CO2‐oil saturation pressure and onset asphaltene precipitation

Abstract

Partial miscible flooding using CO2 injection has been shown to be a promising method for enhanced oil recovery, but this injection could result in asphaltene precipitation, which clogs the reservoir and production equipment. Therefore, an important parameter to be monitored is the onset of asphaltene precipitation. The efficient displacement of oil by CO2 depends on a variety of factors, including phase behaviour of CO2/crude‐oil mixtures that requires an accurate description of the CO2‐oil mixture bubble pressure. Observing bubble pressure behaviour, it is possible to exactly determine the CO2 molar fraction for onset asphaltene precipitation, which is expected to occur when the selected injection pressure is equal to the bubble pressure at the same CO2 molar fraction. However, assessment of oil characterization relating CO2‐oil mixture bubble pressure and onset asphaltene precipitation has not been found in the literature and should be properly addressed. In this work, we employed the Soave‐Redlich‐Kwong equation of state and used CO2‐oil mixture bubble pressure experimental data from literature to show that the accuracy of onset asphaltene precipitation is quite affected by the binary interaction parameter between methane and C7+ fractions, and the density of this heavy fraction.