At pressures greater than the minimum miscibility pressure (MMP), oil and CO2 are mutually soluble. The dissolved CO2 reduces the viscosity of the oil and causes swelling of the oil phase, hence improving its ability to flow through the reservoir rock. As a mean of reducing emission CO2 is injected into mature reservoir for both sequestration and EOR. In cases where asphaltene is present both processes are affected.
The study here addresses asphaltene precipitation due to pressure, temperature and composition changes during CO2 injection into of asphaltenic oil reservoirs. It is, therefore imperative to identify stability conditions of the asphaltene.
A simple model approach has been developed in this work to determine the asphaltene stability envelope associated with CO2 injection. The model approach is based on Flory-Huggins polymer-solution theory and Hildebrand solubility concept. The model approach is verified by literature data from different crude oil compositions.
In addition a simulation work, by compositional simulator, is done to map the asphaltene deposition within a reservoir, which that confirmed our previous study where it is demonstrated the dependence of asphaltene precipitation on the magnitude of the pressure drop within the production area of the reservoir.