GEOLOGIC CO2 SEQUESTRATION IN CARBONATE RESERVOIRS - A REVIEW

Over the past three decades, there has been a significant 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 is concerns surrounding the effective containment of CO₂ due to high reactivity, heterogeneity, compartmentalization, mineralogical and other geological complexities. Nonetheless, carbonate reservoirs are often characterized by porosity and permeability that are favorable for CO₂ sequestration, and the frequently occur below and low-permeability cap rock (e.g., shale and/or anhydrite). Moreover, carbonate formations are prevalent in many geologic basins worldwide and in close proximity to anthropogenic CO₂ sources, thus, with proper engineering, thus, will play a significant role in geologic CO₂ sequestration if global emissions reduction targets are to be achieved.

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