Development of biodegradable triazine-chitosan nanocomposites enhanced with magnetic and silica nanoparticles for improved drilling fluid properties.

Despite continuous advancements in drilling fluid technology, achieving a balance between operational efficiency, environmental compatibility, and effective filtration control remains a persistent challenge. In this study, two novel chitosan-based nanocomposites-magnetic and silica nanoparticles functionalized with a triazine-chitosan network crosslinked by glutaraldehyde (Fe3O4@SiO2@melamine-chitosan and SiO2@melamine-chitosan)-were synthesized and systematically evaluated as additives for water-based drilling fluids. The performance enhancement is attributed to the synergistic interactions between the chitosan backbone, triazine-rich melamine units, and the nanoparticle cores, which collectively promote strong interfacial bonding, improved dispersion stability, and effective fluid-solid interactions. Rheological and filtration evaluations demonstrated a pronounced reduction in both American Petroleum Institute and high-pressure/high-temperature fluid loss with increasing nanocomposite concentration, with SiO2@melamine-chitosan exhibiting superior filtration control. At a nanocomposite concentration of 3000 ppm, the standard filtration loss decreased from 13 to 7 mL per 30 min, while the HPHT filtration loss was reduced from 30 to 16 mL per 30 min. These improvements are associated with enhanced wellbore stability and reduced formation damage through the formation of thinner, less permeable filter cakes. The filter cake thickness decreased from 2.5 to 1.5 mm. Moreover, the incorporation of the nanocomposites led to a notable increase in yield point-particularly in systems containing functionalized magnetic nanoparticles-indicating improved suspension capacity and flow control, while plastic viscosity remained largely unaffected. The yield point increased from 16 to 30 lb per 100 ft2, while plastic viscosity remained within the range of 16-20 cP. Overall, the combined benefits of enhanced rheological performance, effective filtration regulation, together with the environmentally favorable characteristics associated with chitosan-based materials, underscore the potential of these surface-engineered nanocomposites as potentially environmentally compatible and efficient additives for advanced water-based drilling fluid formulations.