Abstract

Facilities for steam-assisted gravity drainage (SAGD) require vessels for oil/water emulsion separation, water treatment, and steam generation. Gravity separation is generally used to separate emulsion, with the requirement of diluent and a demulsifier chemical addition. Treatment of emulsion and water constitute a major capital component and operating cost, and generally involves skim tanks, gas flotation, filtration, warm lime softening, and ion exchange. Most facilities use once-through steam generators (OTSGs) to generate steam because of their ability to handle water with a higher concentration of dissolved solids relative to package boilers.

Heins and Peterson suggested an alternative method for water treatment utilizing a vertical tube falling film evaporator (Heins and Peterson 2003). Water vapour is compressed, raising its temperature, and transfers its latent heat to the untreated water. The condensed water is recovered as high quality distillate and the vapour is recirculated. Benefits of this process include reduced water treatment costs and increased boiler feed water quality, allowing for use of package boilers instead of OTSGs and reduced liquid discharge requiring disposal.

The authors propose an extension of the evaporative water treatment process whereby the evaporator acts as both a water purification and emulsion separation unit. This process can be retrofitted to current SAGD operations and, in addition to the benefits of evaporative water treatment, can reduce or eliminate the need for diluent and chemical addition for emulsion separation.

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