of centimeters only. On the contrary, large-scale underground laboratories allow studying the in situ properties and behavior of large fractures but at ambient temperatures and moderate pressures and stresses only. However, using the experimental data will form the basis for developing invaluable constitutive relationships for process couplings that can be applied in actual reservoir creation and operation processes. The experimental data will also serve as benchmarks for numerical model validation, which can then be used to bridge the different scales and parameter ranges by means of numerical simulation.

Current projects

GEOTHERM-2 conducts cross-disciplinary research towards the development of Enhanced Geothermal Systems (EGS). It represents the second phase of GEOTHERM (2009-2012), a comprehensive program of basic research on key aspects of Enhanced Geothermal Systems (EGS). GEOTHERM-2 conducts cross-disciplinary research targeted to the development of Enhanced Geothermal Systems (EGS). The research addresses aspects concerning the geomechanical characterization of reservoirs, the numerical simulation of a reservoir creation, the long term effects of geochemical reactions on permeability and heat extraction, the assessment and management of the induced seismicity risk, the social acceptance and comparative assessment of the risks inherent to an EGS project, and the analysis of geothermal energy usage in cities, with the case study of Lausanne.

Research partners: Swiss Seismological Service (SED) at ETHZ, Laboratory for Energy Systems Analysis (LEA) at PSI

Source of funding: Competence Center Environment and Sustainability (CCES) and Competence Center for Energy and Mobility (CCEM) at ETHZ, Swiss Federal Office of Energy (SFOE)

Duration: May 2013 to April 2016

Project website

COTHERM started in 2012 as a synergistic collaboration with four sub-projects to advance our understanding of the fundamental geological, chemical, and physical processes governing the sub-surface structure and dynamics of geothermal systems. Our follow-up project will address fundamental questions regarding a new type of geothermal resources (so-called “supercritical resources”) that were recently discovered at Krafla Volcano, Iceland. Supercritical resources bear the potential to boost geothermal power production by up to an order of magnitude per well.

Research partners: Institute of Geochemistry and Petrology (IGP) at ETHZ, Paul Scherrer Institute (PSI), University of Iceland, Iceland GeoSurvey (ISOR)

Source of funding: Swiss National Science Foundation (SNSF) Sinergia

Duration: September 2015 to August 2016

Project website

Permeability is the decisive reservoir property for the economic success of geothermal operations as it determines the flow rates that can be achieved when circulating fluid to mine heat from the reservoir. However, at the depth of deep geothermal reservoir targets, permeability is typically too low for commercial circulation rates and therefore requires enhancement by (hydraulic) stimulation. There is currently no quantitative theory that can predict by how much reservoir permeability may be enhanced during stimulation at a given site. This uncertainty is one of the major investment risks in the future development of deep geothermal energy in Switzerland. In addition, seismicity induced by hydraulic stimulation is the biggest technical and societal acceptance risk. Our project develops and applies novel numerical simulation techniques for the quantification of permeability enhancement during hydraulic stimulation, its spatial evolution during reservoir development, and the seismicity-related processes of fault slip during stimulation.

Source of funding: Swiss National Science Foundation (SNSF), National Research Programme 70

Research partners: Institute of Geochemistry and Petrology at ETHZ, Department of Earth Sciences (D-ERDW) at ETHZ, Università della Svizzera italiana (USI), University of Neuchâtel

Duration: November 2014 to October 2017

Project website

The chair "Gaz Naturel" aims at reproducing the thermo-hydro-chemo-bio-mechanical THCBM coupled behaviour of the reservoir materials during CO2 injection and storage in all time scales, in particular the formulation of constitute model and of the mathematical/numercial model for the coupled behaviour. Its implementation in a FE code and the experimental investigations will be processed for the material characterization and validation of the numerical tool.

Source of funding: Petrosvibri SA

Research partners: EPFL, Gaznat SA, Holdigaz SA

Duration: 2012 to 2020

Project website

The current suite of THMC models are limited because the wide range of timescales associated with the processes underlying fluid-injection in the earth result in numerically cumbersome calculations at insufficient resolution. The complex and coupled processes associated with fluid-injection (fracture, fluid flow, heat flow, and chemical reactions) require a new generation of numerical algorithms designed for High Performance Computing (HPC). A primary focus of the numerical modeling group at the University of Neuchatel is to develop the next generation of simulators that can model the nucleation, growth, and coalescence of numerical fractures that evolve in response to far-field stresses, and stress perturbations arising from poroelastic / thermoelastic stresses and in response to fracture network itself. This network provides the principal pathways for fluid flow, and thus heat flow, allowing simulations of the injection processes, and for studying the long-term viability of a geothermal resource. Our approach is design algorithms optimized for Graphics Processing Unit (GPU) clusters, with the aim of high-resolution and computationally fast simulations.

Source of funding: University of Neuchâtel

Research partners: University of Neuchâtel

Duration: November 2014 to October 2018

The Swiss Federal Energy Strategy 2050 calls for scientific research to support industry's endeavours to (1) generate electricity from geothermal energy and (2) develop deep geological sites for permanent, safe storage of CO2, such that gas-fired power stations may be operated in an environmentally sustainable way. At present, there are no proven sites for these technologies in Switzerland. This project will therefore support industry's first steps towards these aims, namely the assessment of geothermal and gas-storage resources, the exploration for promising drilling sites and the characterization of potential heat- and gas-storage reservoirs. The project will elaborate exploration guidelines and methodologies to lower the risk of failure of exploration drilling.

The research is organized into four subprojects, with overlapping participation of 17 scientists from the disciplines of geology, geochemistry, structural geology, geophysics and petrophysics at the University of Bern, the University of Lausanne and ETH-Zurich, plus in-kind collaboration from industry personnel. In addition to research expenses, we request from NRP70 the salaries for a research position for each subproject, i.e. 3 doctoral students (3 years each) and 1 post-doctoral researcher (2 years).

  • Subproject A will analyse drill core from wells in Switzerland's main saline aquifer (Upper Muschelkalk) and reconstruct the geological processes that led to formation or destruction of its porosity and permeability. This conceptual understanding will be used to create a 3D static model of the reservoir properties, to serve as a guide in commercial exploration for sites for geothermal electricity production and CO2 sequestration. The potential for these energy applications will mapped into the model, to provide improved estimates of geo-energy resources and a planning tool for decision-makers at local, canton and federal levels.
  • Subproject B will focus on a >20 km long, hydrothermally active fault that outcrops in granite on the Grimsel Pass (Aar Massif). As well as being a geothermal system in its own right, this fault is an analogue of water-conducting faults in the basement of the Swiss Molasse Basin (SMB), which are targets of geothermal exploration. Surface outcrops will be mapped and a shallow borehole will be drilled through the fault to permit construction of a 3D static model of its geometric and hydraulic properties. This model will serve to assess the geothermal potential of the northern Alpine margin, it will provide exploration companies with a template for hidden faults in the SMB with which they can interpret seismic surveys and plan hydraulic stimulation, and it will provide a realistic framework for dynamic modelling of deep geothermal reservoirs conducted by a parallel subproject of the NRP70 Umbrella cluster.
  • Subproject C will conduct a detailed geophysical survey of the Grimsel Pass borehole. Geophysical logging of the borehole will characterize the hydraulics of the Grimsel fault, for input into the 3D static model. Surface-to-borehole seismic experiments will use the Grimsel fault as a test case to determine whether seismic methods can remotely detect permeability in fractured crystalline rocks. The results will be used to elucidate the fundamental relations between seismic attenuation and effective permeability of fractured rocks, using a comprehensive poro-elastic approach involving advanced numerical simulations. Corresponding field workflows for this new methodology will be made available to the exploration industry.
  • Subproject D will conduct cutting-edge laboratory measurements and experiments on core samples to determine the petrophysical properties of the Upper Muschelkalk and Grimsel Fault reservoirs, and to explore in general the relationship between the effective permeability of fractured rocks and the attenuation of seismic waves and electrical resistivity. Measurements of electrical conductivity, elastic properties, seismic attenuation and permeability will be made in new apparatus capable of reaching deep reservoir conditions (T = 250 °C, Prock = 100 MPa and Pfluid = 50 MPa). The results will be used to support subprojects A, B and C, and the developed methodologies will be made available to industry.

Source of funding: National Research Programme 70

Research partners: Institute of Geological Sciences at the University of Bern, Geological Institute at ETHZ, Faculty of Geosciences and Environment at the University of Lausanne

Duration: October 2014 to September 2018

Project website