Heterogeneity effects on pressure and CO₂ saturation during core-scale multiphase flow tests

Carbon capture and storage (CCS) technologies can help manage current emission levels of greenhouse gases while enhancing energy security and diversifying energy economy. For a successful and effective CO₂ geological storage, a comprehensive understanding of the multiphase flow properties of the CO₂/water system in permeable rocks is crucial because they control the engineering design and management of industrial CO₂ storage projects. In this study, we conducted multiphase flow tests at a core-scale to understand the migration behaviors of CO₂ and water in a stratified geologic media (sandstone interbedded with silt). A core-flooding apparatus combined with an X-ray scanning system provided high-resolution experimental dataset of continuous data on the differential pressure (ΔP) across a core plug and CO₂ saturation maps over time. During the multiphase flow tests, we captured dynamic fluctuation in ΔP as CO₂ front advanced by displacing water through different geologic media. The spatio-temporal evolution of CO₂ saturation in each geologic media revealed two increasing stages, implying that the capillary pressure of the downstream geologic media affects the upstream CO₂ saturation. In addition, multiphase transport simulations were conducted to assess the sensitivity of model parameters. Permeability and porosity were respectively sensitive to pressure and CO₂ saturation. Overall, the parameters of the silt layer were more sensitive to the pressure and CO₂ saturation build-up compared to those of the sand layer. Additionally, history matching was conducted to validate the model by sequentially matching ΔP and CO₂ saturation within the stratified system. Finally, we extended the core-scale modeling work further to field-scale and investigated the impact of boundary conditions and heterogeneity on both pressure and CO₂ saturation distribution.