New research project examines storage options for CO2 in former natural gas reservoirs

View of the underground laboratory in the research and teaching mine.
Together with partners from research and industry, a team from TU Bergakademie Freiberg is investigating how carbon dioxide from exhaust gases could be safely stored under the earth's surface in the future.

The researchers are keeping an eye on former natural gas fields under the North Sea. In the future, CO2 from industrial emissions and the atmosphere could be stored in this porous rock. This could not only reduce the greenhouse gas it could also help to stabilize the underground reservoirs after the end of natural gas production.

Over the next three years, the researchers will be investigating how this concept can be implemented in an international joint project by the Norwegian research institute SINTEF together with the TU Bergakademie Freiberg, the Universities of Cambridge (UK) and Utrecht (Netherlands), and the industrial partners Wintershall Dea, Shell and Equinor. The European Union is funding the ACT-RETURN project with a total of 7,41 million euros.

Focus on two central questions

The pressure in the underground reservoirs is very low at the end of the natural gas production. This because of the special thermodynamic properties of CO2 there is always the risk of a phase transition occurring at the beginning of CO2- injection through a borehole, for example from liquid to gaseous CO2 with a subsequent two-phase CO2- flow. This leads to enormous fluctuations in pressure and temperature, which in turn is associated with considerable risks for the integrity of the well (safety problem) as well as for the CO2- injection behavior (economic problem),” explains Prof. Mohd Amro.

"Another challenge is that there are currently no computer-aided models that would be able to depict the complex flow behavior of CO2 with sufficient accuracy," adds the head of the Institute for Drilling Technology and Fluid Mining. Safety-related and economic risks can therefore not be recorded and the necessary operational optimizations cannot be carried out. This is where the research at the institute comes in: "Together with our industrial partner Wintershall Dea AG, we are developing numerical and simultaneous solutions based on existing software that needs to be optimized."

The team obtains the data required for the software solution in a first step with the help of investigations in the underground laboratory in the research and teaching mine of TU Bergakademie Freiberg. There is a constant temperature all year round. In a special reactor, the researchers can also simulate the pressure in the investigated deposit and thus analyze the influence of the two factors on the rock samples with the injected CO2 in the order of magnitude of around 100 milliliters. "The data collected in Freiberg provide the project partners with an important basis for testing the project in real deposits," says Prof. Mohd Amro.

Future-oriented research field for geostructural and storage technology

"As the project that has just been approved shows, interesting and future-oriented research questions in the field of geo-flow and storage technology arise even after the so-called end of the petroleum age," says the project manager. Ph.D. student Martin Kirch supports Prof. Support Mohd Amro in the implementation of the project over the next three years. "Our results will also flow into the application-oriented training of the students."

Fragen beantwortet / Contact: 
Prof. Dr. Mohd Amro, Phone: +49 3731 39-2542; E-Mail: Mohd.Amro@tbt.tu-freiberg.de