Special Core Analysis Model – SCAL Model for CCS: Insights From the First Commercial CO2 Project on the Norwegian Continental Shelf, Northern Lights

Relative permeability and capillary pressure are multiphase flow properties that determine reservoir fluid dynamics for fields in production and for new field developments. These key parameters are characterized by a special core analysis (SCAL) model. For carbon capture and storage projects (CCS), multiphase flow properties are equally important. Interpretation of SCAL experiments and implementation of the SCAL model for full-field simulations will be shared to highlight the impact of the SCAL model uncertainty on the estimation of the carbon dioxide (CO2) storage resource assessment and plume migration for the Northern Lights project—the world’s first open-source CO2 transport and storage infrastructure. In the case of CO2 storage in a saline aquifer like in the Northern Lights project, the flow process is inverse to the hydrocarbon production as water saturation decreases from unity saturation toward a residual water saturation when the CO2 plume propagates through the formation. Therefore, there is a need to provide the SCAL model for the process and system applicable for CCS , i.e., primary drainage type when the CO2 plume develops and residual trapped CO2 when the aquifer later imbibes into the stored CO2. Nitrogen (N2) has frequently been used by the industry in ambient conditions as a proper analog fluid to CO2 to achieve fluid flow properties without the need for SCAL experiments in resource-demanding reservoir conditions with supercritical CO2. For the SCAL model presented here, we have also included experiments with supercritical CO2 at reservoir conditions. Several multiphase flow experiments have been performed, and comprehensive interpretation work has been performed using the core flow simulations tool Sendra®. The experiments cover steady state for relative permeability, multispeed centrifuge, and porous plate for capillary pressure and residual water saturation, as well as unsteady-state trapped gas experiments to provide data for determination of residual capillary-trapped CO2.