Visualization Experiments on Immiscible Gas and Water Injection by Using 2D-Fractured Glass Micromodels

Abstract

Abstract Two series of flow visualization experiments were carried out to examine the behaviour of immiscible gas injection and water flooding in two-dimensional porous micromodels with fractures at various orientations. One main objective of the study was to test the validity of several contradictory speculative theories that have been proposed in the past in order to explain oil recovery in fractured reservoirs, produced as the result of gas injection or water flooding. All tests were performed under water-wet condition at various injection rates of immiscible gas and water. Our experiments indicated that the average of the maximum oil recovery obtained by immiscible gas injection is about 60%, while it is about 75% by water flooding. The experiments also suggest that, the average oil recovery during gas injection is a strong function of the fracture orientation, whereas the recovery by water flooding is not very sensitive to fracture orientation.Gas injection at rates higher than the free-gravity drainage rate results in displacement fronts that are not stable. The instability is caused by viscous fingering (channelized transport) of the displacing gas through the oil.