An Experimental Investigation of Enhanced Oil Recovery Mechanisms in Nanofluid Injection Process
MetadataShow full item record
Nanotechnology is recently proposed to increase oil recovery in some literature. Nanoparticles, as part of nanotechnology, are chosen as novel enhanced oil recovery (EOR) agent. Compared with other chemical EOR agents, silica nanoparticles offer several benefits, such as good stability in suspension, green material and environmentally friendly, easier surface modification and low cost. Another important advantage is that size of nanoparticles is much smaller than pore throat, and giving them a good ability to permeate a reservoir. The objective of this thesis is to reveal EOR mechanisms behind nanofluid flooding process and find out the main EOR mechanism of nanofluid. This is a fundamental research involving investigation of effect of nanoparticles on fluid-fluid interaction and fluid-rock interaction. Two different types of nanoparticles and three different concentrations of nanofluid were employed in this thesis. And the proposed EOR mechanisms of nanofluid include interfacial tension (IFT) reduction, wettability alteration, disjoining pressure, emulsification and pore channel plugging. Several laboratory experiments were designed to examine each mechanism and its effect on EOR. Visualization flooding experiments with a glass micromodel were conducted to observe nanoparticles displacing crude oil behavior in pore level as well as nanoparticles adsorption and retention inside porous media. The effect of nanoparticles on oil recovery was also investigated. IFT and contact angle between nanofluid and crude oil was measured to see influences of nanoparticles on fluid-fluid interaction and fluid-rock interaction. In wettability alteration experiments, wettability index of three different wettability (oil wet, neutral wet and water wet) core plugs treated by hydrophilic nanoparticles were measured to see ability of nanoparticles adsorption on altering core’s wettability. The effect of different nanoparticles’ type and concentration on wettability alteration was also investigated. And the basic mechanism of nanoparticles altering wettability was discussed. When nanoparticles are injected into Berea sandstone, adsorption on pore wall will happen. In order to better understand this phenomenon, nanoparticles adsorption and transport experiments were performed for three different wettability core plugs. Nanoparticles concentration of effluent was measured to plot adsorption curve and pressure drop across core was also recorded to investigate the effect of nanoparticles adsorption on permeability change. Core flooding experiments with nanofluid were conducted to study wettability alteration with crude oil present inside core. Core plugs with and without initial water saturation were employed to find out the role of water saturation during wettability alteration. The EOR mechanisms for different types of nanoparticle were further discussed. The overall investigations from all experiments showed that nanoparticles have promising potential for EOR in the future. And the EOR mechanisms of nanofluid is complicated and comprehensive, the most possible situation is that several mechanisms work simultaneously during nanofluid flooding. And from the results of the nanofluids used in this experimental work, the mechanisms of wettability alteration might be the most important and main EOR mechanism for nanofluid flooding.