Fractured-vuggy carbonate reservoir has the characteristics of special storage space, complex connection mode and fluid flow law, which lead to big differences in characteristics of remaining oil after waterflooding. By visual physical simulation experiments, two different models have been established and the process of waterflooding has been simulated in this paper. The results show that the types of remaining oil, including remaining oil trapped in the closed fractures and caves, by-pass oil, attic oil and oil film have been determined. Remaining oil is trapped in the closed caves due to bad connectivity with other fractures and caves. Because the minimum resistance is the fluid flow direction, the by-pass oils are easy to form under the link between the fractures and caves. The attic oils are trapped in the top of caves where the flooded water can not arrive in. On the wall of fractures and caves, the oil films form, which are affected by wettability, oil viscosity and temperature.
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