The Facies Impact on Dynamic CO2 Storage Capacity and Injectivity of Carbonate Reservoir: A Case Study from Saudi Arabia

Abstract Saline aquifers provide significant storage capacity for CO2 geological sequestration, carbonate reservoirs are increasingly considered as potential subsurface candidate for CO2 storage. However, carbonate reservoirs are more complicated than siliciclastic reservoirs (i.e. sandstone), their complex depositional facies architecture and diagenetic history pose significant challenges for accurate estimation of CO2 storage capacity, injectivity and containment since different reservoir facies exhibit varied rock types, reservoir properties, heterogeneities and diagenetic histories. This study presents an integrated facies-based workflow applied to carbonate reservoir saline aquifer to assess the impact of reservoir facies on CO2 sequestration performance. This methodology combines core description, well logs interpretations, facies classification using principal component analysis (PCA), static modelling, and multi-phase flow simulations. The results indicate that peloidal grainstone and peloidal grain-dominated packstone facies have superior storage capacity and injectivity while maintaining favorable pressure profile, while floatstone and coral-dominated facies exhibit high pressure build-up and lower CO2 injection. This study demonstrates the crucial importance of facies-based modelling for reliable assessment of CO2 storage and risk management in Carbonate reservoirs.