Technical Advancements in SAGD Evaporative Produced Water Treatment

There has been a shift away from the use of warm lime softening (WLS) and weak acid cation (WAC) ion exchange for produced water treatment to the use of mechanical vapour compression (MVC) evaporation followed by high pressure drum-type boilers. Approximately 18 steam assisted gravity drainage (SAGD) produced water evaporators are operating or are in various stages of construction in Alberta and overseas. Since the commissioning of the first such evaporators in 2002, many technical advancements have occurred which have resulted in reduced operating costs, improved reliability, reduced scaling and fouling potential, improved distillate quality and improved boiler feed quality for steam generation. This paper provides details of the technical advancements in evaporative produced water treatment based on full-scale operating data and lessons learned. It also presents improved evaporator configurations, discusses improvements in contaminant reduction and scale prevention systems, demonstrates how capital and operating costs can be drastically reduced as compared to earlier evaporator system designs, and provides recent advancements in modularization, evaporator disposal treatment, deoiling, membrane preconcentration, and zero discharge solids drying techniques.