A novel electro-deposition based asphaltene removal strategy

Abstract

The deposition of asphaltene on interior pipe surfaces is considered a challenging flow assurance issue. By exploiting the net charge of the asphaltene molecule, it can be effectively removed from the flow stream by means of electro-deposition before transportation to prevent later deposition. To evaluate this concept, electro-deposition of asphaltene from a synthetic oil using varying electric field strength and solvent type were studied. The results demonstrate that the asphaltene molecule possesses a native positive charge, however an induced negative charge can be observed under high current density; depending on the current density, deposition onto the cathode, anode, or both were observed. Both solvent polarity and viscosity affected the removal performance by way of effect on the asphaltene stability and electrophoretic mobility. The interaction of asphaltene and resin resulted in a slight neutralization of charge and strong repression of charge alternation behavior. A series of experiments were conducted to mimic a continuous process by means of repeated electro-deposition cycles. With 8000 V/cm electric field applied, 119 g/m2 asphaltene can be deposited onto electrodes within 10 min using ∼1 kJ energy input. Finally, electro-deposition of actual crude oil was conducted; the electric field strength required to deposit the asphaltene decreased with higher dilution ratio. The speed and high energy efficiency make electro-deposition a promising strategy for asphaltene removal.