CO2 Displacements of Reservoir Oils From Long Berea Cores: Laboratory and Simulation Results

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Abstract
Summary: CO2 displacements of three different reservoir oils from long Berea cores were conducted over a wide range of reservoir conditions with the pressure always above the slim-tube minimum miscibility pressure (MMP). The detailed performance of these displacements is simulated with a fully compositional simulator and the Redlich-Kwong (RK) equation of state (EOS). Oil recovery, GOR, and effluent profiles are compared with experimental results. The EOS is observed to be capable of predicting the phase-behavior transitions that occur in situ when miscibility is generated by multiple contacts. The good comparison between experimental results and the simulation has led to specification of a minimum data set for which an EOS should be able to predict before a priori simulations of displacement experiments can be made. The simulation assumed a stable one-dimensional (ID) displacement and that phase-behavior effects play the primary role in the displacement, but the number of gridblocks had to be adjusted in a rough correlation with the CO2/oil-viscosity ratio. Experimentally, final oil saturation and CO2 breakthrough time also correlate with the viscosity ratio. This suggests that viscous instabilities play a role in the experimental displacement, but in this geometry and under these displacement conditions, they can be simulated as numerical dispersion.