Forced and Spontaneous Imbibition of Surfactant Solution into an Oil-Wet Capillary: The Effects of Surfactant Diffusion Ahead of the Advancing Meniscus

Abstract

A previous paper (Hammond, P.; Unsal, E. Langmuir 2009, 25, 12591-12603) reported a simplified model for the flow of a surfactant solution into an oil-wet capillary. Results were computed by neglecting the spreading of surfactant molecules ahead of the moving oil/water meniscus onto the hydrophobic surface. We now present a more thorough version of the theory where such spreading is considered. Both spontaneous and forced imbibitions are studied. As the differential pressure across the capillary increases, a slow increase in the meniscus velocity is observed until the capillary threshold pressure is reached. At this point, the pattern changes and the velocity increases dramatically. The surfactant concentration did not have a significant effect on the speed under differential pressures greater than the capillary threshold. For lower pressures, there is a critical surfactant concentration below which the interface was not able to advance into the capillary even under positive differential pressure.

Molecular Dynamics Simulation of Spontaneous Imbibition in Nanopores and Recovery of Asphaltenic Crude Oils Using Surfactants for EOR Applications

“…3) (as in the case of spontaneous imbibition of a single fluid against vapor). These observations are intuitively correct and agree well with known theoretical predictions [17][18][19]. Deviation from the square-root law at later stages of the rise is related to the decay of the inlet bulk concentration of surfactants, which is considered to be constant in the theoretical studies.…”

A critical review on fundamental mechanisms of spontaneous imbibition and the impact of boundary condition, fluid viscosity and wettability

“…Some research groups reported that surfactant are not only adsorbed onto the solid surface behind the advancing meniscus but also are transported onto the solid surface ahead of the advancing meniscus through the three-phase contact line (Eriksson et al, 2001;Kumar et al, 2003;Kumar et al, 2008). Hammond and Unsal (2010) developed the numerical model on the basis of previous work by considering the mechanism of surfactant transported across the three-phase contact line. Their numerical results showed that advancing velocity of the meniscus is slower than this mechanism is not presented.…”

A Dynamic Pore Network Model for Oil Displacement by Wettability-Altering Surfactant Solution

“…Following (Hammond and Unsal 2010) the total amount of surfactant in a given element, represented as a concentration, is denoted i and so…”

“…In consequence the threshold pressures p i thresh vary over time as the local surfactant concentration changes. Following (Hammond and Unsal 2010) we relate the interfacial tension in element i, σ i , to the local bulk surfactant concentration c i using:…”