Performance Evaluation of an Activated Greek Palygorskite in High-Salinity and High-Hardness Water-Based Drilling Fluids

The performance of conventional bentonite-based drilling fluids is severely compromised in high-salinity and high-hardness brines, creating a need for salt-tolerant viscosifiers. This work provides a comprehensive performance evaluation of an activated palygorskite sourced from the Ventzia basin in Greece to be used as a high-performance additive for water-based drilling fluids. Six raw clay samples were mechanically processed and activated via extrusion and chemically treated with 2.25% MgO. Their rheological behavior and filtration properties were systematically investigated in three aqueous environments, (i) deionized water, (ii) API-standard salt water, and (iii) API-standard high-hardness salt water. The performance was benchmarked against that of commercial palygorskite products. The results demonstrated that the selected activated Greek samples exhibited excellent rheological properties, including higher viscosity, yield point, and thixotropic gel strength, comparable to those of the commercial benchmark. While the fluid’s rheology was suppressed by increasing salinity due to the flocculation of co-existing smectite, the best-performing Greek clays maintained a significant advantage, developing exceptionally robust gel structures critical for solid suspension in harsh conditions. Crucially, the same smectite flocculation mechanism proved highly beneficial for filtration control, leading to a significant reduction in fluid loss and the formation of a thin filter cake, particularly with the high-hardness brine. The findings confirm that activated Greek palygorskite is a technically viable, high-performance alternative to imported commercial materials, offering a sustainable solution for formulating resilient drilling fluids for challenging environments.