Characterization of asphaltene removal mechanisms from well columns using surface energy

Abstract

The deposition of asphaltene in well columns would compromise flow assurance and possible occurrence of under deposit corrosion. The formed deposit is the net difference between deposition and removal of asphaltene fouling. While there has been a body of research on deposition, the subjects of removal and its dominant mechanisms have received less attention. The present study therefore examines the most important removal mechanisms of shear force, rolling, and rebound under field operating conditions. To achieve this, the removal critical velocity was examined as a function of oil properties of density (870–1000 kg/m3) and viscosity (1.5–3.0 cP), casing diameter (4.5–7 in), and casing substrate (two grades of carbon steel). Experiments were used to determine the preliminary surface energy/tension characteristics of the investigated casing surfaces, crude oil sample, and crude oil-extracted asphaltene particles. The findings revealed that the casing substrate would profoundly influence the removal of asphaltene from the surface whereas the impact of oil properties and casing diameter would be meagre. Furthermore, the larger the asphaltene particles, the greater the possibility for asphaltene removal. For similar thermodynamic, hydrodynamic, and geometrical conditions, the rebound is the major mechanism for removal of asphaltene deposits, according to the predicted critical removal velocities. Finally, to calculate the proportion of precipitated asphaltene particles that would ultimately attach to the surface of the casing, the sticking probability is examined.