Direct perturbation of the Peng-Robinson attraction and covolume parameters for reservoir fluid characterization

The direct PnA method is applied to 84 different reservoir fluids, such as gas condensates, volatile oils, and heavy oils. Characterization of each fluid uses the saturation pressure and liquid density data at different pressures at the reservoir temperature. Other phase behavior data available are used to test the predictive capability of the fluid models developed using the PR EOS with the direct PnA method. Results show that the reservoir fluids tested are reliably characterized by the systematic control over phase behavior predictions in the direct PnA method. Unlike prior characterization methods, the direct PnA method does not require estimation of apparent critical parameters of non-identifiable heavy fractions.