Deposition of asphaltene on pipeline surface: insight from molecular dynamics simulations

Adsorption and deposition of asphaltenes on oil pipeline walls poses significant challenges in the oil and gas industry but the underlying mechanisms are still poorly understood. In the present study, molecular dynamics simulations were carried out to investigate the adsorption and deposition of asphaltene on oil pipeline surfaces. The small-aromatic core long-side chains APH molecule and the large-aromatic core short-side chains B1-6 molecule were selected as the model asphaltene molecules. The results suggested that both APH and B1-6 adsorbed parallelly on the pipeline surface and the hydroxyl-pi interactions played an important role in asphaltene adsorption. Adsorption of B1-6 was significantly more stable than APH and the free energy results indicated that the adsorbed small-core asphaltenes can be replaced by large-core asphaltenes on the pipeline surface. Adsorption of additional asphaltenes on the pre-adsorbed asphaltene layers was thermodynamically favored, leading to the deposition of asphaltenes. The pi-pi attractions between the aromatic cores of asphaltenes were responsible for asphaltene depositions on pipeline walls. The findings obtained in the present study provide valuable insights into the deposition of asphaltenes and form a molecular-level basis for developing efficient mitigation strategies.