In situ combustion process with reduced CO

1. A method of recovering a hydrocarbon mixture from a subterranean formation comprising:

(i) injecting an oxygen-rich gas into said formation;

(ii) combusting said oxygen-rich gas in said formation thereby heating and reducing the viscosity of said hydrocarbon mixture and generating CO 2 -rich gas;

(iii) recovering said heated hydrocarbon mixture and deasphalting said recovered hydrocarbon mixture in a deasphlating unit to produce deasphalted hydrocarbon and asphaltenes;

(iv) combusting said asphaltenes produced in said deasphalting unit in an oxycombustion process to produce steam, power and CO 2 -rich gas; and

(v) capturing at least a portion of CO 2 from said CO 2 -rich gas.

2. A method as claimed in claim 1 , comprising the further step of:

(via) using said captured CO 2 in a method of recovering a hydrocarbon mixture.

3. A method as claimed in claim 2 , wherein said captured CO 2 is used to form oxygen-rich gas for injection in step (i).

4. A method as claimed in claim 1 , comprising the further step of:

(vib) storing at least a portion of CO 2 from said CO 2 -rich gas in a formation.

5. A method as claimed in claim 1 , wherein said oxygen-rich gas comprises at least 25% by volume oxygen and/or CO 2 .

6. A method as claimed in claim 1 , wherein said oxygen-rich gas comprises CO 2 .

7. A method as claimed in claim 1 , wherein said oxygen-rich gas comprises at least 30% by volume oxygen.

8. A method as claimed in claim 1 , wherein said oxygen-rich gas comprises at least 5% by volume CO 2 .

9. A method as claimed in claim 1 , wherein said formation is heated, e.g. by steam injection, prior to injection of said oxygen-rich gas.

10. A method as claimed in claim 1 , comprising

(i) injecting an oxygen-rich gas into said formation via a vertical injection well;

(ii) combusting said oxygen-rich gas in said formation thereby heating and reducing the viscosity of said hydrocarbon mixture and generating CO 2 -rich gas;

(iiia) recovering said CO 2 -rich gas via a vertical vent well;

(iiib) recovering said heated hydrocarbon mixture via a substantially horizontal production well and deasphalting said recovered hydrocarbon mixture in a deasphalting unit to produce deasphalted hydrocarbon and asphaltenes;

(iv) combusting said asphaltenes produced in said deasphalting unit in an oxycombustion process to produce steam, power and CO 2 -rich gas; and

(v) capturing at least a portion of CO 2 from said CO 2 -rich gas.

11. A method as claimed in claim 1 , wherein said CO 2 -rich gas comprises at least 70% by volume CO 2 .

12. A method as claimed in claim 1 , wherein said recovered hydrocarbon mixture has an API of 10-17°.

13. A method as claimed in claim 1 , wherein said deasphalted hydrocarbon mixture has an API in the range 16-25°.

14. A method of recovering a hydrocarbon mixture from a subterranean formation, comprising the steps of:

combusting an oxygen and CO 2 mixture in said formation thereby heating and reducing the viscosity of said hydrocarbon mixture and generating a CO 2 -rich gas;

recovering said heated hydrocarbon mixture;

deasphalting said recovered hydrocarbon mixture in a deasphalting unit to produce desasphalted hydrocarbon and asphaltenes;

combusting said asphaltenes produced in said deasphalting unit in an oxycombustion process to produce steam, power and CO 2 -rich gas; and

capturing at least a portion of CO 2 from said CO 2 -rich gas.

15. A method as claimed in claim 14 , wherein at least a portion of CO 2 from said CO 2 -rich gas is used in a method of recovering a hydrocarbon mixture.

16. A method as claimed in claim 14 , wherein at least a portion of CO 2 from said CO 2 -rich gas is stored in a formation.

17. A well arrangement comprising:

(a) a vertical injection well having an inlet for injecting an oxygen-rich gas into a formation;

(b) a substantially horizontal production well for recovering a hydrocarbon mixture; and

(c) a vertical vent well having an outlet for recovering CO 2 rich gas;

wherein said outlet of said vertical vent well is connected to a CO 2 purifier.

18. A well arrangement as claimed in claim 17 , wherein said CO 2 purifier is connected to said inlet of said injection well.

19. A well arrangement as claimed in claim 17 , wherein said CO 2 purifier is connected to a means for transporting CO 2 into a formation for storage.