<p>The FM fault-controlled fractured-vuggy volatile oil reservoir is characterized by strong heterogeneity and insufficient natural energy, which limits the effectiveness of conventional water flooding due to early water breakthrough and significant attic oil retention. To optimize post-waterflood development strategies, this study conducted a series of full-diameter physical simulation experiments using multi-fractured-vuggy cores under reservoir conditions. Experiments with different gas injection media revealed that the stage recovery rates for N₂, hydrocarbon gases, and CO₂ are 78.85%, 64.36%, and 59.96%, with an identical gas injection volume of 0.77 HCPV. Based on these findings, along with the results from phase behavior experiments, N₂ is recommended as the preferred gas injection medium. The cumulative oil recovery after continuous water flooding was about 75%. The subsequent water-alternating-gas (WAG) injection effectively increased oil recovery by approximately 6.6–8.8% relative to waterflooding alone by improving sweep efficiency and mobilizing residual oil in branch fractures. Finally, connectivity-controlled case studies demonstrate that gas injection in upper-connected fractured-vuggy unit provides an additional 11.68% incremental recovery compared with lower-connected unit due to delayed gas breakthrough and expanded sweep volume. Overall, direct continuous gas injection results in earlier gas breakthroughs, premature oil production at the core outlet, reduced gas consumption per ton of oil, and favorable extraction outcomes. Therefore, it is recommended to implement a direct continuous gas injection in the well group following water flooding to enhance crude oil recovery.</p>