Monitoring of CO₂ plume expansion by combining active and passive seismic data – phase II

The project builds on results from CO₂CAP (616065). CO₂CAP has been a collaboration between the North American Illinois State Geological Survey (ISGS) and Norwegian NORSAR / SINTEF to develop new and effective CO₂ monitoring technologies. CO₂CAPII continues the bilateral cooperation between ISGS and NORSAR / SINTET developed in CO₂CAP.

In addition, the project has brought in Norwegian industrial partners at Northern Lights. The CO₂CAP project provided detailed results of seismicity at Decatur. These results provided the basis for demonstrating how the integration of both active and passive data types can improve the monitoring of the CO₂ plume in both time and space. Microseismic monitoring technology has developed rapidly over the last 5-10 years and NORSAR is well positioned to ensure further growth and development of the technology. Microseismic monitoring technology will be important for the upcoming Full-Scale Northern Lights storage project. Results from the CO₂CAP II project will contribute directly to the planning of the monitoring strategy for Northern Lights (Aurora / Smeaheia).

Based on the results from CO₂CAP, a second phase of the collaboration is proposed where the project aims to further analyze the microcephalism at Decatur. This is to develop and quantify a generalized conceptual micro-emissivity model to be used for CO₂ storage. Norsar recently showed that it is possible to invert the source parameters for events on Decatur. By using such characterization and inversion methods quantitatively and linking them to updated and better reservoir parameters, this will increase the understanding of induced earthquakes in general. In CO₂CAPII, the industry at EQUINOR, SHELL and TOTAL will now participate in the project, and the scope will increase from the Illinois Basin / Decatur to also include Quest in Canada. Through the generalization of storage sites, the project will further apply results to offshore monitoring for storage in the North Sea. The project can provide more robust quantitative inversion results (QI), as shown using active and passive data representative of Decatur.

The project will compare the Decatur results with the CO₂ injection at Quest, where microseismicity also occurs in the subsoil. This will make it possible to develop a generalized and conceptual model for microcephalism. It is important to have such a model in place before starting the injection for the upcoming CO₂ storage project in the North Sea. A quantitative understanding of trigger mechanisms will not only help to better utilize the information on CO₂ plum found in microcephalism, but also provide a better and more quantitative estimation of associated risks and provide guidance for developing mitigating strategies.

The proposed project will utilize unique data from the IBDP and Quest projects, and create a generalized conceptual micro-seismic model for CO₂ storage that will apply to the North Sea. In addition, the project will combine active and passive seismic methods to better utilize these wave signatures and to reveal information about the CO₂ range. This will contribute to the quantitative estimation of risk associated with the CO₂ injection, at the same time as it will provide cost-effective solutions for monitoring CO₂ storage.

An important goal for achieving secure storage is to develop methods for reservoir monitoring, which enable cost-effective real-time monitoring of the storage complex. By quantifying micro-seismic events in time and space to distinguish between events in the subsurface and in the reservoir, one will develop an understanding of what happens where. The understanding of micro-seismic events is important for the upcoming Norwegian full-scale project and results from the CO₂CAP-II project will affect how to plan monitoring on the Norwegian shelf, how active and passive instrumentation and seismic surveys can be coordinated to get the best possible picture of how CO₂- the plume moves in the reservoir.