Experiment analysis of remaining oil distribution and potential tapping for fractured-vuggy reservoir

Fractured-vuggy reservoir is characterized by various reservoir spaces, large multi-scale differences, uneven connectivity, and strong spatial heterogeneity, all of which bring great challenges to the understanding of the remaining oil distribution. Therefore, we built a visual physical model based on typical well groups, and intuitively simulated the remaining oil distribution of the fractured-vuggy reservoir through experiments. Then, we discussed the influence of the key parameters, including the injection-production position, injection rate, and bottom water intensity, on waterflooding development and remaining oil distribution. The results show that extending the injection-production distance and avoiding water injecting above the side with a deep dominant pathway is beneficial to enhance oil recovery. In a certain range, the swept area of injected water and displacement efficiency can be increased by appropriately increasing the injection rate. When the development depends on bottom water, the reserves between production wells cannot be effectively used. Based on the experiment results, five types of remaining oil distribution can be summarized: attic-type oil, blocked-type oil, retained-type oil, occluded-type oil, and shielded-type oil. There are multiple types of remaining oil in a fractured-vuggy system, so when tapping the remaining oil, it is necessary to comprehensively analyze the distribution and reserves scale to optimize the tapping scheme and maximize the recovery degree of the reservoir.