Page 300 - Enhanced Oil Recovery in Shale and Tight Reservoirs

EOR mechanisms of wettability alteration and its comparison with IFT 273

Figure 9.40 Oil and brine contact angles in the liquid-liquid systems (Javaheri et al.,
2017).

oil might be able to imbibe in brine-saturated rock samples as well. Unfor-
tunately, they did not do such imbibition tests. According to Conclusion 2,
the water-wetting angle cannot be used to determine the wettability. In a
separate study, Dehghanpour et al. (2012) observed higher water imbibition
than oil imbibition into the core samples taken from the Horn River basin.
According to Conclusion 3, the water-wetness cannot be determined.
Habibi et al. (2016) reported similar results or observations for Montney
samples. The contact angles on dry, oil-, or water-saturated Montney samples
showed oil-wetness; oil or water volumes imbibing in dry (fresh) samples also
showed oil-wet; but the oil recovery by spontaneous water imbibition was
about 25%e45%, whereas the water recovery by spontaneous oil imbibition
was negligible, indicating water-wetness. We can see that different methods
led to different conclusions about the wettability of the same rocks, without
using Conclusions 2 and 3!
In a rock initially saturated with oil, by considering the effect of oil
viscosity, the water volume by spontaneous imbibition is proportional
q ffiffiffi
to t k s wo cosq wsi
ffiffiffiffiffiffiffiffi , L c is the characteristic length (Ma et al., 1997). The oil vol-
p
4 m o m w L 2
c
ume by spontaneous imbibition into an initially water saturated core should