The produced waters from Steam Assisted Gravity Drainage (SAGD) facilities are characterized by low concentrations of both total hardness (TH) and total dissolved solids (TDS) and high silica concentrations. Treatment of these waters to provide feed-water suitable for Once Through Steam Generators (OTSG) has traditionally included either hot or warm lime softeners (HLS/WLS) and ion exchange. The primary function of the lime softening process is for silica removal.
A proposed alternate process that utilizes ion exchange only and depends on the premise that provided the divalent and trivalent cations are reduced to the parts per billion (ppb) level, will allow the OTSG to operate at high silica concentrations. This process eliminates the need for a lime softening stage and savings in capital and operating costs are realized.