Investigation Of Asphaltenes Onset Pressure (AOP) In Low Asphaltenic Light Oil Samples

Asphaltenes precipitation is common problem in many reservoir field during natural pressure depletion, as well as during gas injection processes for Improved Oil Recovery (IOR) or Enhanced Oil Recovery (EOR). Extensive field and laboratory data has proven that asphaltenes precipitated more easily from light oil rather than from heavy oil, even though the heavier oil might have much higher asphaltenes content.
This study concerns with reservoir simulation investigation of light oil samples on asphaltenes precipitation during pressure depletion and carbon dioxide (CO2) gas injection. Simulation studies have been carried out to understand asphaltenes onset behaviour over a range of pressure at reservoir temperature. A few light oil samples with low asphaltenes content have been chosen to investigate their Asphaltenes Onset Pressure (AOP). Besides, a heavy oil sample with high asphaltenes content has been simulated for comparison purpose. In addition, the onset condition induced by different CO2 concentrations have been investigated over the pressure change as well.
The results of this study have shown that during depressurization, asphaltenes start to precipitate in oil from upper AOP while approaching bubble-point pressure. The precipitated amount increases and reaches maximum around bubble-point pressure. After crossing bubble-point pressure, precipitated asphaltenes reduce and cease precipitation at lower AOP. By injecting higher CO2 mole percentage, bubble-point pressure increases and more asphaltenes precipitate in oil.
In conclusion, these results presented the tendency of asphaltenes precipitation in light oil reservoirs during natural depletion as well as CO2 gas injection. Thus, they can be applied as criteria for designing successful reservoir management strategy to mitigate asphaltenes precipitation problem in light oil reservoir condition.