Investigation of Modified Silica Nanoparticles' Efficiency in Enhancing Oil Recovery - An Experimental Study
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As it has become difficult to discover new hydrocarbon resources, the focus hasshifted towards innovative enhanced oil recovery (EOR) technologies that extractmore 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 activatedsurface area, surface customization and are an easily producible base material. Several experimental methods were used to analyze the effectiveness of howmodified silica nanoparticles can improve oil recovery. The main objectives wereto determine the recovery factor from the nanoflooding phase by conductingcoreflooding experiments, and understand the significant EOR mechanisms thatoccur during transportation of nanoparticles in a porous medium. In addition,the wetting forces in an oil/nanofluid/solid system were analyzed by performingcontact angle measurements, and the interfacial interactions were studied throughemulsion tests. Coreflooding experiments were carried out at ambient conditions using BereaSandstone cores for both nanofluid-decane and nanofluid-crude oil systems. Threedifferent sizes of nano-structured silica particles were dispersed in synthetic NorthSea water (NSW) at 0.05 wt.%. The nanoparticles were named according totheir aggregated particle diameters of 72 nm (NS-S), 112 nm (NS-M) and 128nm (NS-L), where S, M and L denote small, medium and large, respectively.The resulting nanofluids were implemented as a tertiary recovery technique, afterwater injection. Waterflooding with NSW was conducted after the nanofloodingstage to determine the retention strength of the nanoparticles in the system. The main conclusions were that nanofluids produced incremental oil for all theseven displacement tests. The recovery mechanism was believed to be of a chemicalnature, as the smallest nanoparticle (NS-S) performed slightly better as an EORagent. However, the dominating EOR mechanism was likely the in-situ creationof unstable oil-in-water emulsions. Lastly, wettability alteration and interfacialtension reduction were considered to have a small impact on mobilization ofresidual oil. The effluent and influent analysis of fluid compositions and core propertiesshowed that NPs slowly retained in the system. However, the retention was foundreversible, as nanoparticles were not observed in the effluent crude oil. Coreflooding results have shown that application of nanoparticles provide anapproach to transcend the current EOR technology. In the nanoparticle-basedEOR research, no reservoir simulator has been developed. It was proposed inthis thesis that nano-EOR could be implemented to a reservoir simulator, bymodifying brine model options such as low salinity and surfactant flood.