Review of EOR-based techniques for enhancing sweep efficiency in carbon geo-storage

Carbon dioxide (CO₂) storage in geological reservoirs faces viscous fingering, gravity override, and poor mobility control due to its low viscosity and resulting inefficient distribution and compromised storage capacity. Therefore, an urgent need arises to thicken the CO₂ and enhance its viscosity for better mobility control and uniform distribution across the reservoir. This study examines the different schemes to enhance sweep efficiency in subsurface storage. In the context of polymer-, surfactant-, and foam-based technologies, the study defines optimization for CO₂ injection and retention. Sweep efficiency is critical in maximizing reservoir usage and minimizing the risk of leakage by ensuring even dispersion of CO₂. Polymers could increase CO₂ viscosity, thereby yielding better mobility control and wider reservoir coverage. Surfactants reduce interfacial tension, enabling CO₂ to invade less permeable areas, while foams act as conformance control agents, changing the flow path of CO₂ away from the high permeability and into the underused areas. The study further includes advanced materials like CO₂-soluble polymers, fluorinated surfactants, and nanoparticle-stabilized foams with superior stability under high-pressure, high-temperature conditions typical of deep reservoirs. Though effective, these approaches are challenged with chemical degradation, economic feasibility and environmental consequences. The study delves into these limitations and suggests integrated approaches involving polymers, and surfactant foams for enhanced sweep efficiency. These findings are a step towards realizing surfactant efficient and sustainable carbon sequestration technologies and contribute to the efforts of the world to mitigate climate change.