Experimental Research on Fiber-Gel Composite Flooding for Enhanced Oil Recovery

The development of unconsolidated sandstone reservoirs commonly faces water channeling issues caused by high-permeability channels. Conventional gel plugging systems, characterized by low strength and poor erosion resistance, struggle to effectively suppress channeling and expand sweep volume. As a potential solution, fiber-reinforced gel technology demands systematic investigation into its mechanisms and performance optimization to advance efficient waterflooding development under high-permeability channel conditions. This study systematically analyzed the microstructure, plugging capacity, and sweep-enhancement mechanisms of fiber gels through microstructural experiments (SEM and stereomicroscopy), plugging performance evaluations (sand-packed tube flooding, multi-channel pressure monitoring), and macroscopic visualized flat-plate model experiments. Six distinct fiber types and corresponding fiber-gel systems were comparatively analyzed regarding their injectivity, plugging efficiency, erosion resistance, and oil displacement effectiveness. Experimental findings demonstrate that the fiber-gel composite exhibits superior performance through three synergistic mechanisms: (1) Microstructural analysis reveals fiber-gel networks form bridge structures within pores, where longer fibers create sparser yet more stable architectures. SEM imaging confirms its “steel-concrete-like” composite morphology, contrasting with homogeneous pure gel units. (2) Profile control evaluations show exceptional plugging rates ≥94.39% in high-permeability cores (20D), with residual resistance factor reaching 17.84 and erosion resistance 3–6 times higher than conventional gels, maintaining post-flooding permeability recovery ≤15%. (3) Macroscopic visualization verifies effective flow diversion to low-permeability zones, achieving ultimate oil recovery enhancement of 22.83% - significantly surpassing polymer (6.74%) and pure gel systems (12.63%). These results systematically validate fiber-gel’s technical advantages in conformance control and sweep efficiency improvement. This study elucidates the “bridging-crosslinking” synergistic reinforcement mechanism in fiber-gel composites, validating their dual functionality in high-strength plugging and long-lasting erosion resistance, thereby offering an innovative approach to mitigate water channeling in unconsolidated sandstone reservoirs. The research delivers crucial theoretical and experimental support for optimizing conformance control technologies targeting ultra-high permeability dominant flow channels and developing enhanced oil recovery strategies, underscoring its significant engineering applicability in field implementations.