Figure 2

Pore-filling events and throat size analysis during water injection. (a) Three-dimensional volume rendering of five time steps during fluid invasion into glass beads (semi–transparent), θ ≈ 125°. These images were recorded with a time interval of 5.7 s using the on-board memory of the camera. The aqueous phase was injected at an average front velocity of 3 μm/s. The progressing fluid front is shown in white, blue, yellow, magenta and red. (b,c): Analysis of the large scale experiments shown in Fig. 1 recorded with a time interval of 250 s. Throats and menisci determining the position of the fluid front are identified in a first time step. The fraction of those menisci and throats which still determine the position of the fluid front in a consecutive time step are called ‘arrested throats’ while the fraction of those throats which got filled are termed ‘active throats’. Data are averaged for ten consecutive time steps when the invasion front was already fully developed but not yet exceeded the imaged volume (0.1 \(\lesssim \) PV \(\lesssim \) 0.5). (b) Fraction of ‘arrested throats’ divided by ‘active throats’ as a function of throat size for glass (triangles) and basalt beads (circles) (θ ≈ 75°). The errors in x- and y-direction denote the bin size and the mean value, respectively. (c) Histograms of arrested throats (red), active throats (black), and throats that became filled within the respective time interval and which were not present at the fluid front neither in the first nor in the second time step (blue), normalized by the total number of throats at the fluid front. The throat size distribution of the entire bead pack (gray) is shown at a different scale for better visibility. The corresponding mean values of the distributions are indicated by arrows, and, for the entire bead pack, by the gray dashed line.