Characterization of Libyan Waxy Crude Oils

The prediction of wax formation and the understanding of the physicochemical characteristics of the wax phase are of major importance in flow assurance. The characterization of the oil and wax can provide useful estimates of the parameters and behavior required for operational engineering process developments and/or physical modifications to the processing of crude oils, aiming at the reduction of costs of production and transportation. Five Libyan crude oils and their waxes were characterized using various experimental techniques. Waxes were extracted using the Universal Oil Products (UOP) 46-64 method and purified by column chromatography. Differential scanning calorimetry (DSC) and cross polar microscopy (CPM) techniques were used to study the wax appearance temperature (wAT) for these crude oils. Waxes were characterized using gas chromatography (GC), nuclear magnetic resonance (NMR), and X-ray diffraction (XRD). The carbon number distribution was determined by gas chromatography-flame ionization detector (GC-FID). Extensive information about the structural composition of these waxes was performed using C-13 NMR, and information for the crystalline structure of these waxes was obtained using XRD. This study shows that the five Libyan crude oils studied have wax contents between 8 and 24 wt % with WAT in the range of 22.5-68.17 degrees C. The isolated waxes are shown to be paraffinic (macro-crystalline wax) with an orthorhombic structure.