Using Dimensionless Numbers to Assess EOR in Heterogeneous Reservoirs

Dimensionless numbers such as mobility ratio and the viscous to gravity ratio provide a convenient way of assessing the flow regime and thus ranking performance when designing secondary and tertiary oil recovery processes. Until recently, however, their application has been limited to homogeneous reservoirs due to a) the lack of a robust heterogeneity index and b) the fact that the viscous to gravity ratio depends upon reservoir permeability and thus heterogeneity. In this paper we present 3D phase diagrams showing how recovery and breakthrough time depend upon mobility ratio, viscous-to-gravity ratio and heterogeneity. We review the literature on the application of dimensionless numbers to identify flow regime in oil recovery processes and select a recently developed heterogeneity index based upon vorticity to characterize heterogeneity. The index has been previously verified using heterogeneous reservoir descriptions taken from SPE10 model 2. We use the phase-diagrams to identify dominant flow regimes and provide criteria based on the dimensionless numbers for identifying those flow regimes when assessing alternative EOR processes.