Page 46 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

28 David A. Wood and Bin Yuan

Figure 2.3 Mobilization of crude oil during water flooding of a high-water saturation
reservoir with high-salinity and low-salinity injection water. Modified after Tang &
Morrow (1999).

Mixed wettability is required for the adsorption of heavy polar oil
components, as particles coated with formation water would not
allow this (Salathiel, 1973). Some of the mixed-wet fines (i.e., oil
adsorbed onto clay particles) are released (mechanical and chemical
stripping) into the flowing pore fluids from the pore walls during
LSWF. Once in the fluid system, the mixed-wet fines are expected
migrate toward the oil-water interface (Muecke, 1979). A reduction
in salinity was considered by Tang and Morrow (1999) to expand the
electrical double layer in the aqueous phase between particles, which
would ease the stripping of mixed-wet fines and thereby improve
oil recovery.
Visualization models enabled Song and Kovscek (2016) to confirm
that salinity of LSWF had to be below a critical level for clay swelling and
fines migration to occur and significantly impact permeability. They sur-
mized that the redeposition of fines in pore throats and clay bridging due
to swellings is more likely to occur in the high-water-cut flow channels.
Oil sweep of the reservoir would then be improved as the blocked flow
channels would gradually divert injected water toward the higher-oil-cut
flow channels.
Nguyen et al. (2013) developed a simulation to model the concept
that fines migration could be induced by LSWF and exploited to positive
effect to inhibit encroaching water in a depleting gas reservoir. In the