Page 275 - Enhanced Oil Recovery in Shale and Tight Reservoirs

252 Enhanced Oil Recovery in Shale and Tight Reservoirs

Figure 9.29 Contact angles of surfactant solutions on Wolfcamp siliceous cores from
the same well depth (Alvarez and Schechter, 2017).
in a separate set of contact angle measurements in Fig. 9.29. Similarly, to the
above carbonate cores, the absolute values of zeta potential for the anionic
solutions were lower than those for the nonionic/cationic solutions for
the siliceous cores as shown in Fig. 9.30, not consistent with their contact
angle values. The IFT of the nonionic/cationic solution is higher than
that of the anionic solution, resulting in the much higher final capillary pres-
sures, but the nonionic/cationic solution had lower oil recovery. This indi-
cates that the lower wetting angle is more favorable to oil recovery than the
higher IFT. Generally, anionic surfactants have lower IFT than nonionic or
cationic surfactants.

Figure 9.30 Zeta potentials of different surfactant solutions of a concentration of 2 gpt
on Wolfcamp siliceous cores (Alvarez and Schechter, 2017).