Impact of Geological Heterogeneity at Facies and Facies-Association Scales on CO2 Storage in Shallow Marine Reservoirs

Abstract

Assessment of CO2 storage capacity in shallow marine reservoirs must be underpinned by understanding of the impact of geological heterogeneity (Zhang et al., 2025). Heterogeneity is present at multiple scales from laminae (cm’s) to facies (m’s), to facies associations (10’s m), to parasequences (100’s m), to parasequence set (km’s) scale. Using a multiscale representative elementary volume (REV) approach, we investigate how heterogeneity at the facies and facies association scales impact properties such as effective permeability and effective relative permeability that are key inputs for simulating storage at reservoir scale. Facies-scale (m’s) heterogeneity clearly impacts effective permeability values and effective relative permeability curves, and their anisotropy. Models that capture the heterogeneity architecture of facies in 3D form a robust basis to link plug-scale (cm’s) measurements to larger scales, providing values that are potentially directly usable in flow simulation assessing CO2 flow dynamics and trapping for CCS. Upscaled relative permeability curves are anisotropic and can vary outside the bounds of the input curves as a direct result of 3D heterogeneity. This finding demonstrates that sedimentological heterogeneity affects CO2 flow and storage and illustrates how core-plug-scale measurements can be used to make predictions that incorporate the effects of facies-scale heterogeneity at larger scales.