Page 49 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

Low-Salinity Water Flooding: from Novel to Mature Technology 31

Figure 2.5 Schematic of permeability-reduction mechanisms in porous rocks related
to fines migration, clay swelling, and changing ionic conditions. Modified after Mohan
et al. (1993).

swelling on various clays, including samples from the Calumbi Formation
(Sergipe-Alagoas Basin, NE Brazil). Their findings supported those of
Mohan et al. (1993) in that CaCl 2 concentrations were shown to be most
effective at inhibiting clay swelling. The CSC to inhibit clay swelling
in the samples studied were: 0.5 M for NaCl, 0.4 M for KCl but only
0.2 M for CaCl 2 .
To study clay detachment and pore blocking, Song and Kovscek
(2016) constructed clay-functionalized, etched-silicon micromodels to
visualize directly the mobilization of clay-mineral grains subjected to
low-salinity conditions. Their results suggested that fines migration that
preferentially blocks the high-water-cut flow channels is a mechanism
that is much more effective in kaolinite-rich systems. They therefore
concluded that LSWF is more likely to result in IOR in kaolinite-rich
systems. On the other hand, in montmorillonite-rich systems, the mobili-
zation of swollen montmorillonite from the pore linings degraded perme-
ability more generally, but crucially did not appear to result directly in
IOR under the LSWF conditions studied. The reduction of permeability