Molecular Interactions at the Interface Between Asphaltene and Different Substrates in the Presence of Electrolyte

Nowadays, most of the studies on oil displacement mechanisms are macroscopic, indirect, and empirical, lacking research with respect to the interactions between heavy oil and rock mineral at a molecular level. In this paper, in order to deeply explore the microscopic oil displacement mechanism, molecular interactions at the interface between heavy oil and rock mineral were characterized and analyzed with an in-situ and direct mechanics method, via preparing Atomic Force Microscope (AFM) -N-(1-hexylheptyl)-N'-(12-carboxylicdodecyl)perylene-3,4,9,10-tetracarboxylbisimide (C5Pe) probes and measuring adhesion with different substrates. Effects of substrates (calcium carbonate, mica and silicon dioxide), cations (Ca2+, Na+), salinities (100, 10 mmol/L) and pH (4, 7 and 10) on molecular interactions were investigated. C5Pe, as a model molecule of asphaltene, had the molecular interaction strength with minerals as the following sequence: calcium carbonate > mica > silicon dioxide. Salt effect study results showed that the molecular interactions in CaCl2 solution were stronger than that in NaCl solution at the same salt concentration, which increased with the increase of salinity. Besides, increasing the pH value, the molecular interactions at the interface were weakened, resulting in an easier oil flooding. The conclusions as above manifested that oil flooding was easier in lower salinity with the order of rock minerals: silicon dioxide > mica > calcium carbonate.