Design and Performance Assessment of a Polymer-Based Filtration-Control System for High-Temperature, High-Density Water-Based Drilling Fluids

A sustainable polymer-based filtration control system was developed for high-temperature, high-density water-based drilling fluids. The system’s rheological stability, filtration performance, and filter cake properties were evaluated under varying conditions of temperature, salinity, and density. The drilling fluid density ranged from 1.80 to 2.20 g/cm3, the temperature from 25 to 150 °C, and the NaCl mass fraction w(NaCl) = 5–20%. The results indicated that increasing fluid density resulted in a progressive increase in apparent and plastic viscosities (from 42.6/28.4 mPa·s to 65.1/47.9 mPa·s), while the yield point remained relatively stable (14.2–17.2 Pa), suggesting that high solid loading enhanced viscous dissipation without inducing structural stiffening. Filtration loss increased moderately with temperature (6.8–12.3 mL at 25–150 °C) and salinity (6.8–10.7 mL at w(NaCl) = 5–20%), whereas it decreased significantly with increasing density (13.1–9.4 mL at 1.80–2.20 g/cm3), indicating a density-dominated filtration regime. At 120 °C, w(NaCl) = 12%, and 2.00 g/cm3, the developed system achieved a low filtration loss of 8.4 mL, outperforming three representative conventional filtration-control systems, including starch-based, sulfonated asphalt-based, and polymer-based technologies. Filter cake analysis revealed that increasing density facilitated the packing of multi-scale solids, reducing filter cake thickness from 1.62 mm to 0.98 mm and permeability from 1.34 × 10−15–4.05 × 10−16 m2, while significantly improving resistance to erosion and compression. These findings demonstrate that the combination of interfacial stabilization and filter cake densification offers a robust and controllable filtration solution for high-temperature, high-density drilling environments, presenting a promising approach for drilling fluid systems in challenging conditions.