Optimizing the Filtration Properties of Water-Based Drilling Mud with a Novel Lignosulfonate–Starch–Silica Nanocomposite (LS-SSNC) Additive

Abstract

Abstract Effective fluid loss (FL) control is essential for maintaining wellbore stability and drilling efficiency in water-based drilling muds (WBDM), particularly under high-temperature, high pressure (HTHP) conditions where conventional additives exhibit limited performance. This study evaluates a novel bio-based lignosulfonate–starch–silica nanocomposite (LSSSNC) as a fluid-loss control additive for WBDM. API and high-pressure high-temperature (HPHT) filtration tests were conducted to assess filtrate loss volume (FLV) and filter cake thickness (FCT) under varying concentrations of lignosulfonate (LS), starch, and silica nanoparticles (SNP), and at elevated temperatures. Optimization was performed using response surface methodology (RSM) based on a Box–Behnken design (BBD), considering LS (0.5 to 10 g), starch (2.5 to 7.5 g), SNP (0.5 to 15 g), and temperature (25 to 185 °C) as independent variables, while FLV and FCT were the dependent responses. The developed regression models were statistically significant (p < 0.005) with strong predictive capability (R2 = 0.95 for FLV and 0.92 for FCT). The optimized formulation (LS = 5.25 g, starch = 5.0 g, SNP = 7.75 g at 185 °C) achieved up to 50 % reduction in HPHT FL and 62.5 % reduction filter cake thickness at 0.2 g additive concentration under 500 psi, while a 36.4 % FLV and 50 % FCT reduction was observed under API conditions. Experimental validation closely agreed with model predictions. The improved performance is attributed to enhanced colloidal stability, dual stability mechanism, and effective synergy between components, thus forming a thin, low-permeability, and mechanically resilient filter cake. These results demonstrate that LSSSNC is a promising high-performance additive for fluid-loss control in WBDM under severe HTHP drilling conditions.