Visualization study of polymer enhanced foam (PEF) flooding for recovery of waterflood residual oil: Effect of cross flow

Abstract

Foam injection is an emerging EOR technology that increases oil recovery by reducing gas mobility, especially in heterogeneous reservoirs with permeability variations. Foam can divert flow from high permeability regions to low permeability regions, provided that its stability is high enough to maintain pressure. In this work, a visualization study of foam flow through a two-layer heterogeneous model is presented and the performance of a surfactant-polymer mixture as the foam stabilizer is evaluated. We compared the efficiency of conventional foam (stabilized by a surfactant) and polymer enhanced foam (PEF) flooding (stabilized by a combination of surfactant and PVA polymer) in the glass bead packed models with three permeability ratios (PR) including 2:1, 4:1, and 8:1. Our particular interest was to visualize the effect of the cross-flow mechanism on PEF performance. To achieve the desired permeability ratio, the model was packed with different sizes of glass beads ranging from 150 to 600 μm. The conventional foam and PEF were injected at the tertiary mode for the recovery of waterflood residual oil. Both foam and PEF injection were significantly more efficient than the gas injection; however, the PEF front advancement was more pistonwise; the ultimate oil recovery by PEF flooding was 15–20% more than the conventional foam flooding in all cases of heterogeneous packed models. At higher permeability contrast of the porous medium that the ability of the foam to sweep the porous medium decreases, the PEF still performs better through the cross-flow mechanism due to its higher stability. This makes the PEF injection a more decent candidate for fractured reservoirs where the heterogeneity contrast is high.