Enhancing the filtration properties of water-based drilling mud using a novel lignosulfonate–starch–silica nanocomposite (LS-SSNC) additive

Effective fluid-loss (FL) control remains a major challenge for water-based drilling muds, especially under high-temperature and high-pressure (HTHP) conditions. Conventional polymeric additives undergo thermal degradation and reduced sealing efficiency. To address this, a novel bio-based lignosulfonate–starch–silica nanocomposite(LS–SSNC) was synthesized via potassium persulfate-initiated acrylamide graft polymerization and evaluated as a multifunctional FL-control additive. The physicochemical properties of the nanocomposite(NC) were characterized using FTIR, TGA, SEM, BET, DLS, and Zeta potential analysis. Its mud performance was assessed through filtration and rheological tests at 25 and 185 °C. The optimum dose (0.2 g) reduced API FL by 36.4% and filter-cake thickness by 50% to the base mud. After thermal aging at 185 °C, the same formulation maintained excellent sealing performance, decreasing HPHT FL by 29.1% and filter-cake thickness by 59.3% relative to the base mud. Compared with a commercial additive at the same dosage, LS–SSNC further reduced HPHT FL by 15.1% and produced a 37.5% thinner filter cake. The NC also maintained stable rheological properties after thermal aging by moderating plastic viscosity (16 cP) and reducing the yield point by 44.1% and 10 s/10 min gel strengths by 83.3% and 85.0%, respectively, relative to the base mud. This confirmed effective clay stabilization under severe drilling conditions. The superior performance is attributed to the synergistic integration of lignosulfonate, acid-modified starch, and silica nanoparticles within a covalently grafted acrylamide network. This promotes electrosteric and likely chemisorptive stabilization, suppresses thermally induced clay flocculation, and forms a dense, low-permeability filter cake. These findings demonstrate that LS–SSNC provides a thermally stable alternative to conventional FL additives for advanced HTHP drilling operations.