Use of real crude oil fractions to describe the high pressure phase behavior of crude oil in carbon dioxide

Abstract

The knowledge about crude oil phase behavior at high-pressures is a challenge for scientists due to inherent complexity to this systems. Some works employ model systems attempting to predict crude oil behavior, but the results are normally poor. In this sense, the use of real crude oil fractions can be an alternative to improve the accuracy of the models used in these simulations. In this work, a light oil sample has been fractionated to generate four representative fractions. An approach to estimate the critical properties of these distilled fractions using only density and vapor pressure experimental data is presented. In sequence, phase behavior of the pseudo binary (carbon dioxide (CO2)+real crude oil fractions), multicomponent (mixture of fractions+CO2) and original crude oil+CO2 systems were determined using static synthetic method and static synthetic+NIR, with CO2 molar fraction range of 0.367-0.986, temperature range of 20⿿80°C and pressure up to 300bar. Binary interaction parameters (BIP) were estimated for each pair (CO2+distilled fraction) and employed to describe the phase behavior of a CO2+crude oil systems with Peng-Robinson equation of state (PR-EOS) and quadratic mixing rule. The results suggest that the use of real fractions can be a safer strategy for predicting the phase behavior of petroleum in carbon dioxide. Besides, NIR spectroscopy showed to be a good alternative to study phase behavior of dark/opaque systems.