Xanthan gum (XG) is widely used as a viscosifier in drilling fluids; however, its structure degrades at high temperatures, altering its rheological properties. This study investigates the thermal degradation of XG, focusing on kinetic and rheology with aging. Thermogravimetric analysis showed mass loss at 79 and 277 °C, related to water and volatiles release. Isoconversional models (Ozawa, Starink, KAS, and Kissinger) fit well for 30%–50% conversion (loss of volatiles), with an average activation energy of 176 KJ mol ⁻¹ . z ‐Master plot analysis suggested degradation begins with rapid nucleation in side chains, exposing the main chain. Increased thermal energy induced chain fragmentation into smaller reactive centers, accelerating propagation and following third‐order kinetics. Rheological analysis confirmed pseudoplastic behavior, with flow indices between 0.29 and 0.56. Degradation intensified with temperature, especially above 140 °C in static aging and above 100 °C in dynamic aging, where shear viscosities approach 1 mPa.s. Under dynamic aging conditions, degradation was more severe due to side chains loss and exposure of the backbone. These findings highlight the thermal and mechanical vulnerabilities of XG in high‐temperature drilling environments.

This study explores the reuse of Ornamental Stone Waste (OSW) in water-based drilling fluids, investigating its potential as a substitute for bentonite. To enhance stability and rheology, OSW particles were functionalized with terephthalic acid (TPA) and combined with xanthan gum (XG). Characterization confirmed successful surface modification, with increased stability at a basic pH. However, rheological analysis showed that the physical mixing of OSW-TPA with XG resulted in low viscosity and poor yield stress, indicating weak interactions. All formulations exhibited shear-thinning behavior. Future work will focus on promoting chemical interactions to form nanocomposite structures and improve fluid performance.