Opportunities and challenges for geologic CO2 sequestration in carbonate reservoirs: A review

Within the last three decades, there has been a remarkable increase in both the adoption and implementation of geologic CO₂ sequestration, a mature and well-established method for reducing greenhouse gas emissions. Numerous research efforts have been geared toward subsurface engineering for effective containment and project scale-up in various types of geologic reservoirs, including sandstones, shales, carbonates, ultramafic, and basalts. However, only a handful of full-scale or pilot projects have been conducted in carbonate reservoirs despite their favorable petrophysical characteristics and wide prevalence across the globe. The principal challenge for CO₂ sequestration in carbonate reservoirs includes concerns surrounding the effective containment of CO₂ due to geologic complexities, such as high reactivity, petrophysical heterogeneity, structural compartmentalization, and mineralogical variability. Nonetheless, carbonate reservoirs are often characterized by porosity and permeability that are favorable for CO₂ sequestration, and they frequently occur below low-permeability cap rock. Moreover, carbonate formations are prevalent in many geologic basins worldwide and in close proximity to anthropogenic CO₂ sources. Thus, with proper engineering, carbonate formations will play a significant role in geologic CO₂ sequestration to achieve the global emissions reduction target.

This paper presents a comprehensive review of carbonate reservoirs in the context of geologic CO₂ sequestration. We explore their unique opportunities and challenges, including their geology, global distribution, and natural CO₂ accumulations. Insights are drawn from a wide range of sources, including experimental studies, numerical and reactive transport modeling, and pilot projects. We highlight the various factors that influence effective CO₂ storage, providing recommendations for successful geologic CO₂ sequestration.