Page 334 - Enhanced Oil Recovery in Shale and Tight Reservoirs

Spontaneous imbibition 307

surfactant with the alkali additive behaved best in oil recovery. There was no
alkaline precipitation observed, as the interaction between the soap and the
nonionic surfactant is mainly a hydrophobic interaction of the hydrocarbon
tails, not like the interaction between the opposite head groups of the soap
and the cationic surfactant.
However, Nguyen et al. (2014) observed that a cationic surfactant (0.2%
concentration, no alkali additive) produced the highest oil recovery (27%
after 600 h of imbibition) from an Eagle Ford core aged with Bakken oil.
The cationic surfactant altered the oil-wetness to water-wetness. The Eagle
Ford core is carbonate dominated (47%). This result is consistent with that
from Alvarez et al. (2018) that a cation works better with a carbonate
core, as discussed in the last chapter of this book.