Rheological and thermal property of KH570-modified nano-SiO₂ grafted xanthan gum and its application in drilling...

Xanthan gum (XG), recognized for its environmentally friendly properties and versatile capabilities, has been studied for drilling fluid applications. However, its limited solubility and thermal stability restricts its broader use. In this study, a modified XG derivative, XG-g-KH570 modified SiO₂, was synthesized by grafting XG with KH570-modified nano-SiO₂. The modified product exhibited lower molecular weights with M_n and M_w of 3.00 × 10⁵ g/mol and 3.77 × 10⁵ g/mol, respectively. Its pyruvate and acetyl contents decreased to 2.72 % and 1.68 %, respectively. Meanwhile, XG-g-KH570 modified SiO₂ showed a higher branching degree of 45.3 % based on methylation analysis. In terms of performance, XG-g-KH570 modified SiO₂ exhibited improved water solubility. XG-g-KH570 modified SiO₂ demonstrated superior high-temperature and high-salinity performance, retaining high viscosity retention and viscoelasticity. Additionally, XG-g-KH570 modified SiO₂ exhibited a markedly reduced fluid loss of only 3.4 mL at 150 °C, compatible with conventional desulphonated drilling fluids. Furthermore, its high-temperature thickening and fluid loss control mechanisms was found to be associated with an enhanced cross-linked network structure based on the zeta potential and particle size distribution under high-temperature and salinity conditions. These results represent a promising advancement in the field of biomolecular drilling fluid additives, providing an efficient and eco-friendly solution for the oil and gas industry.