Developing laboratory expertise to foster CO2 ground storage

Carbon capture and storage (CCS) technologies can contribute to reaching these goals. This technique has received increasing attention since carbon dioxide (CO₂) was identified as a major greenhouse gas. One of the most practical CCS solutions is CO₂ sequestration. The principle is to remove CO₂ from the atmosphere and inject it into deep underground formations where it is trapped by a caprock formation that overlies the reservoir, allowing more infrared radiation to escape into space.

The Laboratory of Soil Mechanics (LMS) at EPFL is contributing to important research in this field. For example, LMS is exploring the behavior of the caprock when a CO₂ -rich fluid is injected. To ensure this barrier remains under stable conditions to prevent the propagation of CO₂ from the reservoir to the surface, the transport properties and sealing capacity of the caprock need to be determined. Through laboratory testing and numerical analysis, the LMS is contributing to a full understanding of the response of the potential caprock material in Switzerland. It is a multiphysical problem with strong couplings to thermo-hydro-chemo-mechanical processes which must be assessed. To do so, advanced experimental analysis is required to investigate the coupled response of the caprock material and reproduce it as accurately as possible in an actual field situation. However, testing these responses remains challenging as the CO₂ must be injected in a liquid or supercritical form whilst representative pressures and temperatures must be simulated correctly to ensure a representative sample state.

At the LMS a variety of special testing devices allow representative testing under such conditions. LMS has developed a temperature control chamber and different high-pressure devices that enable CO₂ injection and hydromechanical testing for the evaluation of transport properties and the sealing capacity of the caprock. Other properties that can be evaluated at the laboratory include the transport properties of the caprock which is very slow and requires high-resolution measurement as well as the reservoir injectivity and chemical impact on the hydromechanical response. Additionally, LMS employs high-resolution x-ray micro-CT for the analysis of local modifications in the microstructure of both caprock and reservoir materials, which are highly heterogeneous.

Combining these advanced testing opportunities with a high level of expertise allows us to investigate this coupled multiphysical problem and to contribute to the potential future implementation of CO₂ sequestration. For instance, it allows LMS to work on optimizing the injection of high volumes of CO₂ while avoiding high overpressures that might trigger induced seismicity.

Switzerland has yet to decide what steps it will take to sequester CO₂. However, on 20 July 2021, Switzerland and Iceland signed a statement of intent to jointly support and develop negative-emission technology, which includes carbon storage. The research done over the past years has shown that there is enough underground capacity in Switzerland to store large amounts of CO₂, primarily in the Swiss Plateau, from Fribourg to Zurich, and therefore there is a large potential for this technology to contribute to reducing Switzerland’s CO₂ emissions.

CO₂ sequestration is not the only field where LMS excels in evaluating advanced and sometimes unconventional engineering scenarios. Thanks to advanced testing facilities, which are designed and manufactured in our laboratory, and our expertise and experience based on long engagements with civil engineering in difficult or environmentally sensitive urban areas, even the most complicated loading scenarios can be simulated, allowing the laboratory to find solutions for some of the most advanced geotechnical challenges around the world.