Experimental study on gas channeling characteristics of nitrogen and foam flooding in 2-D visualized fractured-vuggy model

摘要

Fractured-vuggy carbonate reservoirs are becoming the key to oil reserves, but their complex reservoir structure and connectivity make it difficult to be developed. In this work, a visual physical model representing an underground river reservoir in two-dimensional fractured-vuggy reservoir was designed and fabricated to study gas channeling characteristics of nitrogen and foam flooding. In order to further study the influence of the porous media on gas channeling characteristics of foam and nitrogen gas flooding, the visual physical model was filled with 2 mm transparent glass beads and the effects of glass beads on different types of nitrogen and foam flooding gas channeling were studied. Experimental results showed that the synergistic action of gas and water and the bottom water energy were the important factors affected gas channeling. Furthermore, foam could effectively control gas mobility, delay formation of gas channeling. In terms of enhanced oil recovery, the recovery efficiency of foam flooding was 35% higher than nitrogen flooding in the horizontal model. In addition, the glass beads in fractured-vuggy of underground river reservoirs could change the flow direction of the fluid and cause a certain flow resistance, foam was more easily to occur gas channeling in the longitudinal model filled with glass beads. The oil recovery by foam in the longitudinal model filled with glass beads was lower 12% than that in the longitudinal model. Therefore, determined the factors that influence gas channeling had a practical value for enhancing oil recovery in fractured-vuggy reservoirs.