Seismic Modelling: 4D Capabilities for CO 2 Injection

This paper focuses on modelling the seismic response to a theoretical CO 2 injection into the upper reservoir at the Longyearbyen CO 2 Lab site in Svalbard, Norway. The modelling aims to assess the monitoring potential of a carbon capture and storage site. We demonstrate the effect of reservoir porosity and CO 2 concentration on seismic reflection amplitudes using a prestack depth migration simulator. In addition, we look at five different CO 2 plumes of increasing volume and model the seismic response as a proxy to monitoring the evolution of a CO 2 plume. We show that even low porosity reservoirs (2%) will generate a significant seismic response from the injection of CO 2, and that low CO 2 concentrations will also be detected. However, further increases in the CO 2 concentration will not be as simple to monitor, with the CO 2 contact providing the best seismic imaging potential. Furthermore, we demonstrate how illumination angle and hence seismic acquisition design is critical to avoid imaging artefacts.