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R. Sandeep et al.
3 Role of Nanomaterials in EOR
There are different types of nano-assisted EOR materials that have been applied in oil
fields for increasing the efficiency of the oil recovery processes. These can be used
as nanofluids/nanoparticles, nanoemulsions and nanocatalysts. All these nano-sized
materials have solved different purposes during the EOR recovery. A lot of different
mechanisms go into the process during the recovery of crude oil.
3.1 Nanofluids/Nanoparticles
The key reason for the nanoparticles having a tremendous potential in the field of
oil recovery is its size, which allows it to freely flow in the reservoir without getting
retained/adsorbed due to straining (Ko and Huh 2018). They have been used for a
wide variety of upstream and downstream oilfield applications with the synthesis in a
wide variety of size ranges and tailored with different surface coatings. NPs have been
employed as stabilizers, for improving the mobility of hydrocarbons, formation of
emulsions for better recovery, CO 2 foams, constituting formulation of drilling fluids
and altering rock surface wettability for improved oil recovery. Nanofluids, on the
other hand, are base fluids (water, oil or gas) that are composed of NPs ranging in
size below 100 nm in a colloidal suspension (El-Diasty and Ragab 2013; Sun et al.
2017). In general, these nanofluids are prepared in water or brine to improve the
efficiency of secondary flooding. Both NPs and nanofluids have been studied widely
and a number of mechanisms have been explained for their role in EOR.
3.1.1 Pore Throat Plugging
Plugging of the porous media channels occurs due to two different mechanisms, logjamming and mechanical entrapment (Skauge et al. 2010). These mechanisms can
prove beneficial to the NEOR application or can be a limiting process for the same.
Mechanical entrapment occurs when the dimensions of the pore throats are smaller
compared to the sizes of the injected EOR materials. However, the dimensions of
NPs are usually in nanometers and smaller compared to the sizes of the pore throats
that are in micrometers. Moreover, some of the NPs synthesized from metal ions are
larger in size and can block the pore channels resulting in reduced efficiency of NEOR
(Hashemi et al. 2013; Zamani et al. 2012). This issue can be avoided during the initial
evaluation of NEOR fluid in laboratory studies in oil field simulating sandpacks or
during core flooding studies.
Log-jamming, on the other hand, occurs during the flow of nanofluids and NPs
when the sizes of the pore throats are smaller than the sizes of the NPs (Sun et al.
2017). It leads to accumulation of the NPs at these pore throats creating a bulk
pressure difference with narrowing of the pore channels. This leads to the increase
R. Sandeep et al.
3 Role of Nanomaterials in EOR
There are different types of nano-assisted EOR materials that have been applied in oil
fields for increasing the efficiency of the oil recovery processes. These can be used
as nanofluids/nanoparticles, nanoemulsions and nanocatalysts. All these nano-sized
materials have solved different purposes during the EOR recovery. A lot of different
mechanisms go into the process during the recovery of crude oil.
3.1 Nanofluids/Nanoparticles
The key reason for the nanoparticles having a tremendous potential in the field of
oil recovery is its size, which allows it to freely flow in the reservoir without getting
retained/adsorbed due to straining (Ko and Huh 2018). They have been used for a
wide variety of upstream and downstream oilfield applications with the synthesis in a
wide variety of size ranges and tailored with different surface coatings. NPs have been
employed as stabilizers, for improving the mobility of hydrocarbons, formation of
emulsions for better recovery, CO 2 foams, constituting formulation of drilling fluids
and altering rock surface wettability for improved oil recovery. Nanofluids, on the
other hand, are base fluids (water, oil or gas) that are composed of NPs ranging in
size below 100 nm in a colloidal suspension (El-Diasty and Ragab 2013; Sun et al.
2017). In general, these nanofluids are prepared in water or brine to improve the
efficiency of secondary flooding. Both NPs and nanofluids have been studied widely
and a number of mechanisms have been explained for their role in EOR.
3.1.1 Pore Throat Plugging
Plugging of the porous media channels occurs due to two different mechanisms, logjamming and mechanical entrapment (Skauge et al. 2010). These mechanisms can
prove beneficial to the NEOR application or can be a limiting process for the same.
Mechanical entrapment occurs when the dimensions of the pore throats are smaller
compared to the sizes of the injected EOR materials. However, the dimensions of
NPs are usually in nanometers and smaller compared to the sizes of the pore throats
that are in micrometers. Moreover, some of the NPs synthesized from metal ions are
larger in size and can block the pore channels resulting in reduced efficiency of NEOR
(Hashemi et al. 2013; Zamani et al. 2012). This issue can be avoided during the initial
evaluation of NEOR fluid in laboratory studies in oil field simulating sandpacks or
during core flooding studies.
Log-jamming, on the other hand, occurs during the flow of nanofluids and NPs
when the sizes of the pore throats are smaller than the sizes of the NPs (Sun et al.
2017). It leads to accumulation of the NPs at these pore throats creating a bulk
pressure difference with narrowing of the pore channels. This leads to the increase