Direct steam generation of boiler blowdown

Abstract

Systems and methods generate steam from produced water by passing the produced water through first and second steam generators coupled together. The first steam generator produces wet steam in which a liquid effluent with impurities of the produced water passes to the second steam generator. The second steam generator combusts fuel and oxidant in direct contact with the liquid effluent. The first and second steam generators limit fouling and waste while providing a combined steam output that may include combustion products from only the second steam generator.

1 . A method of generating steam, comprising:
 injecting water into an initial steam generator to produce steam and a liquid effluent containing a remainder of the water with impurities; and   injecting the liquid effluent into a direct steam generator to vaporize at least part of the liquid effluent upon contact with combustion products such that a resulting gas phase including additional steam and carbon dioxide is output separate from a non-gas phase waste stream.   
     
     
         2 . The method of  claim 1 , wherein the liquid effluent vaporizes in the direct steam generator leaving the waste stream formed of solid particles. 
     
     
         3 . The method of  claim 1 , wherein the waste stream includes liquid brine formed by incomplete vaporization of the liquid effluent supplied in excess of a saturation amount for the direct steam generator. 
     
     
         4 . The method of  claim 1 , wherein the impurities include combustible compounds combusted by excess oxidant supplied to the direct steam generator. 
     
     
         5 . The method of  claim 1 , wherein the steam from both the initial and direct steam generators is injected into a well for a steam assisted gravity drainage operation. 
     
     
         6 . The method of  claim 1 , wherein the steam from the direct steam generator is superheated. 
     
     
         7 . The method of  claim 1 , wherein the steam from both the initial and direct steam generators is injected into a well and the steam from the direct steam generator is superheated to a temperature that prevents condensation prior to injection into the well. 
     
     
         8 . The method of  claim 1 , wherein the steam from the initial steam generator and the gas phase from the direct steam generator are combined into a mixture that is injected into a well and includes steam with less than 5 percent carbon dioxide by weight. 
     
     
         9 . The method of  claim 1 , wherein the steam from the initial steam generator and the gas phase from the direct steam generator are combined into a mixture that is injected into a well and includes steam with between 2 and 4 percent carbon dioxide by weight. 
     
     
         10 . The method of  claim 1 , wherein the initial steam generator includes a once through steam generator that produces a steam quality between 70 percent and 85 percent with the remainder of the water going to the liquid effluent. 
     
     
         11 . A system for generating steam, comprising:
 an initial steam generator coupled to receive water and having a first output for steam and a second output for liquid effluent containing a remainder of the water with impurities; and   a direct steam generator coupled to receive the liquid effluent for at least partial vaporization upon contact with combustion products and having a third output for a resulting gas phase including additional steam and carbon dioxide and a fourth output for a non-gas phase waste stream.   
     
     
         12 . The system of  claim 11 , wherein the direct steam generator vaporizes the liquid effluent leaving the waste stream formed of solid particles. 
     
     
         13 . The system of  claim 11 , wherein the direct steam generator produces the waste stream of liquid brine formed by incomplete vaporization of the liquid effluent. 
     
     
         14 . The system of  claim 11 , wherein the impurities include combustible compounds combusted by excess oxidant supplied to the direct steam generator. 
     
     
         15 . The system of  claim 11 , further comprising a well for a steam assisted gravity drainage operation that is coupled to both the initial and direct steam generators for steam injection. 
     
     
         16 . The system of  claim 11 , wherein the direct steam generator produces the steam that is superheated. 
     
     
         17 . The system of  claim 11 , further comprising a well coupled to the first and third outputs such that a mixture injected into the well includes steam with less than 5 percent carbon dioxide by weight. 
     
     
         18 . The system of  claim 11 , further comprising a well coupled to the first and third outputs such that a mixture injected into the well includes steam with 2 to 4 percent carbon dioxide by weight. 
     
     
         19 . The system of  claim 11 , wherein the initial steam generator includes a once through steam generator that produces a steam quality between 70 percent and 85 percent with the remainder of the water going to the liquid effluent. 
     
     
         20 . A method of generating steam, comprising:
 recovering production fluid from a reservoir;   separating the production fluid into an oil stream and a water stream;   generating steam from the water stream by partial vaporization of the water stream while isolated from fluid communication with combustion products and then further vaporization of the water stream while in fluid communication with combustion products; and   injecting the steam into the reservoir for a steam assisted gravity drainage operation.