Modeling Studies of CO2 Flow and Storage in Saline Karst Formations for Geo-Sequestration

Abstract This study analyzes CO2 storage in saline karst formations, with a particular focus on the impact of vuggy porosity, including randomly distributed vugs, on CO2 storage dynamics. By applying a triple-continuum model in the simulator, the study aims to assess the influence of vugs on storage capacity, CO2 distribution, and injection efficiency, providing critical insights for advancing geosequestration technologies in saline karst formations. A triple-continuum model, representing matrix, fracture, and vuggy continua, was applied in the simulation to capture the complexity of saline karst formations. CO2 injection simulations were conducted under various scenarios, including models with uniformly and randomly distributed vugs. This approach allowed for a detailed comparison of storage dynamics and demonstrated the advantage of the triple-continuum model over the traditional dual-porosity model in accurately describing saline karst formations. Key parameters, such as pressure profiles and the Area of Review (AoR), were monitored to understand CO2 flow and storage behavior, particularly focusing on the effects of vuggy porosity and distribution patterns. The study reveals that vuggy porosity, whether uniformly or randomly distributed, plays a critical role in enhancing CO2 storage capacity within saline karst formations, particularly in waterwet rock formations where vugs offer large storage potential. The triple-continuum model proved superior to the dual-porosity model in describing the intricate flow and storage dynamics in these formations. Modeling results showed that smaller vug porosity expands the Area of Review (AoR), indicating a broader distribution or larger plume of CO2. Randomly distributed vugs create irregular AoR edges, leading to complex and unpredictable flow patterns, which can complicate monitoring and management efforts. These irregularities are further amplified by variations in fracture permeability. Pressure profiles indicated a significant increase during the initial CO2 injection phase, underscoring the need for careful management of injection rates to maintain reservoir integrity. These findings highlight the importance of considering vuggy porosity and utilizing advanced modeling techniques, such as the triple-continuum model, in optimizing CO2 storage strategies and operations in saline karst formations. This study offers a novel contribution by systematically analyzing the role of vugs, both uniformly and randomly distributed, in CO2 storage within saline karst formations. The application of the triple-continuum model provides an improved modeling capability for quantifying these complex systems compared to traditional dualporosity models. The findings deliver practical guidance for engineers to optimize CO2 storage efficiency and manage risks in karst environments, supporting the transition to sustainable energy practices.