MATRIX BLOCKS IMBIBITION IN FRACTURED RESERVOIRS.

A numerical model to simulate the imbibition process in single matrix blocks has been developed in this paper. The results, which can be used to evaluate water-flooding in naturally fractured reservoirs, show that blocks entirely surrounded by water produce less oil than blocks partially invaded by water. This study shows that for a given dimensionless time, t//D, or capillary forces/viscous forces ratio, the taller are the matrix blocks, the lower is the recovery. When t//D is larger than 10, the difference in oil recovery between tall and short matrix blocks becomes substantial (more than double in some cases). In general, for a given t//D the recovery decreases when the dimensionless number pi (the ratio between the capillary and the gravity forces) decreases.