A Comparative study of the chemical structure of asphaltenes from Algerian petroleum collected at different stages of extraction and processing

The chemical composition of crude oil, and hence its physicochemical properties, may change during extraction, transportation and treatment. This study characterizes the asphaltene fraction of algerian petroleum collected at three stages of production, namely at the petroleum well, from deposits resulted after petroleum storage, and from the vacuum residuum obtained during the refining process. Mass spectrometry (LDI-TOF), 1H NMR spectroscopy and infrared absorption (FTIR) were used, along with elemental analysis to monitor the composition and average molecular structure of the asphaltene samples. Noticeable differences in chemical structure are found among the three types of samples. The asphaltenes from the storage deposit are particularly differentiated with respect to the other two ones, featuring a higher polarity, a greater heteroatom content, and a lower aromaticity involving a smaller number of substituted aromatic structures. These features must be taken into account when designing strategies to prevent precipitation throughout the production process.