Water and aromatics fraction interaction at elevated temperature and their impact on reaction kinetics of in-situ combustion

The combustion tube experiments showed that Oil 1 was able to burn for both conditions (with and without water), while Oil 2 could only sustain combustion with water. To determine the reason for this difference, the burning behavior of the crude oils and their individual SARA fractions with and without water additions was studied through TGA/DSC experiments. At the high heating rate (20 °C/min), heat generation does not vary for both crude oil samples. However, at the low heating rate (5 °C/min), Oil 1 generates a higher amount of energy at high temperature oxidation (HTO) zone. We observed similarities between the decanone (a ketone) burning behaviors with aromatics fractions for Oil 1 which indicates that the aromatics fraction may contain ketone functional groups as LTO products. Upon burning, ketones generate higher energy than any LTO products. Therefore, Oil 1 may have functional groups in its structure more like ketones which promotes its combustion more than Oil 2. While presence of water does not change the burning behavior of Oil 1, we observed that the aromatics fraction of Oil 2 in the presence of water generates components similar to decanol (an alcohol) burning behavior. Note that alcohols generate more heat than aldehydes upon burning which explains the enhancement of Oil 2 burning behavior in the presence of water. However, aldehydes produced less energy than ketones. As a result, the combustion performance of Oil 2 was poorer than Oil 1. These results suggest that the chemical structure of the aromatics fraction is critical for the success of ISC. Water and aromatics fraction interaction at elevated temperature favors ISC reactions.