Control of asphaltene precipitation and deposition during carbon dioxide flooding enhanced oil recovery

Abstract

Pentane solvent among the two other solvents, hexane and heptane, had a greater ability to extract asphaltene from three crude oils − A, B and C − to precipitate it. The two solvent mixtures (Hexane 75 mL + Pentane 25 mL and 100 mL Pentane + 100 mL Hexane) had the abilities to extract greater yield of asphaltene content from the three different crude oils. Crude oils A and B were analysed to be paraffinic, meanwhile, crude oil C was found to be aromatic. The calculated average of asphaltene content in crude oil A on the ratio of 1:1 solvent-to-solvent mixture were 10.06 g/mL, crude oil B 10.06 g/mL and for crude oil C as 21.33 g/mL. When the solvent-to-solvent mixture ratio was 3:1 the average of the content in crude oil A was 11.8 g/mL, crude oil B 10.13 g/mL and crude oil C 22.65 g/mL. Lastly, the average asphaltene on the single ratio of paraffin solvent in three solvents in crude oil A was 6.86 g/mL, crude oil B 6.06 g/mL and crude oil C 22.73 g/mL. The asphaltene content from the extraction with the solvents was compared with the GC-MS, which further revealed that both analyses resulted in similar conclusions. While CO2 was found to be more influential in its injection in the crude oil, greater asphaltene contents were noted at a temperature of 25oC and lesser at 90oC in all three crude oil types. It can be appreciated that temperature plays a vital role in the process of CO2 flooding of crude oils. The decrease in the CO2-to-oil ratio had an increase in the asphaltene content, keeping the flow rate of the CO2 constant and increasing the amount of crude oil.