| dc.description.abstract | As it has become difficult to discover new hydrocarbon resources, the focus has
shifted towards innovative enhanced oil recovery (EOR) technologies that extract
more oil out of producing reservoirs. The addition of modified silica nanoparticles
(NPs) to the injected water shows promise as a cost-effective EOR technique.
Compared to other additives, nanoparticles have the advantage of a large activated
surface area, surface customization and are an easily producible base material.
Several experimental methods were used to analyze the effectiveness of how
modified silica nanoparticles can improve oil recovery. The main objectives were
to determine the recovery factor from the nanoflooding phase by conducting
coreflooding experiments, and understand the significant EOR mechanisms that
occur during transportation of nanoparticles in a porous medium. In addition,
the wetting forces in an oil/nanofluid/solid system were analyzed by performing
contact angle measurements, and the interfacial interactions were studied through
emulsion tests.
Coreflooding experiments were carried out at ambient conditions using Berea
Sandstone cores for both nanofluid-decane and nanofluid-crude oil systems. Three
different sizes of nano-structured silica particles were dispersed in synthetic North
Sea water (NSW) at 0.05 wt.%. The nanoparticles were named according to
their aggregated particle diameters of 72 nm (NS-S), 112 nm (NS-M) and 128
nm (NS-L), where S, M and L denote small, medium and large, respectively.
The resulting nanofluids were implemented as a tertiary recovery technique, after
water injection. Waterflooding with NSW was conducted after the nanoflooding
stage to determine the retention strength of the nanoparticles in the system.
The main conclusions were that nanofluids produced incremental oil for all the
seven displacement tests. The recovery mechanism was believed to be of a chemical
nature, as the smallest nanoparticle (NS-S) performed slightly better as an EOR
agent. However, the dominating EOR mechanism was likely the in-situ creation
of unstable oil-in-water emulsions. Lastly, wettability alteration and interfacial
tension reduction were considered to have a small impact on mobilization of
residual oil.
The effluent and influent analysis of fluid compositions and core properties
showed that NPs slowly retained in the system. However, the retention was found
reversible, as nanoparticles were not observed in the effluent crude oil.
Coreflooding results have shown that application of nanoparticles provide an
approach to transcend the current EOR technology. In the nanoparticle-based
EOR research, no reservoir simulator has been developed. It was proposed in
this thesis that nano-EOR could be implemented to a reservoir simulator, by
modifying brine model options such as low salinity and surfactant flood. | en |
