Insightful study on the effect of zinc oxide nanoparticle diameter on the rheology of water base mud at elevated temperature

In deep water reservoir and more complex formation, the usage of special and advanced methods of drilling and production operation is considered vital to complete the drilling/production operation. However, they are considered costly and may not be environmentally friendly. Recently, nanoparticles have been introduced to drilling fluids to form a greater nanofluid with better rheological property, filtration rates and hydrogen concentration. This study is, therefore, aimed at investigating the effects of zinc oxide (ZnO) nanoparticles sizes on the rheological properties of water base mud (WBM) from surface to downhole conditions. Surface morphology and elemental composition of ZnO nanoparticles were also analyzed. The experiment was designed into three phases. In the first phase, the rheological properties of conventional WBM were tested, and in the second phase 0.5 wt% (3 g) of 10–30 nm of ZnO nanoparticles was added into WBM to test the rheological properties. The last phase included a bigger size of ZnO nanoparticles, which was 30–45 nm. A Consistometer was used to heat the fluid sample to different temperatures reaching up to downhole condition (90 °C). Viscosity, gel strength and yield point were measured using a rotational viscometer. Field emission scanning electron microscopy (JEOL JSM-7800F, Japan) attached with energy dispersive X-ray spectroscopy (EDXS, Oxford instrument, UK) were used to investigate surface morphology and elemental composition of ZnO nanoparticles. It was observed that the rheological properties of water base mud with zinc oxide nanoparticles were improved significantly by 40%–65%. The bigger size of zinc oxide nanoparticle, 30–45 nm, formed a more stable fluid at all conditions.