Investigation on replacement of blind cave remaining oil by water injection in fractured-vuggy reservoir

Abstract

Due to the complex connectivity of fractured-vuggy reservoirs, there is always a large amount of remaining oil after water flooding development. The blind cave remaining oil, one of the primary remaining oil occurrence forms, is the most difficult to recover. Based on the distribution pattern of these types of remaining oil, the paper designed and manufactured a variety of tube-cave models. Through physical experiment, numerical experiment and theoretical calculation, the ability for water to displace blind cave remaining oil in different conditions, oil-water convective displacement characteristics and the critical parameters for remaining oil development were studied, respectively. The results show that the interfacial tension, fracture width and oil-water gravity difference are the most important parameters to determine whether the remaining oil can be exploited; the wall wettability and oil viscosity mainly affect the oil-water displacement rate due to the loss of non-wetting internal friction. In addition, the interfacial tension should be reduced to 1 mN/m or lower to accelerate the convective flow in the fractures, so that most of the blind cave remaining oil can be developed. This paper provides the influencing factors and exploitation measures of the blind cave remaining oil in fractured-vuggy reservoirs.