Study on Hydrothermal Cracking of Heavy Oil under the Coexisting Conditions of Supercritical Water and Non-condensate Gas

Abstract

This study looked at the effects of temperature, water-oil ratio, and the addition of non-condensable gas on the thermal cracking of extra-heavy oil in the lab. The goal was to learn more about the properties and reaction rates of deep extra-heavy oil under supercritical water conditions, which are not well understood. The changes in the composition of the extra-heavy oil were analyzed with and without the presence of non-condensable gas. The reaction kinetics of the thermal cracking of extra-heavy oil were quantitatively characterized and compared between the two conditions of supercritical water alone and supercritical water mixed with non-condensable gas. The results showed that (1) under supercritical water conditions, the extra-heavy oil underwent significant thermal cracking, which led to a significant increase in the amount of light components, the release of CH4, and the formation of a new component, coke, which led to a noticeable decrease in the viscosity of the oil; (2) increasing the water-oil ratio could promote the thermal cracking of extra-heavy oil and led to a significant decrease in oil viscosity, indicating a more complete thermal cracking reaction. Moreover, increasing the water-oil ratio was found to facilitate the flowability of the cracked oil; (3) the addition of non-condensable gas intensified the conversion of coke but inhibited and slowed down the thermal cracking of asphaltene, which is detrimental to the thermal cracking of extra-heavy oil; and (4) the kinetic analysis showed that the addition of non-condensable gas resulted in a decrease in the thermal cracking rate of asphaltene, which is detrimental to the thermal cracking of heavy oil.