Comprehensive review of hybrid chemical enhanced oil recovery methods: synergistic mechanisms, applications, and insights into chemical-based water alternating gas techniques

With the global depletion of oil reserves, the need for efficient Enhanced Oil Recovery (EOR) practices has become increasingly critical. Among these, chemical EOR stands out as a promising approach, though individual chemical methods face inherent limitations. To overcome these challenges, hybrid EOR methods combining different chemicals have been developed, leveraging synergistic mechanisms to enhance robustness, prolong the productive life of oil fields, and significantly improve recovery factors. This paper reviews laboratory-scale research, pilot projects, and field operations of various hybrid methods, including Water Alternating Gas, Polymer Alternating Gas, Surfactant Alternating Gas, Alkaline-Surfactant-Polymer, Alkaline-Surfactant-Polymer Alternating Gas, Alkaline-Surfactant Alternating Gas, Alkaline-Surfactant, Alkaline-Polymer, and Surfactant-Polymer methods. Mechanisms of these techniques are analyzed, along with screening criteria and radar graphs for each method. Based on the reviewed studies, Surfactant-Polymer emerges as the most promising technique, offering high recovery factors despite operational challenges. By providing a comprehensive comparative analysis and practical insights, this study aims to guide future research and drive the development of innovative EOR strategies to address evolving energy demands.