Visualization Experiments on Immiscible Gas and Water Injection by Using2D-Fractured Glass Micromodels

摘要

Two series of flow visualization experiments were carried outrnto examine the behaviour of immiscible gas injection andrnwater flooding in two-dimensional porous micromodels withrnfractures at various orientations. One main objective of thernstudy was to test the validity of several contradictoryrnspeculative theories that have been proposed in the past inrnorder to explain oil recovery in fractured reservoirs, producedrnas the result of gas injection or water flooding. All tests werernperformed under water-wet condition at various injection ratesrnof immiscible gas and water. Our experiments indicated thatrnthe average of the maximum oil recovery obtained byrnimmiscible gas injection is about 60%, while it is about 75%rnby water flooding. The experiments also suggest that, thernaverage oil recovery during gas injection is a strong functionrnof the fracture orientation, whereas the recovery by waterrnflooding is not very sensitive to fracture orientation. Gasrninjection at rates higher than the free-gravity drainage raternresults in displacement fronts that are not stable. Therninstability is caused by viscous fingering (channelizedrntransport) of the displacing gas through the oil.