Mechanism and visualization of streamline adjustment in enhanced oil recovery: a comparative study between well pattern adjustment and polymer flooding

Abstract

Due to the long-term scouring of steam/water flooding, the water channels restricts the expansion of streamlines in the swept region. The formation of the main streamline, an inevitable and troublesome challenge during steam/water flooding, restrict the spread of the sweep region and the oil extraction in oil reservoirs. To realize the swept main streamlines adjustment (SA), well pattern adjustment (WPA) and polymer flooding (PF) are the mature technologies applied in the development of reservoir. The WAF and PF, as two kinds of oil extracting methods with different principles and operations, is difficult to directly verify the disturbance law to main streamlines in the same model or experimental physical field. Two-dimensional sand-packed model can elucidate the mechanism of WPA and PF for SA based on the direct processing of images and data analysis of production data. Through the oil–water distribution images from displacement experiment, the influence of viscous fingering generated by streamlines development can be obtained and described by the mathematical model to illustrate the relationship between penetration intensity and mobility ratio. In addition, the dynamic production data can reflect the change of flow resistance and water cut during the expansion of swept region. Based on observations of macro and micro perspectives, the experimental results show that the WPA greatly expands the coverage region of the streamlines, while PF makes the streamlines denser in the swept region. By comparing the distribution of streamlines between the two methods, the different shapes of streamlines are deeply influenced by the mobility ratio that determines the viscous fingering and the well pattern type. Finally, the adaptability of different methods for extracting the remaining oil is proposed. The WPA pays attention to improving the macro sweep efficiency outside the swept region. Meanwhile, the PF strategy pays more attention to improving the micro sweep efficiency in the swept region. The analysis of single-factor shows that viscous fingering has an obvious interference effect on the streamline morphology development, which highlights the meaning and importance of using the synergistic effect of WPA and PF to enhance oil recovery.