Fig. 1: Pore-invasion mechanisms.
a Temporal evolution of slow fluid-fluid displacement in drainage from experiments in a micromodel patterned with cylindrical posts, where events are colored according to invasion time with tb the breakthrough time. Invasion events are intermittent and b the invading fluid enters throats with lowest entry pressures and occupies pore bodies. Here, gray cylinders represent posts, the invading fluid is marked in blue, and n stands for the pore-scale event number. c In the quasi-static limit, this process is equivalent to invasion percolation on a hexagonal lattice (coordination number Z = 3). Here, red dots and black lines represent network nodes and links, respectively. The dashed lines represent links of a complementary corner-flow network, that is inactive in drainage. d Temporal evolution of slow fluid-fluid displacement in strong imbibition from experiments in the same micromodel as (a). Invasion events are intermittent, and e the invading fluid advances by coating corners between posts and top/bottom plates, leaving pore bodies filled with defending fluid. f In the quasi-static limit, this process is equivalent to invasion percolation on a triangular lattice (Z = 6).
