Chemical additive effect on asphaltenes destabilization and deposition studied using quartz crystal resonator (QCR) sensor: From atmospheric pressure titration to isothermal depressurization of non-diluted crude oil

Abstract

In this study, the destabilization of asphaltenes in a crude oil sample was analyzed under various pressure conditions using a fully immersed Quartz Crystal Resonator (QCR) sensor. Firstly, oil samples with and without a chemical additive were tested at atmospheric pressure through titration with different liquid n-alkanes (C7, C9, and C12) as antisolvents. Then, high-pressure experiments (HP) were conducted on a recombined crude oil + gas system, involving constant mass expansions from 1000 bar to the saturation pressure point at various fixed temperatures. From these high-pressure experiments, the phase diagrams, including the asphaltene pressure envelope (APE), were constructed and compared for the recombined oil with and without the chemical additive in both P vs T and P vs composition diagrams. The results regarding the impact of the chemical additive under HP conditions were compared with those obtained under atmospheric pressure conditions. The comparison shows an strong agreement between the two sets of experiments, confirming that the test conducted to evaluate the effectiveness of asphaltene inhibitors can be extrapolated to high-pressure applications.