Micromechanical mechanism of oil/brine/rock interfacial interactions based on first-principles calculations

Abstract

Understanding the mechanisms of oil/brine/rock interfacial interactions from a nanoscale perspective is essential for enhanced oil recovery (EOR) techniques employed in the exploration of shale oil. Under formation conditions, both metal cations and water molecules could form bridging connections between rock surfaces and the polar oil components, which are referred to as hydrated ion bridges (HIB) and water bridges (WB). In this work, we have comprehensively analyzed the interaction and destruction of various HIB and WB systems. Quasi-static pulling processes were investigated based on first-principles calculations. We found that ions can increase the oil-rock interaction strength, especially for the divalent ions. Various different contributions to interfacial energy were scrutinized from several different approaches. Our results show that water-valeric acid could be the most probable destruction sites at oil/brine/rock interface. Hydrogen bonds and van der Waals interactions were visualized in an intuitive way, which enhance our comprehension on the interaction and destruction of HIB and WB connections. These findings may provide an in-depth insight into oil/brine/rock interfacial interactions and theoretical support for the effective oil extraction.