Research on Foam-Assisted Oxygen-Reduced Air Flooding for Enhancing Oil Recovery in Tight Reservoirs

Abstract

Foam-assisted oxygen-reduced air injection (ORAI) tests were initiated to address critical challenges encountered in the Jiyuan Oilfield within Ordos Basin’s tight reservoirs: pervasive micro-fractures; rapid water breakthrough along dominant fracture planes impairing volumetric sweep efficiency during water flooding; and complex planar water drive patterns yielding low recovery factors under conventional methods. These experiments elucidated the water-blocking mechanism of air foam and defined optimal injection parameters tailored to distinct water drive stages at the field site. By integrating fundamental investigations into bubble displacement mechanics with field implementation, this study established a dynamic identification criterion based on the “recovery factor versus injected pore volume (PV)” curve to differentiate flow regimes between fracture networks and matrix pores. Key interventions included customizing injection modes, injection-production ratios (3.6∼4.5%), and gas-liquid ratios (1.5∼1.8%) for specific water drive stages, supported by stage-contingent technical protocols for rational fluid allocation. Observed well responses in the pilot area fell into three effectiveness categories: reduced water cuts, substantial incremental oil production, and decelerated decline rates. Cumulative incremental oil production reached 9035t. This work provides theoretical guidance for sustaining long-term efficient production while enhancing recovery efficiency in tight oil reservoirs.