A NEW MODEL FOR IMMISCIBLE DISPLACEMENT IN POROUS-MEDIA

Immiscible displacement is regarded as the superposition of forward fl ows of both water and oil, due to injection of water into the medium, and of additional forward flow of water coupled with reverse flow of o il, caused by the existence of capillary pressure gradients. The model has been evaluated numerically for the prediction of the evolution of saturation profiles in waterfloods covering a wide range of water inj ection rates. In agreement with experimentation, saturation profiles r anging from a completely pat shape to piston-shape, depending on the i njection rate, have been obtained. Also in agreement with experimentat ion, numerical evaluation of the model for the case of a closed system with an initial step-function saturation profile has predicted a grad ual spreading of the piston front into S-shaped profiles with an incre asing variance. The final profile corresponds to uniform saturation ev erywhere in the medium.