The pilot CO2 test injection project in Trüllikon, Switzerland: project outline and first simulation results

Switzerland is currently expanding renewable energies and aims to initiate carbon capture and storage (CCS), which is necessary to meet national and international climate change goals. The pilot CO₂ test injection planned at the Trüllikon site in northern Switzerland (CITru project) would be the first initiative for the storage of CO₂ underground in Switzerland. The Trüllikon site was investigated in detail in the context of the Swiss radioactive waste management program. Hydraulic tests carried out in the TRU1-1 well have shown that the hydraulic properties of the Upper Muschelkalk layer (Stamberg Member) and the presence of a low-permeability cap rock (Bänkerjoch Formation) are generally promising to enable the initiation, planning, and implementation of a small-scale CO₂ demonstration injection.

In the first phase of the project, additional site investigations are planned, such as a seismic survey, a review of the previously conducted hydrotests, and a detailed risk analysis. An important contribution to the initial planning of the project are numerical simulations to show the theoretical feasibility of a CO₂ test injection, i.e., the estimation of subsurface pressures, temperatures, and flow parameters during a potential small-scale CO₂ injection. Here, we show an outline of the project focusing on preliminary numerical modeling results using advanced multiphase flow simulation tools. The simulations are intended to show, for instance, the pressure and temperature changes near the borehole, effects on nearby faults and the expected expansion of dissolved and undissolved CO₂ in the reservoir. The results of the numerical simulations will help to constrain the expected reservoir and well behavior during the envisioned injection test and could be used to optimize injection strategies and monitoring techniques.