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R. Sandeep et al.
with a combination of nanoparticles compared to using silica-based nanoparticles
(Cheraghian and Hendraningrat 2016).
Few of the researchers have also studied the blends of nanoparticles and surfactants. Le et al. had studied such combination using SiO 2 NPs for EOR in high
temperature reservoirs (Le et al. 2011). Resasco et al. had found more interesting
results (Resasco et al. 2015). Their studies showed that when a mixture of nanoparticles and anionic surfactants is used for EOR, the reduction in IFT is 70% more
compared to the sole use of surfactant. The increased adsorption of nanoparticles
modifies the interfaces of oil and water, thereby reducing the IFT (Munshi et al.
2008; Ravera et al. 2006).
3.1.3 Wettability Alteration
The term wettability reflects the tendency of a liquid to adhere to a solid surface
while competing with another immiscible liquid (Le Van and Chon 2016). In the
context of oil fields, wettability alteration refers to the change of the reservoir rock
surface toward water wet (Mohammed and Babadagli 2015). It is an important factor
that affects the oil recovery process by influencing capillary pressure, relative permeability and fluid saturation (Sun et al. 2017). In general, the efficiency of crude
oil recovery decreases when the surface of reservoir rock becomes more oil wet.
Several different thermal and chemical EOR methods have been proposed that alter
the wettability of rocks toward water wetness, although this ability depends upon the
characteristics of rock mineralogy and that of brine and oil composition. Besides,
because of reservoir heterogeneity, the potential of wettability alteration depends
upon the crude oil interaction of the crude oil with the rock and brine that differs
from reservoir to reservoir (Mohammed and Babadagli 2015).
Wettability alteration occurs by changing oil, brine and rock characteristics due
to two different mechanisms: coating and cleaning (Giraldo et al. 2013). Coating
results in the covering of the oil wet surfaces by a water wet layer such as that of
surface active agents and NPs. For example, certain NPs are hydrophilic in nature,
such as zirconium nanoparticles (Karimi et al. 2012). Cleaning occurs due to surface
active agents such as cationic surfactants that wipe out the oil wet layers rendering
the surface more water wet (Standnes and Austad 2000). A combined effect was also
noticed when a mixture of anionic surfactant and alumina NPs was used (Giraldo
et al. 2013).
A number of wettability alteration measurement techniques are used, such as
contact angle measurement (CAG), spontaneous imbibition (SI), zeta potential measurement (ZPM) and surface imaging tests (atomic force microscopy, SEM, NMR).
CAG is the measurement of the point at which oil and water interface meets at rock
surface. It is used to monitor the altering wettability of the surface by measuring the
shift of the affinity of rock surface toward one fluid than another in an advancing
manner (Morrow 1990). Magzhi et al. had used CAG approach to monitor change
in wettability of glass surfaces coated with SiO 2 nanofluid and oil with different
R. Sandeep et al.
with a combination of nanoparticles compared to using silica-based nanoparticles
(Cheraghian and Hendraningrat 2016).
Few of the researchers have also studied the blends of nanoparticles and surfactants. Le et al. had studied such combination using SiO 2 NPs for EOR in high
temperature reservoirs (Le et al. 2011). Resasco et al. had found more interesting
results (Resasco et al. 2015). Their studies showed that when a mixture of nanoparticles and anionic surfactants is used for EOR, the reduction in IFT is 70% more
compared to the sole use of surfactant. The increased adsorption of nanoparticles
modifies the interfaces of oil and water, thereby reducing the IFT (Munshi et al.
2008; Ravera et al. 2006).
3.1.3 Wettability Alteration
The term wettability reflects the tendency of a liquid to adhere to a solid surface
while competing with another immiscible liquid (Le Van and Chon 2016). In the
context of oil fields, wettability alteration refers to the change of the reservoir rock
surface toward water wet (Mohammed and Babadagli 2015). It is an important factor
that affects the oil recovery process by influencing capillary pressure, relative permeability and fluid saturation (Sun et al. 2017). In general, the efficiency of crude
oil recovery decreases when the surface of reservoir rock becomes more oil wet.
Several different thermal and chemical EOR methods have been proposed that alter
the wettability of rocks toward water wetness, although this ability depends upon the
characteristics of rock mineralogy and that of brine and oil composition. Besides,
because of reservoir heterogeneity, the potential of wettability alteration depends
upon the crude oil interaction of the crude oil with the rock and brine that differs
from reservoir to reservoir (Mohammed and Babadagli 2015).
Wettability alteration occurs by changing oil, brine and rock characteristics due
to two different mechanisms: coating and cleaning (Giraldo et al. 2013). Coating
results in the covering of the oil wet surfaces by a water wet layer such as that of
surface active agents and NPs. For example, certain NPs are hydrophilic in nature,
such as zirconium nanoparticles (Karimi et al. 2012). Cleaning occurs due to surface
active agents such as cationic surfactants that wipe out the oil wet layers rendering
the surface more water wet (Standnes and Austad 2000). A combined effect was also
noticed when a mixture of anionic surfactant and alumina NPs was used (Giraldo
et al. 2013).
A number of wettability alteration measurement techniques are used, such as
contact angle measurement (CAG), spontaneous imbibition (SI), zeta potential measurement (ZPM) and surface imaging tests (atomic force microscopy, SEM, NMR).
CAG is the measurement of the point at which oil and water interface meets at rock
surface. It is used to monitor the altering wettability of the surface by measuring the
shift of the affinity of rock surface toward one fluid than another in an advancing
manner (Morrow 1990). Magzhi et al. had used CAG approach to monitor change
in wettability of glass surfaces coated with SiO 2 nanofluid and oil with different