Integrative determination of the interactions between SARA fractions of an extra-heavy crude oil during combustion

A good understanding of the interactions between the fractions of Saturates (S), Aromatics (A), Resin (R) and Asphaltenes (A) of crude oils is of great significance for in-situ combustion (ISC). However, due to the vast physiochemical diversity of different crudes, the current data base is not yet sufficient to yield a conclusive combustion map. To add further data to the existing data base and to specifically determine the SARA interactions of an extra-heavy oil, we present combustion results from TG/DSC experiments and model fitting using the crude oil, individual fractions and their binary mixtures (S/A, A/A and R/A). The TG/DSC curves have shown clear evidence for the different combustion pathways of the SARA fractions with temperature. The alterations of peak temperature, heat release, temperature interval, activation energy (Ea), etc., of the binary mixtures revealed the interactions between SARA fractions during nonisothermal combustion. Asphaltenes tended to reacted with the products of saturates and aromatics LTO (low temperature oxidation) reactions, whereas resins did not alter the combustion pathway of asphaltenes presumably due to their similar structures. Saturates and resins can reduce the Ea of asphaltenes HTO (high temperature oxidation) as a result of the boosted coke formation. On the contrary, aromatics inhibited the LTO and HTO combustions, as verified by the increased Ea of these two stages.