Abstract
This study addresses two aspects for mitigating the asphaltene precipitation and deposition problem in Algerian oilfields: experimental study and field solution to the deposition problem. In the experimental study and in order to differentiate cases with substantially impaired production requiring well intervention from those with minimal or no wellbore deposition, we followed a three step strategy mainly; representative single phase sampling, fluid characterization and experimental determination of onset pressure for live oil samples collected from three wells. The near infrared technique, commonly known as solid detection system (SDS), was used to determine asphaltene upper onset pressure (AUOP) and live oil saturation pressure at reservoir temperature combined with compositional and SARA characterization. The obtained results showed that saturates to aromatics ratio, saturates and light ends concentrations in the crude oil can be used to predict the potential for the oil to exhibit asphaltene stability problems. Asphaltene precipitation in Algerian oilfields is aromticity controlled rather than resin controlled. Algerian crude oils can be classified as oils with possible severe asphaltene deposition problems, oils with mild problems and oils with no asphaltene deposition problems. Based on these results, we designed and conducted a series of experiments to attempt to solve the precipitation problem by injecting asphaltene solvent into the well. Results showed that the periodic injection of 5 % solvent, by volume, can ensure solubility of asphaltenes in the entire flow string during production.
