Enhanced thermal conductivity and reduced viscosity of aegirine-based VR/VGO nanofluids for enhanced thermal oil recovery application

The depleting of the available conventional energy supplies together with an industrial shift towards unconventional resources like heavy oil/bitumen has become more pronounced. The steam-based heating methods are primarily used by the oil industry for the heavy oil/bitumen recovery. However, the thermal recovery methods are energy-intensive and have limited applications, especially for both thin and deep reservoirs. Therefore, there is a high priority need to investigate alternative approaches. To date, the most progressive alternative technique that has proven its potential during pilot-plant tests is nanocatalytic in-situ heavy oil/bitumen upgrading via hot-fluid injection. Hence, the continual improvement of this technique is of utmost importance. This study aims to propose a new injecting nanofluid system suitable for high-temperature injection into the reservoir with consecutive heavy oil/bitumen upgrading and recovery. Here we report a new type of copper-based nanofluid using a blend of vacuum gas oil (VGO) and vacuum residue (VR) as the mother solvent. The nanoparticles were prepared by low-temperature hydrothermal synthesis route. Their detailed surface, morphology and size characterizations were achieved by X-ray diffraction, dynamic light scattering and scanning electron microscopy. The stable nanofluids were prepared by dispersing copper-based nanoparticles in a mixture of VGO and VR, at different ratios and temperatures. A set of measurements to determine the thermal conductivity and viscosity of the nanofluid with different loading of nanoparticle were performed. The thermal conductivity values of nanofluid systems are substantially higher than that of the base fluids. The nanofluid for 2 wt% of copper-doped aegirine nanoparticles dispersed in VGO and VGO/VR mixture exhibits a maximum thermal conductivity of 20% and 24%, respectively. It was found that the thermal conductivity of nanofluids increases with decreasing the hydrodynamic particle size. Moreover, the presence of chemo-physical interactions between nanoparticles and base fluid further enhances the thermal conductivity. Also, the temperature augmentation in a range from 80 to 110 degrees C exhibited a positive effect on thermal conductivity enhancement of vacuum residue-based nanofluid system. This particular nanofluid may find potential applications in enhancing heavy oil upgrading and recovery.