Calculation of wax appearance temperature directly from hydrocarbon compositions of crude oil

Abstract

The purpose of this research is to develop a correlation in order to calculate the wax appearance temperature directly from hydrocarbon compositions of crude oil. Different methods have been used to measure wax appearance temperature including experimental instruments and thermodynamic models. A lot of empirical correlations have been used to calculate the physical properties of crude oil. However, there are no correlations for calculating the wax appearance temperature of the crude oils based on hydrocarbon compositions of crude oil. Calculation of the wax appearance temperature has become crucial in the study of wax crystallisation to prevent any congealing of the crude oil in production facilities and transportation pipelines. In this study, new correlations based on the hydrocarbon compositions of crude oil are developed to calculate the wax appearance temperature. The DataFit® scientific software’s multiple nonlinear regression analysis tools are used as a platform to develop a novel correlation to calculate the wax appearance temperature. Two correlations are developed. The accuracy and reliability of these correlations were verified experimentally and thermodynamically by different thermodynamic models. The R2 and AAD% for these correlations (Eqs. 4 and 5) are 0.973,0.999, 0.0170 and 0.00028 respectively. It can be concluded that the correlation equations are acting better than the thermodynamic wax model in predicting the wax appearance temperature of the crude oils. However, this correlation does not have the capability of thermodynamic wax models in prediction of the phase equilibriums at any temperatures and pressures and are subject to availability of the hydrocarbon composition range as indicated.