Compatibility of Completion Fluids with Formation Water During Workover Operations

Workover operations play a vital role in extending the productive life of oil and gas wells. Completion fluids play a critical role in maintaining wellbore stability, minimizing formation damage, and enhancing hydrocarbon recovery. This study evaluates the compatibility of common completion fluids (NaCl, KCl, and CaCl₂ brines) with synthetic formation water to optimize fluid selection and minimize formation damage during workover operations. Laboratory-grade salts were used to prepare the brines, which were mixed with synthetic formation water at volume ratios ranging from 1:9 to 1:1. The mixtures were conditioned at temperatures from room temperature (~25°C) to 95°C for 24 hours. Key fluid properties measured included pH, electrical conductivity, salinity, total dissolved solids (TDS), and resistivity, with visual observation for precipitation. NaCl and KCl mixtures exhibited linear trends in all measured properties, indicating good compatibility and stability. In contrast, CaCl₂ mixtures showed non-linear decreases in conductivity, salinity, and TDS at higher temperatures (70–95°C), accompanied by CaCO₃ precipitation. KCl is recommended as the preferred fluid for carbonate reservoirs to reduce scaling risk