US 6,733,636 B1Granted

Water treatment method for heavy oil production

AssigneeIonics, Incorporated

InventorWilliam F. Heins

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Abstract

A method of treating produced water from heavy oil production to provide feedwater for the production of high quality steam. A produced water from heavy oil recovery operations is initially treated by first removing oil and grease to a desired level, preferably to about twenty parts per million, or less. The pH is then adjusted, normally downward and by acid addition, to release at least some carbonate alkalinity as free carbon dioxide. Preferably, all non-hydroxide alkalinity is removed, or substantially so, by introducing the feedwater into a decarbonator. In some cases, the pH may be raised (without, or subsequent to decarbonation, depending upon water chemistry) preferably by caustic addition, to maintain silica solubility in the feedwater. Next the feedwater is introduced into an evaporator, and the feedwater is evaporated to a pre-selected concentration factor to produce (1) a distillate having a small amount of residual hardness therein, and (2) a concentrate containing residual solids (dissolved solids and in some cases, suspended solids). The distillate is then cooled, and is subsequently introduced into a hardness removal step, preferably an electrodeionization (EDI) treatment unit, to remove the residual hardness from the distillate. Finally, the substantially hardness free treated water stream is sent to packaged boilers, for production of high quality steam. The hardness containing stream from EDI is recycled to the evaporator feed, for further treatment.

Claims27

Dependent claims

A method of producing steam for downhole injection in the recovery of heavy oil, said method comprising:

(a) providing an oil and water mixture gathered from an oil and water collection well;
(b) substantially separating oil from said oil and water mixture to produce (i) an oil product, and (ii) produced water having residual oil therein;
(c) de-oiling said 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 heated evaporator feedwater into a circulating concentrated brine in an evaporator;
said evaporator having a plurality of heat transfer surfaces;
(f) raising the pH of said concentrated brine to maintain solubility of silica in said concentrated brine;
(g) distributing said concentrated brine on a first surface of at least one of said plurality of heat transfer surfaces to generate a steam vapor and further concentrating said circulating concentrated brine;
(h) discharging at least some of said concentrated brine as an evaporator blowdown stream;
(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 surfaces to condense said compressed steam vapor to form a distillate having residual solutes therein;
(k) collecting said distillate;
(l) removing said residual solutes from said distillate via electrodeionization treatment or via ion exchange treatment to produce (a) a substantially solute free distillate stream and (b) a solute containing reject stream;
(m) introducing said distillate stream 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.

14 more elements

A method of producing steam for downhole injection in the recovery of heavy oil, said method comprising:

(a) providing an oil and water mixture gathered from an oil and water collection well;
(b) substantially separating oil from said oil and water mixture to provide (i) an oil product, and (ii) produced water having residual oil therein;
(c) de-oiling said 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 a concentrated brine in an evaporator;
said evaporator having a plurality of heat transfer surfaces;
(f) raising the pH of said concentrated brine as necessary to maintain solubility of silica in said concentrated brine;
(g) distributing said concentrated 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 concentrated brine as an evaporator blowdown stream;
(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 surfaces to condense said compressed steam vapor to form a distillate having residual solutes therein;
(k) collecting said distillate;
(i) removing said residual solutes from said distillate via electrodeionization treatment or via ion exchange treatment to produce (a) a substantially solute free distillate stream and (b) a solute containing reject stream;
(m) introducing said distillate stream 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;
(n) injecting said steam in an injection well to produce an oil and water mixture;
(o) gathering said oil and water mixture.

16 more elements

Dependencies are inferred from the claim text.