CHARACTERIZATION OF HEAVY OILS .2. DEFINITION OF A SIGNIFICANT CHARACTERIZING PARAMETER TO ENSURE THE RELIABILITY OF PREDICTIVE METHODS FORPVT CALCULATIONS

A new and significant characterizing parameter (q(30)) which is easy t o calculate is defined. This parameter can indicate in advance whether the PVT (pressure-volume-temperature) calculations performed on a cru de oil using a predictive method will be in good agreement with experi mental data. This parameter leads to a new classification of crude oil s. When q(30) is small, the crude oil is considered as ''classical'' a nd all of its PVT properties can be accurately predicted. When q(30) i s large, the crude oil is classified as ''critical-like''; i.e., the p rediction of some PVT properties may lead to significant deviations wh en compared to experimental values. In the latter case, a tuning proce ss is proposed which in all cases improves the agreement between exper imental and calculated data. Moreover, variance analysis theory is app lied to estimate the experimental errors during a differential vaporiz ation.