Patent ID: 7077201

Claim:
A method of producing steam for downhole injection in the recovery of heavy oil, said method comprising: (a) providing an oil/water mixture gathered from an oil/water collection well, (b) substantially separating oil from said oil/water mixture to provide an oil product and an oil containing produced water; (c) de-oiling said oil containing produced water to at least partially provide an evaporator feedwater, said evaporator feedwater comprising water, dissolved solutes, and dissolved gases, said dissolved solutes comprising silica (d) heating said evaporator feedwater to remove at least some of said dissolved gases; (e) injecting said evaporator feedwater into an evaporator, and concentrating said evaporator feedwater to produce a concentrated heated brine, said evaporator having a plurality of heat transfer surfaces; (f) maintaining the pH of said concentrated heated brine as necessary to maintain solubility of silica therein at a selected concentration factor; (g) distributing said brine on a first surface of at least one of said plurality of heat transfer surfaces to generate a steam vapor; (h) discharging at least some of said brine as an evaporator blowdown stream; (i) slightly 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 surfaces to condense said compressed steam vapor and to form a distillate; (k) collecting said distillate; (l) introducing said distillate into a boiler, to produce (i) steam, (ii) a boiler blowdown stream, said boiler blowdown stream comprising water and residual dissolved solids. (iii) adding said boiler blowdown stream to said evaporator feedwater prior to the step of heating said evaporator feedwater; (m) injecting said steam in injection wells to fluidize oil present in a selected geological formation, to produce an oil and water mixture for collection at a production well; (n) gathering said oil and water mixture.