Effect of Viscosity Action and Capillarity on Pore-Scale Oil–Water Flowing Behaviors in a Low-Permeability Sandstone Waterflood

Abstract

Water flooding technology is an important measure to enhance oil recovery in oilfields. Understanding the pore-scale flow mechanism in the water flooding process is of great significance for the optimization of water flooding development schemes. Viscous action and capillarity are crucial factors in the determination of the oil recovery rate of water flooding. In this paper, a direct numerical simulation (DNS) method based on a Navier–Stokes equation and a volume of fluid (VOF) method is employed to investigate the dynamic behavior of the oil–water flow in the pore structure of a low-permeability sandstone reservoir in depth, and the influencing mechanism of viscous action and capillarity on the oil–water flow is explored. The results show that the inhomogeneity variation of viscous action resulted from the viscosity difference of oil and water, and the complex pore-scale oil–water two-phase flow dynamic behaviors exhibited by capillarity play a decisive role in determining the spatial sweep region and the final oil recovery rate. The larger the viscosity ratio is, the stronger the dynamic inhomogeneity will be as the displacement process proceeds, and the greater the difference in distribution of the volumetric flow rate in different channels, which will lead to the formation of a growing viscous fingering phenomenon, thus lowering the oil recovery rate. Under the same viscosity ratio, the absolute viscosity of the oil and water will also have an essential impact on the oil recovery rate by adjusting the relative importance between viscous action and capillarity. Capillarity is the direct cause of the rapid change of the flow velocity, the flow path diversion, and the formation of residual oil in the pore space. Furthermore, influenced by the wettability of the channel and the pore structure’s characteristics, the pore-scale behaviors of capillary force—including the capillary barrier induced by the abrupt change of pore channel positions, the inhibiting effect of capillary imbibition on the flow of parallel channels, and the blockage effect induced by the newly formed oil–water interface—play a vital role in determining the pore-scale oil–water flow dynamics, and influence the final oil recovery rate of the water flooding.

Review on Oil Displacement Technologies of Enhanced Oil Recovery: State-of-the-Art and Outlook

“…The water driving force at the bottom and the oil–water IFT affect the oil–water flow in the dynamic oil displacement process. Ning et al investigated the effect of capillary action on fluid flow in water flooding from a microscopic perspective. The results indicate that the obstacles in the main displacement capillary lead to the lateral flow of the fluid, and the obstacles in the lateral displacement capillary block the further flow of the fluid.…”

Improving the Efficiency of Oil Recovery in Research and Development

“…In work [31], the authors rightly state that flooding technology is an important measure for increasing the recovery of crude oil in oil fields. In this paper, the authors used the direct numerical simulation (DNS) method, which is based on the Navier-Stokes equation and the fluid volume (VOF) method, to investigate the dynamic behavior of oil-water flow in a low-permeability pore structure [32,33].…”

Liquid-like nanofluid mediated modification of solar-assisted sponges for highly efficient cleanup and recycling of viscous crude oil spills

“…The long hydrophobic chains of the SiO 2 nfs rapidly capture crude oil molecules on the water surface and transport them to the interior of the sponge. Subsequently, the hydrophilic chain segment of the SiO 2 nfs is utilized to emulsify the viscous crude oil into a lower viscosity oil-in-water type emulsion, 33 which promotes the transport and stripping of crude oil in the sponge voids and sustains a high transport rate. Benefiting from the synergistic advantages of the SiO 2 nfs and the photo-thermal properties of the dopamine layer, 34 compared to a commercial polyurethane sponge, the modified sponge exhibits a 10% increase in absorption capacity and a three order of magnitude increase in viscous crude oil absorption rate, and its crude oil recovery rate remains stable at over 90% after 10 cycles.…”