Heating a hydrocarbon reservoir

Abstract

A system and methods are provided for heating a hydrocarbon reservoir, wherein the reservoir includes a reduced oil saturation zone in proximity to a heavy oil zone. The method includes injecting an oxidizing gas into the reduced oil saturation zone and combusting hydrocarbons included within the reduced oil saturation zone. The method also includes determining a level of heating within the heavy oil zone that is conductively heated by combustion of the hydrocarbons within the reduced oil saturation zone, and producing hydrocarbons from the heavy oil zone once a desired level of heating has occurred.

What is claimed is: 
     
         1 . A method for heating a hydrocarbon reservoir, wherein the hydrocarbon reservoir comprises a reduced oil saturation zone in proximity to a heavy oil zone, the method comprising:
 injecting an oxidizing gas into the reduced oil saturation zone;   combusting hydrocarbons comprising the reduced oil saturation zone;   determining a level of heating within the heavy oil zone that is conductively heated by combustion of the hydrocarbons within the reduced oil saturation zone; and   producing hydrocarbons from the heavy oil zone once a desired level of heating has occurred.   
     
     
         2 . The method of  claim 1 , comprising allowing gases to accumulate within the reduced oil saturation zone. 
     
     
         3 . The method of  claim 1 , comprising producing gases from the reduced oil saturation zone. 
     
     
         4 . The method of  claim 3 , comprising using at least a portion of the gases produced for fuel. 
     
     
         5 . The method of  claim 3 , comprising using at least a portion of the gases in an enhanced oil recovery process. 
     
     
         6 . The method of  claim 3 , comprising storing at least a portion of the gases in another reservoir. 
     
     
         7 . The method of  claim 1 , wherein the reduced oil saturation zone comprises an oil reservoir that is at least partially depleted. 
     
     
         8 . The method of  claim 1 , wherein the reduced oil saturation zone is isolated from the heavy oil zone by at least one low permeability barrier to flow. 
     
     
         9 . The method of  claim 1 , wherein the oxidizing gas comprises air, enriched air, or oxygen, or any combinations thereof. 
     
     
         10 . The method of  claim 1 , comprising removing at least a portion of mobile water present in the reduced oil saturation zone. 
     
     
         11 . A system for heating a reservoir, comprising:
 a reservoir comprising a reduced oil saturation zone in proximity to a heavy oil zone, wherein the reduced oil saturation zone and the heavy oil zone are in thermal communication with one another;   an injection well, wherein the injection well is located within the reduced oil saturation zone, and wherein the injection well is configured to inject an oxidizing gas into the reduced oil saturation zone to sustain an in-situ combustion of hydrocarbons contained in the reduced oil saturation zone; and   a hydrocarbon recovery system, wherein the hydrocarbon recovery system is located within the heavy oil zone and is configured to produce mobilized fluids from the heavy oil zone.   
     
     
         12 . The system of  claim 11 , comprising a production well, wherein the production well is located within the reduced oil saturation zone and is configured to produce gas produced from the reduced oil saturation zone. 
     
     
         13 . The system of  claim 11 , wherein the reduced oil saturation zone is located above the heavy oil zone. 
     
     
         14 . The system of  claim 11 , wherein the reduced oil saturation zone is located within the heavy oil zone. 
     
     
         15 . The system of  claim 11 , wherein the reduced oil saturation zone is located below the heavy oil zone. 
     
     
         16 . The system of  claim 11 , wherein the reduced oil saturation zone is located between two vertically separated heavy oil zones. 
     
     
         17 . The system of  claim 11 , wherein the hydrocarbon recovery system comprises a production well at a first elevation and an injection well at a higher elevation. 
     
     
         18 . The system of  claim 17 , wherein the production well and the injection well are drilled either during the in-situ combustion, or after the in-situ combustion is complete. 
     
     
         19 . The system of  claim 17 , wherein the production well and the injection well are drilled before a combustion front from the in-situ combustion passes above a location of the production well and the injection well. 
     
     
         20 . The system of  claim 17 , wherein the production well and the injection well are drilled from offset locations such that a trajectory of the production well and a trajectory of the injection well do not pass through the reduced oil saturation zone. 
     
     
         21 . The system of  claim 11 , where the injection well comprises a vertical injection well, a deviated injection well, a slanted injection well, or a horizontal injection well, or any combinations thereof. 
     
     
         22 . The system of  claim 11 , wherein the reservoir comprises a reduced oil saturation zone in proximity to a plurality of heavy oil zones. 
     
     
         23 . The system of  claim 22 , comprising a hydrocarbon recovery system located within each of the plurality of heavy oil zones. 
     
     
         24 . The system of  claim 11 , comprising a layer of shale located between the reduced oil saturation zone and the heavy oil zone. 
     
     
         25 . The system of  claim 11 , wherein the reduced oil saturation zone comprises a high transmissibility zone. 
     
     
         26 . A method for recovering hydrocarbons from a hydrocarbon reservoir, wherein the hydrocarbon reservoir comprises a reduced oil saturation zone in thermal communication with a heavy oil zone, and wherein the method comprises:
 injecting an oxidizing agent into the reduced oil saturation zone;   combusting hydrocarbons contained in the reduced oil saturation zone in an in-situ combustion process, wherein conductive heat transferred from the in-situ combustion process heats hydrocarbons within the heavy oil zone; and   producing the hydrocarbons from the heavy oil zone once a desired level of heating has occurred within the heavy oil zone.   
     
     
         27 . The method of  claim 26 , comprising producing gas from the in-situ combustion process within the reduced oil saturation zone. 
     
     
         28 . The method of  claim 26 , wherein the oxidizing agent comprises air, enriched air, or oxygen, or any combinations thereof.