Properties for Different Types of Crude Oil: A Comparative Study

Abstract

The objectives of the current study were to study the chemical composition of different types of crude oil in Sudan, the relationship between chemical composition and physical properties of crude oil and to study the emulsion stability of crude oil. Twenty samples collected from four different fields in the South Sudan have been investigated by means of Brookfield viscometer, Anton paar and high-performance liquid chromatography (HPLC). Using HPLC the samples have been separated into four chemical group classes, namely saturates, aromatics, resins, and asphaltenes, the so-called SARA fractions. Using multivariate analysis techniques such as solvent extraction to measure asphaltene content and wax content after precipitation by controlling the temperature, also water cut, emulsion and poor point were measured according to ASTM. The results show that out of the twenty samples studied, nineteen were confirmed waxy samples (Table 1) while one was non-waxy from the pour point and wax content measurements. The SARA analysis carried out on all of the samples. On the other hand, the sample showed a high percentage of saturates ranging from 40 wt% to 66 wt%. Sample 6 which was non-waxy crude oils even had saturates of 40%. Thus, SARA analysis data on its own might not be a tool to distinguish waxy crude oils from non-waxy crude oils. According to the results in chart 4 the API and SARA fractions were correlated in only 45% of the samples studied. On the other hand, in 55% of the studied samples the correlation between SARA and API was not clear. There is an increase of the emulsion stability as the viscosity increases. However, viscosity also correlates well with the SARA data of the crude oils, Pour point correlates fairly well to resins, aromatic and saturates,