Methods for treatment and use of produced water

Abstract

Produced water is treated by raising the pH to a level that significantly increases silica solubility and breaks emulsions. So treated water is then de-oiled, filtered, and subjected to ion exchange chromatography to reduce water hardness prior to feeding into a steam generator to form an intermediate quality steam. If desired, the intermediate quality steam is directly used in SAGD, or separated into a high quality steam and condensate, which is further treated to obtain additional water that can then be used in the steam generator.

What is claimed is: 
     
         1 . A method of processing produced water, comprising:
 providing a quantity of produced water, and de-oiling and removing solids from the produced water to thereby form treated water;   removing divalent cations from the treated water using an ion exchange resin to thereby produce softened water;   increasing alkalinity of the softened water to thereby form alkalinized water, and forming an intermediate quality steam product from the alkalinized water; and   using at least a portion of the intermediate quality steam product for injection into a formation.   
     
     
         2 . The method of  claim 1  wherein the step of using at least a portion of the intermediate quality steam product comprises separation of the intermediate quality steam product into a condensate and a high quality steam product, and a further step of injection of the high quality product into the formation. 
     
     
         3 . The method of  claim 2  further comprising a step of processing the condensate to obtain additional water, and using the additional water in the step of forming the intermediate quality steam product. 
     
     
         4 . The method of  claim 3  wherein the step of processing the condensate comprises feeding the condensate into a brine concentrator. 
     
     
         5 . The method of  claim 1  wherein the step of using at least a portion of the intermediate quality steam product comprises using substantially all of the intermediate quality steam product for injection into the formation. 
     
     
         6 . The method of  claim 1  wherein the step of forming the intermediate quality steam is performed using a once-through steam generator. 
     
     
         7 . The method of  claim 1  wherein the alkalinized water has a pH of at least pH 10. 
     
     
         8 . The method of  claim 1  wherein the intermediate quality steam product comprises between 10 and 30% condensate. 
     
     
         9 . The method of  claim 1  wherein the steps of increasing alkalinity, removing divalent cations, and forming the intermediate quality steam product are performed without a step of removing silicate from the produced water, the treated water, the softened water, and the alkalinized water, respectively. 
     
     
         10 . The method of  claim 1  further comprising a step of adding previously isolated silica to the produced water, the treated water, the softened water, or the alkalinized water. 
     
     
         11 . The method of  claim 1  wherein the ion exchange resin comprises a weak acid cation ion exchange resin. 
     
     
         12 . A method of processing produced water, comprising:
 providing produced water comprising silica, and de-oiling and removing solids from the produced water;   removing divalent cations from the produced water using an ion exchange resin; and   adding a base to the produced water to thereby form alkalinized water, wherein the base is added in an amount that increases solubility of the silica in the alkalinized water at least 25% as compared to the produced water.   
     
     
         13 . The method of  claim 12  wherein the base is an alkaline metal hydroxide or an alkaline earth metal hydroxide. 
     
     
         14 . The method of  claim 12  wherein the base is added in an amount to achieve a pH of at least 10 in the alkalinized water. 
     
     
         15 . The method of  claim 12  wherein the step of de-oiling comprises a step of chemically breaking an emulsion in the produced water. 
     
     
         16 . The method of  claim 12  further comprising a step of forming an intermediate quality steam product from the alkalinized water, and still further comprising a step of using at least a portion of the intermediate quality steam product for injection into a formation. 
     
     
         17 . A method of processing produced water, comprising:
 providing produced water comprising silica;   chemically breaking an emulsion in the produced water, and removing oil and precipitate from the produced water;   removing divalent cations from the produced water using an ion exchange resin;   adding a base to the produced water to thereby form alkalinized water, and forming an intermediate quality steam product from the alkalinized water without a step of removing silica from the produced water.   
     
     
         18 . The method of  claim 17  wherein the base is added in an amount to achieve a pH of at least 10 in the alkalinized water. 
     
     
         19 . The method of  claim 17  further comprising a step of adding previously isolated silica to the produced water or the alkalinized water. 
     
     
         20 . The method of  claim 17  further comprising a step of using at least a portion of the intermediate quality steam product for injection into a formation.