Time-lapse electromagnetic and gravity methods in carbon storage monitoring

Abstract

For geologic carbon storage (GCS), monitoring of the storage reservoir and detection of secondary plumes if they accumulate outside of the reservoir are important to confirm that the injected CO2 stays where intended. Seismic methods are most often applied but are expensive. Due to cost considerations, especially for long-term monitoring, less expensive techniques play a role when designing monitoring networks. In this article, the merits of gravity and electromagnetic (EM) methods as monitoring tools for GCS are presented. Many of the technologies are well established, and several new technologies are on the horizon. EM and gravity techniques are complementary to seismic methods and together provide better subsurface monitoring. Time-lapse multiphysics joint inversion, including seismic, EM, and gravity, could be a game changer for carbon storage monitoring. The trade-off between the sensitivity or resolution to a given plume size and the associated costs will be an important factor in selecting efficient and reliable monitoring arrays at GCS sites. Complex digital models representing geology encountered at storage sites can be used for this purpose and present another cost savings.