Synthesized silica-coated iron oxide nanoparticles and its application as rheology modifier in water-based drilling fluid

A successful drilling activity fundamentally depends on the characteristics of the drilling fluid. These fluids are responsible for the transportation of the drill cutting to the surface and maintaining the hydrostatic head in the well column. These characteristics properties are mainly dependent on the rheological parameters, which ensure the effectiveness of any drilling activity. In the current study, iron-oxide nanoparticles are coated with silica using the Modified Stober method. For the first time, application of this particle as a drilling fluid additive is monitored in the water-based mud system. The purpose of this particle was to enhance the rheological characteristics of the mud system. The particle was added in the water-based mud system in different concentrations ranging 0.1–0.5 wt% and rheological properties were examined. Results of the study reveal that no significant changes in mud weight were observed in any of the samples. The ΔMW was \(0.2\) $0.2$  ppg when the concentration varies from 0.1 to 0.5 wt%. Moreover, all the studied samples demonstrate pseudoplastic/shear thinning characteristics. Improvement in rheological behavior was observed at concentrations above 0.2 wt%. At lower weight percent, silica was unable to prevent the agglomeration of iron oxide particles; therefore, the performance of the particle suffers substantially. The yield point (YP) to plastic viscosity (PV) ratio considerably reduces and goes below the desired window of 0.75 at 0.1 wt%. The lower transport index (TI) ratio is responsible for creating problems during cutting transportation from the bottom of the wellbore up to the surface. All samples other than 0.1 wt% displayed TI ratio \(> 0.75\) $>0.75$ , thus indicates the higher efficiency of the silica-coated iron oxide in cutting transportation. In addition, no considerable changes were recorded in the gel strength (GS) with respect to time in any of the samples. It remains within the API recommended practices of 2–5 lb/100 ft² for \({\text{GS}}-10\mathrm{ \,sec}\) $\text{GS}-10\sec$ and 2–35 lb/100 ft² for \({\text{GS}}-10\mathrm{ \,min}\) $\text{GS}-10\min$ . All these findings in this study reveal that silica-coated iron oxide nanoparticles can be considered as an effective drilling fluid additive, which enhance the efficiency of water-based mud system.