Direct steam generation co2 output control

Abstract

Methods and systems generate steam and carbon dioxide mixtures suitable for injection to assist in recovering hydrocarbons from oil sands based on concentration of the carbon dioxide in the mixtures as influenced by temperature of water introduced into a direct steam generator. Increasing temperature of the water to above 200° C. before introduction into the direct steam generator may utilize heat from an electrical power generation unit. Enthalpy of this preheated water impacts amount of fuel needed to burn in the direct steam generator and hence the concentration of the carbon dioxide, which may be below 11% by mass percent of the steam.

1 . A method of generating a mixture of steam and carbon dioxide, comprising:
 supplying fuel and oxidant into a direct steam generator;   heating water to above 200° C. for introducing in liquid phase into the direct steam generator; and   combusting the fuel and oxidant in the direct steam generator as the water that is preheated is introduced to produce the mixture that includes the steam and combustion products and that has a carbon dioxide level in mass percent of the steam below 11 percent.   
     
     
         2 . The method according to  claim 1 , wherein the heating of the water includes heat exchange with heat from an electrical power generation unit. 
     
     
         3 . The method according to  claim 1 , wherein the heating of the water includes heat exchange with fluids recovered from a hydrocarbon production well and then with heat from an electrical power generation unit. 
     
     
         4 . The method according to  claim 1 , wherein a portion of the water is introduced into the direct steam generator at a temperature below 200° C. in an area of the direct steam generator upstream from where the water above 200° C. is introduced. 
     
     
         5 . The method according to  claim 1 , wherein the water is above 250° C. and at a pressure above 6000 kilopascals when introduced into the direct steam generator. 
     
     
         6 . The method according to  claim 1 , wherein the water is supplied by recycling condensate of the steam recovered following injection of the mixture into a formation. 
     
     
         7 . The method according to  claim 1 , further comprising injecting the mixture into a formation to assist recovery of hydrocarbons. 
     
     
         8 . The method according to  claim 1 , wherein the fuel includes hydrocarbons and the carbon dioxide level in mass percent of steam is below 10 percent. 
     
     
         9 . The method according to  claim 1 , wherein the fuel is natural gas and the oxidant is oxygen separated from air. 
     
     
         10 . The method according to  claim 1 , wherein the water is introduced into the direct steam generator at more than 30° C. below a temperature of the mixture output. 
     
     
         11 . The method according to  claim 1 , wherein the water is between 250° C. and 280° C. when introduced into the direct steam generator and the mixture is output from the direct steam generator above 280° C. and at least 6000 kilopascals. 
     
     
         12 . A system for generating a mixture of steam and carbon dioxide, comprising:
 a device for heating water and configured for outputting the water in liquid phase at a temperature above 200° C.; and   a direct steam generator coupled in fluid communication with an output of the device for heating the water and configured to combust fuel and oxidant as the water from the output of the device is introduced into the direct steam generator to produce the mixture that includes the steam and combustion products and has a carbon dioxide level in mass percent of steam below 11 percent.   
     
     
         13 . The system according to  claim 12 , wherein the device for heating the water includes a heat exchanger to transfer heat from an electrical power generation unit. 
     
     
         14 . The system according to  claim 12 , wherein the device for heating the water includes a first heat exchanger for transferring heat from fluids recovered from a hydrocarbon production well and a second heat exchanger for transferring heat from an electrical power generation unit. 
     
     
         15 . The system according to  claim 12 , further comprising an injection well in fluid communication with the mixture output from the direct steam generator. 
     
     
         16 . The system according to  claim 12 , wherein the device for heating the water is configured to heat the water to between 250° C. and 300° C. 
     
     
         17 . The system according to  claim 12 , wherein the direct steam generator is operable to provide the carbon dioxide level in mass percent of steam below 10 percent and combust the fuel that includes hydrocarbons. 
     
     
         18 . The system according to  claim 12 , wherein the direct steam generator is coupled to receive a portion of the water at a temperature below 200° C. in an area of the direct steam generator upstream from where the water above 200° C. is introduced. 
     
     
         19 . A method of generating a mixture of steam and carbon dioxide, comprising:
 combusting fuel and oxidant in a direct steam generator as water that is heated to above 200° C. and in liquid phase is introduced into the direct steam generator to produce the mixture that includes the steam and combustion products and has a carbon dioxide level in mass percent of steam below 11 percent;   introducing the mixture into a formation; and   recovering a hydrocarbon emulsion containing a condensate of the steam that is recycled for resupplying of the water heated before entering the direct steam generator.   
     
     
         20 . The method according to  claim 19 , wherein the introducing of the mixture into the formation is through a horizontal injection well above a horizontal production well through which the emulsion is recovered in a steam assisted gravity drainage process.