Use of Evaporation for HeavyOil Produced Water Treatment

摘要

Heavy oil recovery processes have traditionally used"once through" steam generators (OTSG) to producehigh pressure steam for injection into geologicalformations containing heavy oil. The heat given up by thecondensing steam fluidizes the heavy oil and allows theoil/water mixture to be brought to the surface. The oil isrecovered as product and the water, referred to asproduced water, is de-oiled and treated for feedwater tothe OTSG. The typical treatment method for producedwater is warm or hot lime softening (WLS or HLS),filtration, and weak acid cation exchange (WAC).An alternative method of produced water treatment isvertical tube, falling film, vapor compressionevaporation. This method: (1) eliminates physicalchemicalproduced water treatment, (2) results in lowerlifecycle costs, (3) does not produce any softener sludgefor disposal, (4) minimizes the number and volume ofwaste streams requiring disposal, (5) requires fewer maintenance materials and less maintenance labor, (6)reduces the required amount of produced water de-oilingequipment, (7) dramatically increases OTSG feed waterquality, improving OTSG reliability, (8) and providesincreased system availability and reliability. For steamassisted gravity drainage (SAGD) processes, whichrequire 100% quality steam, it has the added advantageof producing water of sufficient quality for use instandard packaged boilers in lieu of OTSG. Packagedboilers are less expensive than OTSG, produce a muchsmaller liquid blowdown stream, and results in a boilerfeed system which is 20% smaller than that of an OTSG.