Field and Laboratory Evaluation of Potassium Chloride Polymer Mud for Drilling Stability in Clay‐Rich Formations of Southeastern Türkiye

ABSTRACT Southeastern Anatolia, Türkiye's largest oil reserve region, faces long‐standing challenges in oil and gas drilling due to severe instability in clay‐rich formations. Interaction between clay minerals and freshwater triggers hydration and osmotic swelling, which frequently results in wellbore collapse, circulation losses, nonproductive time, and significant equipment damage. Overcoming these issues requires drilling fluids specifically engineered to stabilize reactive clays under complex downhole conditions. This study presents a field‐scale validation of potassium chloride (KCl) polymer‐based drilling fluids, designed to enhance wellbore stability in the Germav and Kastel formations of Areas A and B. Daily monitoring of mud properties, conducted in accordance with API standards, was integrated directly with drilling operations in wells A‐1 and B‐1, while 41 supplementary laboratory experiments provided additional verification of mud performance. The findings demonstrated that KCl polymer mud markedly improved wellbore stability under real operational conditions. In A‐1, KCl mud outperformed conventional lignosulfonate fluids, limiting clay contamination to only 2.5 lb/bbl after passing 2030 m and enabling smooth, problem‐free drilling to 2209 m. In B‐1, logistical challenges and a 5 lb/bbl increase in clay underscored the importance of maintaining an adequate potassium concentration; nevertheless, KCl mud successfully mitigated collapse risks following mud loss events by restoring circulation and hydrostatic balance. Overall, the study provides one of the first comprehensive validations of KCl polymer mud performance at the field scale in Southeastern Anatolia, delivering novel insights for drilling fluid optimization. These findings confirm the reliability, safety, and practicality of KCl polymer systems for mitigating clay‐related instabilities in challenging reservoirs when supported by appropriate engineering design and application.