Abstract
Fluid front tracking is important in two-phase/component fluid flow in porous media with different heterogeneities, especially in the improved recovery of oil. Three different flow patterns of stable, viscous fingering, and capillary fingering exist based on the fluids’ viscosity and capillary number (CA). In addition, fluid front and sweep efficiency are affected by the heterogeneity of the porous medium. In the current study, the heterogeneous porous media are: (1) normal fault zone or cross-bedding with heterogeneity in permeability, and (2) a fracture or discontinuity between two porous media consisting of two homogeneous layers with very low and high permeabilities, in which immiscible water flooding is performed for sweep efficiency and streamlines tracking purposes. By considering the experimental glass micromodel and the simulation results of discontinuity, a crack is the main fluid flow path. After the breakthrough, fluid inclines to penetrate the fine and coarse grains around the crack. Moreover, an increase in flow rate from 1 and 200 (ml/h) in both the experimental and simulation models causes a reduction in the sweep efficiency from 14% to 7.3% and 15.6% to 10% by the moment of breakthrough, respectively. In the fault zone, the sweep efficiency and the streamline of the injected fluid showed a dependency on the interface incident angle, and the layers’ permeability. The presented glass micromodel and Lattice Boltzmann Method were consistent with fluid dynamics, and both of them were suitable for a precise evaluation of sweep efficiency and visualization of preferential pathway of fluid flow through cross-bedding and discontinuity for enhanced oil recovery purposes.
Highlights
Heterogeneity is important in all scales from several kilometres to centimetres, especially for the determination of primary oil saturation and oil distribution of sweep zone by an improved oil recovery process
The results showed that fluid front only depends on the homogeneity of the porous medium, capillary pressure, and fluid saturation (Dawe et al, 1992; Roti and Dawe, 1993)
Fluid front and flow pathway of Lattice Boltzmann Method (LBM) simulation were comparable with the experimental results of the previous study on a glass bead micromodel (Dawe et al, 2011)
Summary
Heterogeneity is important in all scales from several kilometres to centimetres, especially for the determination of primary oil saturation and oil distribution of sweep zone by an improved oil recovery process. Numerical simulations had investigated the effect of gravity, viscosity, capillary pressure, and flow rate within different geological structures, thicknesses, permeability and wettability on fluid flow (Dong et al, 2011; Zhang et al, 2011; Liu et al, 2015). Et al had a sequential study on wettability and permeability heterogeneity in some structures in pore-scale as follows: in 1990, the effects of permeability contrast, lens size, viscosity ratio, and lens heterogeneity on fluid flow were numerically considered and the results were experimentally compared with a glass-bead pack (McKean and Dawe, 1990). A fault/cross-bedding structure with permeability contrasts and in a crack between two layers with different permeabilities or a discontinuity between two different layers These heterogeneous systems geologically exist on both small and large scales. It enables us to visualize and investigate the effects of cross-bedding and discontinuity on fluid pathways and sweep efficiency for enhanced oil recovery purposes
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