(499c) Visualization of Foam Sweep and Oil Displacement in Fractured Porous Media Micromodels

Enhanced oil recovery (EOR) applications are considering foam for gas mobility control to ensure pore-trapped oil can be effectively displaced.  In fractured reservoirs gas tends to channel only through the high-permeable regions, bypassing the low-permeable porous matrix, where most of the residual oil remains.  Because of the unique transport problems presented by the large permeability contrast between fractures and adjacent porous media, we aim to understand the mechanism by which foam transitions from the fracture to the matrix, and how initially-trapped oil can be displaced and ultimately recovered.

                This research presents direct visual observation of foam in fractured porous media micromodels with dimensions on the order of tens of micrometers.  High-speed microscopy videos highlight tunable bubble generation via a flow-focusing microchannel geometry, bubble stability at the foam-oil interface, and dynamic foam behavior at the pore scale (including both fractures and model porous media).  Foam sweep and oil displacement is studied as a function of foam quality, bubble size, surfactant type, and fracture-matrix permeability.  Comparisons are made with pure gas and surfactant-free flooding, showing improved sweep and oil mobilization (up to 98% oil-in-place displaced) for foam systems.

Figure: Foam flooding experiment of a fractured porous media micromodel.  Oil is dyed red (white in threshold); surfactant solution and bubbles are grey, with bubbles having dark black lamellae.  The plot shows fraction of white pixels (representing regions of oil) relative to the initial white pixel count as a function of time.  After 100 seconds,  <2%  of the original oil-in-place remains.