CHARACTERIZATION OF LIBYAN CRUDE OILS AND ITS HEAVY FRACTIONS

Abstract

Characterization of crude oil and its heavy fractions is a necessity to understand and predict their behavior. During production, transportation and processing, various problems such as solids deposition, clogging and coking can occur due to the presence of heavy components in oil. When it comes to the heavier fractions of petroleum, modern analytical methods are not able to fully isolate and characterize the molecules. Crude oils from different origins (Breaga, Sirtica and Bouri) were used in this study. Breaga and Sirtica crude oils are classified as an intermediate crude oils while Bouri crude oil is classified as a heavy one that has shown asphaltene deposition problems. The softening point for the vacuum residues of the three crudes was determined and it was found 42, 40 and 60 for Breaga, Sirtica and Bouri respectively. Compositional studies and structural characterization of the original crude oils and their asphaltenes and maltenes fractions were carried out to study a possible relationship between their properties and asphaltene deposition behavior. Structural characterization is carried out using various techniques including Fourier Transform Infrared Spectroscopy (FT-IR), Softening Point (SP) and Thermogravimetric Analysis (TGA and DTA). Based on the FT-IR results, the asphaltenes have the highest degree of the aromaticity followed by the maltenes and parent crude oils, respectively. Among the asphaltenes materials studied, Bouri asphaltene has the highest aromatic nature as deduced from the absorption at 1600 and 700-900 cm-1. The TGA results show that the weight loss of samples decreased with the increase of the heavy fractions. The asphaltenes sample exhibits a relatively lower weight loss comparing to the rest of samples over the whole temperature interval studied. This agrees with the fact that these samples have the highest heavy fraction, which indicates the presence of less volatile constituents than the other samples. This finding is consistent with the FT-IR analyses.