Combining Conformance Treatment with Mobility Control Increases Enhanced Recovery Factor

Abstract

Abstract Mature water floods with high-permeability sands and medium to heavy-gravity crude oil are prime candidates for enhanced oil recovery (EOR) methods. We examined actual field results from the Buffalo Coulee reservoir. The simulation model was history matched on waterflooding and primary. Forecasts were performed with waterflooding and polymer flooding as well as gel treatments. Results indicated that polymer flooding resulted in a 5 to 8% incremental recovery factor over water flooding, while gel treatments resulted in a 2 to 4% incremental when applied separately. However, when gel treatments were performed immediately prior to polymer flooding, simulation showed the incremental recovery was much higher at 10 to 15%. In other words, there was a large synergistic effect of gels with polymers. As seen from long-term production data, interwell tracer analysis, pressure pulse tests, and communication analysis, many waterfloods develop preferred water channels due to preferential flow pathways and/or waterflood-induced fracturing. These channels sometimes cycle large volumes of water from injectors to producers in waterfloods with very high water cuts. These channels also can significantly affect the chemical EOR process. Therefore, it is critically important to understand these preferential paths and flow mechanisms in the reservoir and then, in some cases, take corrective action before tertiary EOR is implemented. Permanently plugging these water channels using crosslinked gel has some significant impacts on improving chemical EOR efficiency and waterflood efficiency. The synergistic effect of the combined treatment significantly improves chemical EOR economics by reducing chemical demand, increasing oil production, decreasing water production, and increasing volumetric sweep.