Sagdox operation in leaky bitumen reservoirs

Abstract

A method to operate a Steam Assisted Gravity Drainage with Oxygen (SAGDOX) process, in a leaky bitumen reservoir, wherein the process includes start-up, growth, decline and shut down phases. The start-up phase includes (1) Circulating steam in two horizontal (SAGD) wells, until communication is established between the two wells, (2) Injecting and optionally circulating steam in a SAGDOX oxygen injector well and vent gas well until communication is established, (3) Switching the wells to operate in a SAGD mode, with the upper well as a steam injector and the lower well as a fluid producer, creating a steam chamber, (4) Starting oxygen injection in the oxygen injector well, and (5) Opening at least one Produced Gas (PG) vent gas well, until steam injection is substantially limited to the upper well, oxygen injection has started and PG vent gas removal has started.

1 . A method to operate a Steam Assisted Gravity Drainage with Oxygen (SAGDOX) process, in a leaky bitumen reservoir, wherein said SAGDOX process comprises a start-up phase, growth phase, decline phase and shut down phase, said method comprising, at the start-up phase:
 (1) Circulating steam in two horizontal Steam Assisted Gravity Drainage (SAGD) wells, until communication is established between said two horizontal SAGD wells,   (2) Injecting and optionally circulating steam in a SAGDOX oxygen injector well and vent gas well until communication is established,   (3) Switching the horizontal wells to operate in a SAGD mode, with the upper well as a steam injector and the lower well as a fluid producer, creating a steam chamber,   (4) Starting oxygen injection in the SAGDOX oxygen injector well, with O 2 /steam (v/v) ratios of from about 0.05 to about 0.15, and   (5) Opening at least one Produced Gas (PG) vent gas well, until steam injection is substantially limited to the upper horizontal well, oxygen injection has started and PG vent gas removal has started.   
     
     
         2 . A method to operate a SAGDOX process, in a leaky bitumen reservoir, wherein said SAGDOX process comprises a start-up phase, growth phase, decline phase and shut down phase, in the growth phase of the process, preferably to increase/optimize bitumen productivity and preferably to achieve a WRR target for the process, said method comprising:
 (1) Adjusting oxygen/steam ratios (v/v),   (2) Adjusting energy injection rates (steam+oxygen) by controlling volumes and ratios,   (3) Adjusting vent gas well rates, and   (4) Adjusting production well sub-cool targets, until bitumen productivity peaks.   
     
     
         3 . A method to operate a SAGDOX process, in a leaky bitumen reservoir, wherein said SAGDOX process comprises a start-up phase, growth phase, decline phase and shut down phase, in the decline phase of the process, preferably resulting in at least one of improving energy efficiency, reducing costs, maximizing bitumen recovery and achieving a WRR target, comprising:
 (1) Increasing the oxygen/steam (v/v) ratio, preferably to a maximum of 1.0,   (2) Adjusting PG vent gas rates,   (3) Adjusting energy injection rates (steam+oxygen) by controlling volumes and ratios, and   (4) Adjusting production well sub-cool targets, preferably until economic limit for the SAGDOX process is substantially achieved.   
     
     
         4 . A method to operate a SAGDOX process in a leaky bitumen reservoir, wherein said SAGDOX process comprises a start-up phase, growth phase, decline phase and shut down phase in the shut-down phase of the process, preferably maximizing economic bitumen recovery, comprising:
 (1) Shutting off steam injection,   (2) Adjusting oxygen injection rates,   (3) Shutting off oxygen injection upon substantially achieving final economic limit, and   (4) Continuing residual bitumen production until the final economic limit is substantially achieved.   
     
     
         5 . The method of  claims 1 - 4 , wherein said SAGDOX process has system pressures selected from the group consisting of less than reservoir parting pressure, greater than native reservoir pressure, and substantially equal to native reservoir pressure. 
     
     
         6 . The method of  claims 1 - 4 , wherein the SAGDOX process pressure targets are replaced by Water Recycle Ratio (WRR) targets. 
     
     
         7 . The method of  claim 6 , wherein the WRR target is between 0.5 and 1.2. 
     
     
         8 . The method of  claim 7 , wherein the WRR target is between 0.8 and 1.2. 
     
     
         9 . The method of  claim 8 , wherein the WRR target is and between 0.9 and 1.2. 
     
     
         10 . The method of  claims 1 - 4 , wherein the SAGDOX process has a sub cool target between 5° C. and 30° C. 
     
     
         11 . The method of  claims 1 - 4 , wherein said bitumen is a liquid hydrocarbon with API<10 and viscosity>100,000 cp. 
     
     
         12 . The method of  claims 1 - 4 , wherein said leaky bitumen reservoir has a WRR outside the range 0.9 to 1.1, after 200 days or more of SAGDOX operation.