Patent ID: 7428926

Claim:
A process for producing steam for downhole injection in the recovery of heavy oil, said process comprising: (a) providing an oil/water mixture gathered from an oil/water collection well; (b) separating oil from said oil/water mixture to provide an oil product and a produced water product containing oil therein; (c) de-oiling said oil containing produced water product to at least partially provide an evaporator feedwater stream, said evaporator feedwater stream comprising water, dissolved gases, and dissolved solutes, said dissolved solutes comprising silica; (d) providing an evaporator having a plurality of heat transfer elements, a liquid containing sump reservoir, and a recirculating pump to recycle a concentrated brine from said sump reservoir to said plurality of heat transfer elements; (e) injecting said evaporator feedwater stream into said evaporator and evaporating a portion of said feedwater stream to produce said concentrated brine; (f) recirculating said concentrated brine in said evaporator; (g) adding a selected base to said concentrated brine to maintain a preselected pH level to enhance solubility of said silica, by adding said selected base to one or more of (i) said evaporator feedwater stream, or (ii) said liquid containing sump reservoir, or (iii) said concentrated brine recirculated from said sump reservoir to said plurality of heat transfer elements; (h) distributing said concentrated brine on a first surface of at least one of said plurality of heat transfer elements to generate a steam vapor; (i) compressing said steam vapor to produce a compressed steam vapor; (j) directing said compressed steam vapor to a second surface of at least one of said plurality of heat transfer elements to condense said compressed steam vapor and to form a distillate; (k) collecting said distillate; (l) discharging at least some of said concentrated brine as an evaporator blowdown stream; (m) introducing said distillate into a steam generator, to produce (i) high pressure steam, (ii) a boiler blowdown stream, said boiler blowdown stream comprising water and residual dissolved solids; (n) injecting said high pressure steam in injection wells to fluidize oil present in a selected geological formation, to produce an oil and water mixture; (o) gathering said oil/water mixture.