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