Masoud Riazi - Enhanced Oil Recovery (EOR) Research Centre, School of Chemical and Petroleum Engineering, Shiraz University, Shiraz, Iran
Yousef Kazemzadeh - Department of Petroleum Engineering, School of Chemical and Petroleum Engineering, Shiraz University, Shiraz, Iran
Rafat Parsaei - Department of Petroleum Engineering, School of Chemical and Petroleum Engineering, Shiraz University, Shiraz, Iran

Asphaltene precipitation in oil reservoirs has been involved with numerous problems. Therefore, it is imperative to understand the precipitation mechanisms in detail. There are several ways to detect asphaltene precipitation, i.e. interfacial tension method. In this study, for more accurate evaluation of asphaltene precipitation by using IFT versus pressure plots, synthetic oil solutions made up of toluene and normal paraffins are used. Solutions with different compositions of toluene and normal paraffins with and without asphaltene (extracted from crude oil) are prepared. Then, the IFT of the solutions in the proximity of CO۲ at different pressure conditions is measured. By plotting the IFT data versus pressure, the onset of asphaltene precipitation and the impact of different parameters on this phenomenon are investigated. Experimental results show that the presence of asphaltene in synthetic solutions changes the behavior of IFT data with pressure. For a solution containing asphaltene, the IFT of the solution in presence of CO۲ decreases linearly with two different slopes. The results confirm that the presence of n-paraffin intensifies asphaltene precipitation. The experimental results also show that the higher the mass fraction of asphaltene is, the larger would be the intensity of the asphaltene precipitation for the attempted mass fractions.

Asphaltene precipitation, Interfacial tension, Surface Coverage, Carbon dioxide, Normal Paraffin