Characterization of Heavy Oils. 2. Definition of a Significant Characterizing Parameter To Ensure the Reliability of Predictive Methods for PVT Calculations

A new and significant characterizing parameter (q{sub 30}) which is easy to calculate is defined. This parameter can indicate in advance whether the PVT (pressure-volume-temperature) calculations performed on a crude oil using a predictive method will be in good agreement with experimental data. This parameter leads to a new classification of crude oils. When q{sub 30} is small, the crude oil is considered as classical and all of its PVT properties can be accurately predicted. When q{sub 30} is large, the crude oil is classified as critical-like; i.e., the prediction of some PVT properties may lead to significant deviations when compared to experimental values. In the latter case, a tuning process is proposed which in all cases improves the agreement between experimental and calculated data. Moreover, variance analysis theory is applied to estimate the experimental errors during a differential vaporization.