Development and functional assessment of a polymer supported nanoscale iron hybrid for sustainable enhancement of water based drilling fluids.

Eco-friendly biopolymers in water-based drilling fluids often suffer from thermal degradation and inadequate filtration control under harsh downhole conditions. To overcome these limitations, this study aimed to develop a high-performance, sustainable hybrid nanocomposite that synergistically combines the structural resilience of biopolymers with the mechanical strength and pore-plugging capabilities of metallic nanoparticles. A ternary nanocomposite (IRON-NC) was synthesized via an in-situ reduction-stabilization method, embedding nanoscale zero-valent iron (nZVI) within a crosslinked chitosan and carboxymethyl cellulose (CMC) matrix. The material's morphology, chemical interactions, and electrokinetic properties were characterized, followed by comprehensive rheological and filtration evaluations under both standard and high-pressure/high-temperature (HPHT) conditions. Unlike standalone biopolymer additives, this hybrid architecture leveraged strong electrostatic repulsion (zeta potential of -48.5 mV) and robust polymer-metal bonding to ensure uniform dispersion and exceptional thermal reliability. At a remarkably low optimal dosage of 1000 ppm, IRON-NC induced pronounced shear-thinning behavior, increasing plastic viscosity to 37.6 cP and yield point to 13 Pa to ensure effective cuttings suspension. Furthermore, the nZVI-reinforced matrix facilitated the deposition of a highly compact, structurally resilient filter cake, reducing both API and HPHT fluid loss by 43-47% compared to the base fluid. The synergistic integration of nZVI with the chitosan-CMC network effectively resolves the thermal and mechanical vulnerabilities associated with conventional eco-friendly additives. Ultimately, IRON-NC presents a highly efficient, multifunctional, and environmentally compliant solution for improving rheology, stability, and fluid loss control in advanced drilling operations.