The effect of reservoir heterogeneity on the performance of unstable displacements

Abstract

We investigated the effects of reservoir heterogeneity on immiscible, first-contact miscible and multicontact miscible displacements in laboratory scale systems by numerical reservoir simulation. Several two-dimensional heterogeneous permeable media were generated geostatistically and systematically characterized by Dykstra-Parsons coefficient and dimensionless correlation length. The Dykstra-Parsons coefficient and the dimensionless correlation length were varied over wide ranges to cover the conditions normally encountered in petroleum reservoirs and to study their interactions on the performance of unstable displacements. We found that heterogeneity was always detrimental to the recovery performance. The severity of this detrimental effect increased with an increase in the Dykstra-Parsons coefficient and an increase in the correlation length. This detrimental effect of heterogeneity could also be seen in the saturation maps, which showed significantly different fingering patterns for different permeability distributions. These maps also showed fundamental differences in the nature of immiscible, first-contact miscible, and multicontact miscible displacements. First-contact miscible displacements were the most efficient, immiscible displacements were the least efficient, and multicontact miscible displacements were intermediate between the two.