The Influence of Nanoparticle Size, Concentration, and Functionalization on Drilling Fluid Filtration Properties

This research investigates the effect of the surface properties of silicon dioxide (SiO2) nanoparticles on the filtration properties of water-based drilling fluid. The nanoparticles were synthesized in-house using a one-step sol-gel method and functionalized into different charges. Different sizes, concentrations, and functionalization of water-based drilling fluid were subjected to standard API and HPHT filtration tests. Regression analysis and ANOVA were carried out to develop a model for future prediction and classify each independent variable's significance. The result shows that the positively charged nanoparticles had better filtration properties, as evidenced by the lower filtrate volume. Functionalization levels had minimal impact on filtration properties, and the effect of concentration was insignificant above 0.4v/v%. In terms of nanoparticle size, 120nm showed a more consistent result despite varying concentration and functionalization. In contrast, smaller nanoparticle sizes are more susceptible to changes in concentration and functionalization but could produce the least filtrate volume with the appropriate combination of concentration and functionalization. Filtrate analysis shows that about 25 to 28% of the drilling fluid nanoparticles can infiltrate the porous media. Furthermore, this study challenges existing models on the improvement of the filtration properties by using nanoparticles. While previous hypothesis relied on physical bridging mechanism, new evidence from this research suggests that the enhancement is primarily based on the surface properties of the nanoparticles. Specifically, the nanoparticles envelop the barite through monolayer adsorption, reducing the angularity and increasing the reaction sites with water molecules. This inhibits the mobility of the water molecules across the filter cakes, providing a novel understanding of the mechanisms underlying nanoparticle-enhanced filtration properties of drilling fluids. In summary, the filtration properties of water-based drilling fluid with nanoparticles are significantly influenced by the surface properties of the nanoparticles, with positively charged nanoparticles demonstrating superior performance in stable conditions.