Strategic investigation of EOR by surfactant-assisted CO₂-WAG: A pathway toward low-carbon oil production

Abstract

The target reservoir contains a high proportion of heavy components in the crude oil, resulting in a high minimum miscibility pressure (MMP) between CO₂ and the crude. Additionally, conventional CO₂-WAG flooding is prone to gas channeling, leading to premature gas breakthrough at production wells. This study investigates the synergistic potential of surfactant-assisted CO₂ water-alternating-gas (SA-CO₂-WAG) technology to enhance oil recovery while concurrently addressing low-carbon oil production. Through systematic core flooding experiments under actual reservoir conditions (93°C, 22 MPa), the research evaluates the impact of surfactant concentration (0.1–0.5 wt%) and injection rate (0.1–0.4 mL/min) on recovery efficiency. Results demonstrate that SA-CO₂-WAG significantly outperforms conventional CO₂-WAG, achieving an incremental recovery of 24 % compared to 16.2 % for CO₂-WAG, attributed to interfacial tension reduction, wettability alteration, and foam stabilization. Optimal performance was observed at 0.3 wt% surfactant concentration and 0.2 mL/min injection rate, beyond which diminishing returns occurred due to micellization, pore-throat blockage, and adsorption saturation. The study further explores policy frameworks to accelerate SA-CO₂-WAG deployment, emphasizing standardized parameter guidelines, carbon credit incentives, and cross-sectoral infrastructure integration. These findings highlight SA-CO₂-WAG as a dual-purpose solution for low-carbon oil production and carbon sequestration, aligning with global energy transition goals.