Enhancement of the heat capacity of water-based drilling fluids for deep drilling applications

Formulation of drilling fluids with appropriate thermal properties is needed for cooling the drill bit, especially under high-pressure high-temperature conditions. Using proper additives for drilling fluid preparation can decrease the drill bit replacement costs in deep drilling operation. Nanoparticles have been extensively investigated as drilling fluid additives for thermal conductivity enhancement. However, studies of drilling nanofluid specific heat capacity are limited in the literature. As increase of thermal conductivity is necessary but not sufficient for achieving high performance heat transfer. This study was carried out to complement existing research by measuring the specific heat capacity of water-based drilling fluids containing nanoparticles. For this purpose, three types of metal oxide nanoparticles were added to an industrial formulated drilling fluid. Transmission electron microscopy was used to investigate nanoparticles morphology and X-ray diffraction was applied to determine nanoparticles purity. A simple device was designed, constructed and calibrated to measure the drilling fluid heat capacity. The experimental data revealed that the heat capacity of the drilling fluid can be enhanced by adding nanoparticles due to increased surface atomic contributions. The highest increase in heat capacity, i.e., 4.8%, was observed in the presence of 0.5 wt% titania nanoparticles. The results obtained from the measurement of rheological properties indicated that viscosity, yield point, and gel strength of the drilling nanofluid are highly dependent on nanoparticle type, size and concentration. Maximum increase obtained in rheological properties was 29% in plastic viscosity by adding titania nanoparticles and 37% in yield point for silica nanoparticles, at a concentration of 0.5 wt%. It was shown that nanoparticles may enhance thermal and rheological properties of drilling fluids and can be used as an efficient additive for deep drilling operation.