Optimizing Metal-Removal Processes for Produced Water With Electrocoagulation

gas basin. For example, recycled produced water is less than 10% of the total water used to drill and fracture in the Barnett, Fayetteville, and Haynesville shale plays. However, the fraction of water recycled is significantly higher in the Marcellus play—greater than 90% of the total water used (Mantell 2011). Although treatment methods have been developed to recycle produced water for subsequent fracturing operations, widespread adoption of these methods is often limited by costs. Important treatment aspects for fracturing-water reuse include particle removal, reduction of scale-forming metals, and disinfection. Removal of total dissolved solids (TDS) is expensive and therefore avoided, if possible. Fracturing fluids have been developed that are compatible with high TDS concentrations, but the other objectives (solids reduction, scale control, and bactericide) almost always need to be satisfied. The focus of this study was to examine the metal-removal processes associated with reducing scaling potential by use of laboratory-scale data and chemical-equilibrium modeling, with the goal of optimizing chemical use and minimizing cost.