Capsule-based chemical delivery for enhanced oil recovery

Chemical flooding is an effective enhanced oil recovery (EOR) method, particularly in oil-wet, low-permeability, and high-viscosity conditions. However, its application is limited by high costs and environmental risks due to chemical losses. As an innovative technology, capsule-based chemical delivery enables targeted chemical release in residual oil-rich areas to significantly reduce the chemical losses. Currently, this technology remains in its early development stages with key challenges, including maintaining capsule stability in high-temperature, high-salinity environments, ensuring long-distance delivery with minimal loss in porous media, and controlling release rates in complex reservoirs. However, advances of capsules in fields like biomedicine and food processing can offer valuable insights. This review refines progress from these areas to address these challenges. It first summarizes strategies for capsule material selection, structural design, and preparation techniques, focusing on their applicability for oil displacement. The impacts of reservoir environments on capsule movement, rupture, adhesion, and blockage are also analyzed, along with approaches to minimize losses and enhance targeting. Triggering mechanisms of capsule release in oilfield environments, transmembrane pathways of chemicals, and description methods for regulating release dynamics are further discussed. Finally, strategies and perspectives for capsule-based chemical EOR are presented. This article provides guidance and broader insights for the applications of capsule in oilfield and other specialized environments.