A new caustic process for softening produced water for steam generation

Abstract

Oilfield produced water containing a high concentration of total dissolved solids (TDS) and hardness can successfully be softened for use as oilfield steam-generator feedwater. At the Belridge in Kern County, CA, the combination of caustic softening and weak-acid cation exchange has been used to soften produced water containing 11,000 TDS and 550-ppm hardness to <1-ppm hardness. The resultant sludge containing calcium carbonate and magnesium hydroxide is concentrated by centrifuging and is disposed of in a landfill. Compared to the use of conventional strong-acid ion exchange followed by weak acid or weak acid followed by weak-acid ion exchange systems, the process offers the benefits of lower capital and chemical costs, partial silica removal, and elimination of liquid waste discharge