Pore-Scale Investigation of Carbon Dioxide-Enhanced Oil Recovery

Abstract

Carbon dioxide (CO 2 ) enhanced oil recovery is a green and promising way to produce oil and reduce the rapid growth of carbon dioxide released to atmosphere. A pore-scale understanding of CO 2 displacement phenomena is important to enhance oil recovery in porous media. In this work, a direct numerical simulation method is employed to investigate the drainage process of CO 2 in an oil-wet porous medium. The interface between the oil and CO 2 is tracked by the phase field method. The capacity and accuracy of the model are validated using a classic benchmark: the process of a bubble rising. A series of numerical experiments were performed over a large range of values of the gravity number, capillary number, and viscosity ratio to investigate the flooding process of CO 2 in a porous medium. The results show that the pressure in the main CO 2 flow path decreases dramatically after CO 2 breaks through the outlet. Oil begins to reflow into large pores that were previously occupied by CO 2 . This phenomenon has an important impact on the final saturation distribution of CO 2 . Increasing the viscous force is the dominant mechanism for improving oil recovery. Selecting an appropriate depth is the primary consideration for reaching the maximum recovery before CO 2 is injected into the subsurface. Abnormal high-pressure formations represent a good choice for CO 2 sequestration. Gravity fingers improve the sweep area of CO 2 when the viscous force is small. The oil recovery increases with increasing contact angle. It is difficult to reach the final steady state of saturation because of the "snap-off and supplement" dynamic balance in porous media when both the injection velocity and the contact angle are small.

Numerical Approximation of a Phase-Field Surfactant Model with Fluid Flow

“…By taking the inner product of equation (18g) with We , u we obtain       22 We CaCn We , , , 0. 2…”

“…Using our schemes, we investigate the effect of surfactants on droplet deformation and collision under a shear flow, where the increase of surfactant concentration can enhance droplet deformation and inhibit droplet coalescence.2 12]. Unlike sharp interface models [1,[13][14][15][16][17][18][19][20], the phase-field method utilizes an appropriate free energy functional [21][22][23][24][25][26][27][28], which determines the thermodynamics of a system, to resolve the interfacial dynamics, thus it has a firm physical basis for multiphase flows. In the pioneering work of Laradji et al, the phase-field model was first used to study the dynamics of phase separation of in a binary systems containing surfactants [29].…”

Simulation Study of Allied In-Situ Injection and Production for Enhancing Shale Oil Recovery and CO2 Emission Control

“…The shale oil density of 0.79-0.954 g/cm 3 , the gas-oil ratio of 5-350. oil saturation averages 60%. The immovable oil mainly exists in the small pore, while the movable oil mainly exists in the large pore [29]. The salinity of formation water is 10,000-20,000 mg/L and the formation water is a CaCl 2 type.…”

Fully discrete energy stable scheme for a phase-field moving contact line model with variable densities and viscosities

“…Numerous models have been proposed over the years, aiming to understand the hydrodynamic behavior near the MCL, including molecular dynamics (MD) models [5,6], lattice Boltzmann 2 model [7,8], sharp interface models [9][10][11] and the phase-field model [12][13][14] considered in this work. The phase-field model has been widely used in simulations of two immiscible fluid components by coupling the fourth-order Cahn-Hilliard equation with the Navier-Stokes equations via convection and stress terms [3,[15][16][17][18][19][20][21]. In this approach, a phase-field variable is introduced to distinguish the two immiscible phases, and the interface is treated as a thin and continuous layer to remove the singularities [22,23].…”

“…In [38], an energy stable scheme for the phase-field MCL model was constructed based on the invariant energy quadratization (IEQ) approach. The IEQ approach introduces an auxiliary variable to transform the nonlinear potential into a new form, 3 which provides the fundamental support for the linearization treatment. However, this approach requires that the nonlinear potential is bounded from below, and this may not hold for some physical interesting models.…”