Application of Nanoparticles-Based Technologies in the Oil …
267
viscosities (Maghzi et al. 2012). They had reported that the wettability was altered
toward water-wet state regardless of the viscosity of the oil on the surface.
SI monitors determine the ability of the wetting phase to displace the non-wetting
phase (Mohammed and Babadagli 2015). ZPM monitors change surface charges; a
shift from positive to negative potential reflects the altering wettability of the surface during treatments with anionic surfactants (Hirasaki and Zhang 2004). Imaging
techniques help giving insights of the microscopic view of the surface to monitor change in wettability (Karimi et al. 2012; Schembre et al. 2006). For example,
Karimi et al. had shown using SEM images and EDX (energy-dispersive X-ray) that
NPs get adsorbed on the surface of calcite forming nano-textured surfaces (Karimi
et al. 2012). Similarly, in order to visualize the surface of rock after treatment with
NPs, Al-Anssari et al. used SEM–EDS and AFM measurements and observed the
homogenous distribution of NPs after nanomodification of surface (Al-Anssari et al.
2016; Nikolov et al. 2010).
Amott test and core displacement tests are also used for the evaluation of the
wettability alteration characteristics. Amott test involves the measurement of the
volume of fluids that is spontaneously or forcibly imbibed by a rock sample. It
is measured by calculating wettability index (I w ) as mentioned in the following
equation:
I w =
V o1
V o1 + V o2
−
V w1
V w1 + V w2
where V o and V w denote the volume of oil imbibed and the volume of water drained
during the process, respectively. The subscript “1” represents spontaneous process
and “2” means forced displacement process. The values of I w range from −1, representing as complete water-wet state, 1 as oil-wet to 0 as neutral wettability of the
surface (Sun et al. 2017). Li et al. had performed Amott test to monitor the change in
wettability of rock surface after treatment with SiO 2 NPs (Li et al. 2013, 2015). They
had reported the change in wettability of sandstone surface from oil wet to neutral
wet. Roustaei et al. had used SiO 2 NPs for altering wettability of carbonate cores
and also found similar results (Roustaei and Bagherzadeh 2015). The results were
consistent when Al-Anssari et al. had used SiO 2 nanofluids and found the wettability
altered to a mixed wet state (Al-Anssari et al. 2016).
Core wettability also helps determine the wettability alteration by analyzing the
changes the residual water saturation, oil relative permeability and the point where
the oil and water relative permeability are equal (Sun et al. 2017).
3.1.4 Improving Sweep Efficiency
Craig in 1971 has suggested that the oil recovery efficiency depends upon volumetric
sweep efficiency, which can be defined by the following equation (Craig 1971):
E r = E d × E v
267
viscosities (Maghzi et al. 2012). They had reported that the wettability was altered
toward water-wet state regardless of the viscosity of the oil on the surface.
SI monitors determine the ability of the wetting phase to displace the non-wetting
phase (Mohammed and Babadagli 2015). ZPM monitors change surface charges; a
shift from positive to negative potential reflects the altering wettability of the surface during treatments with anionic surfactants (Hirasaki and Zhang 2004). Imaging
techniques help giving insights of the microscopic view of the surface to monitor change in wettability (Karimi et al. 2012; Schembre et al. 2006). For example,
Karimi et al. had shown using SEM images and EDX (energy-dispersive X-ray) that
NPs get adsorbed on the surface of calcite forming nano-textured surfaces (Karimi
et al. 2012). Similarly, in order to visualize the surface of rock after treatment with
NPs, Al-Anssari et al. used SEM–EDS and AFM measurements and observed the
homogenous distribution of NPs after nanomodification of surface (Al-Anssari et al.
2016; Nikolov et al. 2010).
Amott test and core displacement tests are also used for the evaluation of the
wettability alteration characteristics. Amott test involves the measurement of the
volume of fluids that is spontaneously or forcibly imbibed by a rock sample. It
is measured by calculating wettability index (I w ) as mentioned in the following
equation:
I w =
V o1
V o1 + V o2
−
V w1
V w1 + V w2
where V o and V w denote the volume of oil imbibed and the volume of water drained
during the process, respectively. The subscript “1” represents spontaneous process
and “2” means forced displacement process. The values of I w range from −1, representing as complete water-wet state, 1 as oil-wet to 0 as neutral wettability of the
surface (Sun et al. 2017). Li et al. had performed Amott test to monitor the change in
wettability of rock surface after treatment with SiO 2 NPs (Li et al. 2013, 2015). They
had reported the change in wettability of sandstone surface from oil wet to neutral
wet. Roustaei et al. had used SiO 2 NPs for altering wettability of carbonate cores
and also found similar results (Roustaei and Bagherzadeh 2015). The results were
consistent when Al-Anssari et al. had used SiO 2 nanofluids and found the wettability
altered to a mixed wet state (Al-Anssari et al. 2016).
Core wettability also helps determine the wettability alteration by analyzing the
changes the residual water saturation, oil relative permeability and the point where
the oil and water relative permeability are equal (Sun et al. 2017).
3.1.4 Improving Sweep Efficiency
Craig in 1971 has suggested that the oil recovery efficiency depends upon volumetric
sweep efficiency, which can be defined by the following equation (Craig 1971):
E r = E d × E v