Petrography and pore-scale assessment of CO2 mineral trapping potential of sedimentary strata beneath the lower mainland British Columbia, Canada

• Diagenesis-informed framework links mineralogy to pore accessibility. • Fe-chlorite, Ca-plagioclase, and Ca-zeolite show highest trapping potential. • Huntingdon Fm highest mineral trapping capacity but heterogeneous; Boundary Bay Fm best target due to porosity and regional extent. • Significant variability in detrital and diagenetic mineralogy across formations. • Pore-lining clays and fines migration pose risks to injectivity and permeability. Sedimentary strata within the Georgia Basin and beneath the Lower Mainland of British Columbia have been identified as having potential for carbon storage. The sedimentary fill of the Georgia Basin comprises three main packages, including the Nanaimo Group, Huntingdon Formation, and Boundary Bay Formation, and sandstones within these units are evaluated for their CO₂ mineral trapping potential. A total of 88 samples representing the full range of lithofacies, were analyzed using automated mineralogical analysis (SEM-EDS) to quantify bulk mineral proportions and characterize petrographic textures. From this dataset, seven reservoir-quality samples were further selected for quantitative trapping capacity estimates and pore-mineral association analysis. Based on their reactivity with CO 2 , diagenetic features, and operational risks (e.g., permeability reduction or fines migration), these samples were group in four categories: smectite pore-lining, calcite cemented, kaolinite pore-filling, and zeolite pore-filling. Of these, kaolinite pore-filling and zeolite pore-filling are the most favorable for mineral trapping while smectite pore-lining is the least favorable. The Boundary Bay Formation preserves the best porosity (10 %–20 %) comprising interconnected intergranular pores and secondary pores from plagioclase dissolution. The estimated upper-bound for mineral trapping capacities in the Boundary Bay Formation ranges of 38–99 kg CO₂/m³. The Huntingdon Formation displays heterogeneous porosity (5 %–15 %) and contains pore-accessible zeolite and detrital chlorite; one quantified sample indicates an upper-bound capacity of ∼103 kg CO₂/m³, reflecting the potential reactivity of Ca-zeolite and Fe-chlorite. In contrast, the Nanaimo Group records advanced burial diagenesis dominated by calcite and chlorite cementation, which occludes primary porosity and restricted fluid connectivity, thus limiting trapping potential. Our findings demonstrate that reactive mineral abundance alone is insufficient for assessing storage potential; diagenetic context and pore-scale accessibility are critical controls. The mineralogical and textural constraints presented here, together with the diagenesis-informed approach, provide essential input for future geochemical modelling of CO₂–water–rock interactions and help reduce uncertainty in evaluating CO₂ storage potential in sedimentary reservoirs.