Probing the interaction mechanism between oil droplets with asphaltenes and solid surfaces using AFM

Area of Science:

• Colloid and Surface Science
• Materials Science
• Petroleum Engineering

Background:

• Wetting phenomena in oil/water/solid systems depend on confined water film stability and oil-solid interactions.
• Understanding these interactions is crucial for applications like oil fouling, corrosion, and separation.

Purpose of the Study:

• To quantify surface forces between model oil droplets and mica surfaces with varying hydrophobicity.
• To investigate the role of interfacial asphaltenes in modifying these interactions in different water environments.

Main Methods:

• Utilized atomic force microscopy (AFM) with a droplet probe technique.
• Studied model oil droplets (toluene, heptol) and mica surfaces in various aqueous solutions.
• Varied mica surface hydrophobicity and water salinity.

Main Results:

• Asphaltene adsorption enhanced electrical double layer (EDL) repulsion at low salinity and steric repulsion at high salinity, stabilizing water films.
• Heptane addition increased asphaltene adsorption, further strengthening repulsive forces.
• On hydrophobized mica, hydrophobic attraction overcame steric hindrance, leading to strong oil droplet attachment.

Conclusions:

• Interfacial asphaltenes modulate surface forces, influencing oil droplet-surface interactions and wetting behavior.
• The findings elucidate nanomechanical mechanisms relevant to oil fouling, corrosion, and separation processes.