A comprehensive review of gas‐based enhanced oil recovery ( <scp>gas</scp> ‐ <scp>based EOR</scp> ) techniques: Mechanisms, applications, and future trends

Abstract Gas‐based enhanced oil recovery (EOR) techniques are critical for maximizing hydrocarbon extraction from mature oil reservoirs, extending field productivity beyond primary and secondary recovery methods. This review comprehensively evaluates major gas EOR processes CO 2 flooding, hydrocarbon gas injection, nitrogen (N 2 ) injection, and flue‐gas injection focusing on their mechanisms, applications, economic feasibility, and environmental implications. Unlike prior reviews that address individual gas injection techniques, this paper provides an integrated evaluation of the technical, economic, and environmental dimensions of gas‐based EOR, establishing a unified framework for comparing recovery performance, technology readiness levels, and sustainability potential. Gas injection enhances oil recovery through miscible displacement, viscosity reduction, oil swelling, and reservoir pressure maintenance. CO 2 flooding demonstrates superior recovery efficiency, typically yielding 10%–20% incremental oil recovery beyond secondary recovery, and aligns with carbon capture, utilization, and storage (CCUS) objectives by enabling both enhanced recovery and permanent CO 2 sequestration. Hydrocarbon gas injection (rich and lean gas) achieves 15%–25% additional recovery in light oil reservoirs but faces economic and recycling challenges, whereas N 2 and flue‐gas injections yield 5%–15% and 3%–8% incremental recovery, respectively, providing cost‐effective options for pressure maintenance and late‐stage field rejuvenation. Emerging innovations such as foam‐assisted flooding, nanoparticle‐enhanced injection, solvent‐based EOR, and AI‐driven optimization further improve efficiency and reduce operational risks. Overall, this review highlights gas‐based EOR's potential to enhance oil recovery while reducing net emissions, supporting sustainable hydrocarbon production within evolving low‐carbon energy systems.