Considering low recovery rate and techniques uncertainties faced by traditional enhanced oil recovery (EOR) techniques, especially the methods of chemical and engineered water flooding, this thesis develops emerging nanotechnologies for EOR applications. Five areas were studied ranging from water flooding, surfactant flooding, microemulsion flooding, polymer flooding to nanoparticle mobility studies.
Firstly, rutile ellipsoid TiO2 nanoparticles (NPs) were synthesised and stabilised by tri-sodium citrate dihydrate for brine flooding in water-wet Berea sandstone cores. The results showed that the oil recovery depended on NPs concentration and volume injected: 10 ppm TiO2 had the highest total oil recovery while 500 ppm had the highest increment recovery after the breakthrough. The EOR effects were attributed to the log-jamming effects and probably wettability change towards water wetting.
Following this, nanoparticles were proposed as surfactant carrier to address the issue of excess adsorption of surfactants during a chemical EOR process. The adsorption of surfactants blend of 25% anionic alkylaryl sulfonates (XOF-25S) and 75% alcohol ethoxylated was found being reduced by commercial TiO2 nanoparticle in dolomite and silica cores. The surfactant concentration was determined by chemical oxidation demand (COD) method. Surfactant adsorption in rock grain matrix was found to have a direct relationship with the nanoparticle retention.
To address the problems associated with conventional microemulsion flooding, in-situ synthesised iron oxide NPs were proposed to stabilize the oil-in-water microemulsion texture, prevent surfactant from detaching from the interface and forming viscous phase in produced oil, and mobilize more oil as increasing the particle concentration. Core flooding experiments showed the promise of the nanoparticle-engineered microemulsion.
To address the polymer degradation issue at high temperature during a traditional polymer-flooding, SiO2 NPs were used to improve the salt-tolerance, rheological properties and thermal stability of hydrolysed polyacrylamide (HPAM), as well as its EOR potential. The EOR experiments at 50 oC showed that the oil recovery was increased to 69.6 % with 0.5 wt% HPAM seeded with 0.6 wt% SiO2 NPs, compared to a plain brine flooding efficiency of 56.2 %.
Finally, the migration properties of nanoparticles were investigated in columns packed with glass beads, saturated with brine at various salinities up to API standard. The luminescent carbon particles were used and a nearly full breakthrough behaviour (100% of C/C0) was observed even in API brine for 5-nm carbon dots. Controversially, the breakthrough behaviour was discounted in calcite limestone matrix. The good thermal stability and mobility enable the carbon dots act as reservoir sensor in sandstone rock, and detection of the saturation degree of hydrocarbon in sandstone core was demonstrated.
The work conducted in the thesis showed the great promise of nanoparticles for EOR applications at the laboratorial scale, and future work shall be planned at large scales.
