Sagd water treatment system and method

Abstract

A method and system for treating a water stream which contains Fouling Organics, where the water stream is recovered from an underground hydrocarbon-containing formation during SAGD oil recovery operations conducted on said formation. The method comprises injecting an oxidizing agent, preferably air, into the water stream when first recovered from the underground formation, and using a porous membrane to separate oxidized Fouling Organics and/or filter separable compounds formed due to injection of the oxidizing agent into the water stream, prior to transferring the water stream to a boiler for re-heating the water stream and turning same to steam for re-injection into said formation.

1 . A method for treating boiler feed water containing Fouling Organics in a SAGD oil recovery process, wherein said water containing Fouling Organics is derived from SAGD oil recovery methods performed on an underground hydrocarbon-containing formation, comprising the steps of:
 (i) obtaining water from an underground hydrocarbon-containing formation during SAGD oil recovery methods performed on said underground formation, wherein said water contains Fouling Organics, said water having been passed through an oil-water separator as an initial means of removing a portion of oil from within said water, said water continuing to have Fouling Organics remaining therein;   (ii) injecting an oxidizing agent into said water;   (iii) filtering said Fouling Organics from said water to separate said Fouling Organics and thereby reduce the concentration of Fouling Organics in said water;   (iv) subsequently supplying said water having a reduced concentration of Fouling Organics therein to a boiler and turning said water into steam; and   (v) injecting said water, now in the form of steam, into said hydrocarbon-containing formation during said SAGD oil recovery operation.   
     
     
         2 . The method for treating said boiler feedwater containing Fouling Organics in said SAGD oil recovery process of  claim 1 , wherein said water is from a produced water stream. 
     
     
         3 . The method for treating said boiler feedwater containing Fouling Organics in said SAGD oil recovery process of  claim 1 , wherein said water is from a recycled boiler water stream. 
     
     
         4 . The method for treating said boiler feedwater containing Fouling Organics in said SAGD oil recovery process of  claim 1 , wherein said water is a combination of water from a produced water stream and a recycled boiler water stream. 
     
     
         5 . The method for treating said boiler feedwater containing Fouling Organics in said SAGD oil recovery process of  claim 1 , wherein said oxidizing agent chemically reacts with said Fouling Organics present in said water to:
 (a) change the surface structure of said Fouling Organics to have less affinity to a membrane surface so as to thereby result in less fouling of said membrane surface;   (b) cause said Fouling Organics to agglomerate or polymerize to an increased molecular size and/or molecular weight so as to thereby permit being filtered out of said water;   (c) form a compound of lower solubility in said water than said Fouling Organics;   (d) cause said Fouling Organics to form flocs or chelate with other inorganic impurities in said water; or   (e) change the surface functional groups to be amphipathic so as to cause foaming.   
     
     
         6 . The method for treating boiler feedwater containing Fouling Organics in said SAGD oil recovery process of  claim 5 , wherein said oxidizing agent is an oxidizing agent selected from the group of oxidizing agents consisting of oxygen, air, ozone, alkali permanganate, chlorine dioxide, and hydrogen peroxide. 
     
     
         7 . The method of  claim 6 , wherein said oxidizing agent is oxygen contained in air. 
     
     
         8 . The method for treating said boiler feedwater containing Fouling Organics in said SAGD oil recovery process of  claim 7 , wherein said step of filtering comprises:
 passing said water, after said air is provided to said water and prior to providing said water to said boiler, through a filter or membrane to filter Fouling Organics therefrom.   
     
     
         9 . The method of  claim 8 , wherein said filter is a nano-filter. 
     
     
         10 . The method of  claim 8 , wherein said water is passed through a semi-porous membrane. 
     
     
         11 . The method for treating said boiler feedwater containing Fouling Organics as claimed in  claim 6 , wherein subsequent to said oxidizing agent injection step said water is subject to deoxidation before being passed into said boiler. 
     
     
         12 . The method of  claim 11 , wherein said oxidizing agent is air or oxygen, and subsequent to said oxidizing agent injection step said water is subject to both deaeration and deoxygenation before being passed into said boiler. 
     
     
         13 . The method for treating said boiler feedwater containing Fouling Organics as claimed in  claim 6 , comprising the step of adding chemical oxygen scavengers to remove oxygen from said water. 
     
     
         14 . A method for treating boiler feedwater containing Fouling Organics in a SAGD oil recovery process, wherein said water containing oil and Fouling Organics is recovered during SAGD oil recovery methods performed on an underground hydrocarbon-containing formation, and said Fouling Organics are at least partly removed from said water so as to reduce the concentration of said Fouling Organics in said water prior to heating of said water and re-injection of said water in the form of steam into said underground formation, comprising the steps of:
 obtaining water from an underground hydrocarbon-containing formation during SAGD oil recovery methods performed on said underground formation, wherein said water contains Fouling Organics, said water having been passed through an oil-water separator as an initial means of removing at least a portion of oil from within said water, said water continuing to have Fouling Organics remaining therein;   (i) injecting air into said water to oxidize said Fouling Organics present in such water;   (ii) filtering said water by passing said water through a membrane to separate said Fouling Organics from said water and thereby reduce the concentration of Fouling Organics in said water;   (iii) deaerating and/or deoxygenating said water;   (iv) subsequently supplying said filtered water to a boiler and using said boiler to turn said water into steam; and   (v) injecting said water, now in the form of steam, into said hydrocarbon-containing formation during said SAGD oil recovery operation.   
     
     
         15 . The method for treating said boiler feedwater containing Fouling Organics in said SAGD oil recovery process of  claim 14 , wherein said water is from a produced water stream. 
     
     
         16 . The method for treating said boiler feedwater containing Fouling Organics in said SAGD oil recovery process of  claim 14 , wherein said water is from a recycled boiler water stream. 
     
     
         17 . The method for treating said boiler feedwater containing Fouling Organics in said SAGD oil recovery process of  claim 14 , wherein said water is a combination of water from a produced water stream and a recycled boiler water stream. 
     
     
         18 . A system for treating water containing Fouling Organics in a SAGD oil recovery process, wherein said water is recovered from within an underground hydrocarbon-containing formation during SAGD oil recovery methods performed on said underground formation, and re-injected as steam into said formation for heating hydrocarbons in said formation, comprising:
 (i) oxidizing agent injection means for injecting an oxidizing agent into a water stream obtained from said hydrocarbon-containing formation, which water stream contains Fouling Organics;   (ii) filter means for separating oxidized Fouling Organics and/or filter-separable compounds formed as a result of reaction between said oxidizing agent and said Fouling Organics, from said water stream;   (iii) boiler means for heating said water stream so as to form steam; and   (iv) injection means for re-injecting said steam into said hydrocarbon-containing formation.   
     
     
         19 . The system as claimed in  claim 18 , wherein said oxidizing agent injection means comprises air injection means so as to permit injection of air into said water stream prior to said water stream passing through said filter means. 
     
     
         20 . The system as claimed in  claim 18 , wherein said filter means comprises at least one semi-permeable membrane adapted to separate oxidized Fouling Organics and/or filter-separable compounds formed as a result of reaction between said oxidizing agent and said Fouling Organics, from said water stream. 
     
     
         21 . The system as claimed in  claim 18 , wherein said water stream is a produced water stream. 
     
     
         22 . The system as claimed in  claim 18 , further comprising recycle means for said water stream exiting said boiler which has not been turned to steam, to permit same to be re-exposed to said oxidizing agent. 
     
     
         23 . The system as claimed in  claim 18 , wherein said oxidizing agent injection means and filter means are located downstream from a recycle means, said recycle means for a recycled boiler water stream exiting said boiler, whereby said recycled boiler water stream is separately injected with said oxidizing agent and filtered by said filter means to be subsequently combined with a produced water stream prior to entering said boiler means. 
     
     
         24 . The system as claimed in  18 , further comprising de-oiling means in said water stream, positioned in said water stream at a location upstream from said filter means. 
     
     
         25 . The system as claimed in  claim 24 , wherein said de-oiling means is located upstream from said oxidizing agent injection means and said filter means. 
     
     
         26 . The system as claimed in  claim 25 , wherein said de-oiling means comprises weir-separator means for separating hydrocarbons from said water stream. 
     
     
         27 . The system as claimed in  claim 18 , said system further comprising deoxidizing means for removing oxidizing agent from said water subsequent to injection of said oxidizing agent, and prior to said water being provided to said boiler. 
     
     
         28 . The system as claimed in  claim 27 , wherein said oxidizing agent is air or oxygen and said dexodizing means is deaeration and/or deoygenation means for removing oxygen from said water subsequent to injection of said air or oxygen, and prior to said water being provided to said boiler.