The ISC Experiment is a geothermal research project initiated by the SCCER-SoE (Swiss Competence Centre for Energy Research – Supply of Electricity) and scientifically directed by the ETH Zurich.

The primary goal is to improve our understanding of geomechanical processes underpinning permeability creation during hydraulic stimulation and related induced seismicity as well as to evaluate the efficiency of the generated underground heat exchanger. The experimental site is located in the southern part of the GTS between the VE-Drift and the Main Access Tunnel. In this area, three shear-zones are present dipping south to south-east at steep angles.

The project tasks are grouped in three phases.

Pre-Stimulation Phase (2015/16)

  • Drilling and investigation of 15 boreholes
  • Hydraulic & geophysical characterisation 
  • Determination of the stress regime -> derive slip tendencies and fracture reactivation pressures
  • Installation of seismic monitoring network in galleries
  • Installation of monitoring systems for pore pressure, temperature, strain

Stimulation Phase (2017)

  • Hydraulic stimulation of existing shear-zones
  • Stimulation of newly hydraulic fractured rock 
  • Real-time monitoring of near-field effects: seismic emissions, displacement and changes in pressure and strain.

Post-Stimulation Phase (2017)

  • The aim of the post-stimulation phase is to investigate and document the changes in hydraulic and geophysical properties provoked by the previous stimulation activities.
  • Circulation phase: study of thermal effects on fracture flow, efficiency of newly created heat exchanger


ICS simulation phases


SCCER SoE geo-energy 

Demo-1: Flagship stimulation experiment in the deep underground laboratory

ISC Project description 

ETH Globe Magazine article: The rock crackers 


ISC Boreholes


Primary purpose

Acitivities / Instrumentation

Number of


Geophysical investigation borehole

  • Geophysical characterization using GPR and active seismics
  • Crosshole tomography
  • Hydraulic characterization using GPR monitoring of salt tracer tests



Strain monitoring

  • Fiber-optics  (FBG’s distributed)
  • temperature monitoring



Injection borehole

  • Injection (stimulation)
  • Hydraulic (multi-) packer tests
  • Tracer tests (dye, salt, DNA)



Pore pressure monitoring borehole

Multi-interval pore pressure and temperature monitoring in shear-zones near to the intersection points of INJ-boreholes



Stress measurement borehole

  • Over-coring stress measurements
  • HF and HTPF tests


All boreholes were cored, geophysically logged and hydraulically characterized using multi-packer systems.

ICS layout 001

Source: Micro-seismic monitoring during hydraulic-shearing experiments at the Grimsel Test Site
Villiger,L,   Gischig,V.,  Doetsch, J, Krietsch, H., Jalali, M., Amann, F., Evans, K., Valley, B., Wiemer, S. Schatzalp Workshop on Induced Seismicity, 2017.

ICS Geophone array

Geophone array and high precision tilt meter (foreground) in the VE-Tunnel to monitor seismic micro-events and ground movement during hydraulic stimulation in the ISC Injection Boreholes.


ICS Seismic investigation of GEO boreholes

Seismic investigation of GEO-boreholes

ICS Hydraulic stimulation works

Hydraulic stimulation works

ICS Assembling multi packer system

Assembling multi-packer system for hydraulic characterisation of boreholes 

ICS Seismic sensor

Seismic sensor placed in recess of tunnel wall