Patent EA-000250-B1 (EA)
Title: Flameless combustor
Inventor: KARANIKAS JOHN MICHAEL
IPC: E21B36/02
Filed: 1996-12-17
Abstract: 1. A flameless combustor for combustion of a fuel and oxidant mixture, the combustor comprising: a combustion chamber (14) in communication with an inlet and with a combustion product outlet (10); and a catalyst surface (20) within the combustion chamber (14) characterized in that the combustor further comprises a mixed fuel and oxidant supply (22) in communication with the inlet; and that the catalyst surface (20) is effective to cause oxidization of an amount of fuel wherein the oxidization of the amount of fuel does not result in a temperature above an uncatalyzed autoignition temperature of the fuel and oxidant mixture. 2. The combustor of Claim 1 wherein the catalyst surface (20) comprises a component selected from the group consisting of noble metals, semi-precious metals, transition metal oxides and mixtures thereof. 3. The combustor of Claim 1 wherein the catalyst surface (20) comprises palladium. 4. The combustor of Claim 1 wherein the catalyst surface (20) comprises platinum. 5. The combustor of Claim 1 further comprising a preheat section (22) wherein in the preheat section (22) heat can be exchanged between the fuel and oxidant mixture and the combustion products. 6. The combustor of any preceding Claim wherein the combustor is designed for heating a subterranean formation by combustion of a fuel and oxidant mixture; the combustion chamber (14) is defined by at least one combustion tubular (4, 10) which is located in a wellbore within the formation to be heated; and the combustor comprises a combustion gas outlet (10) within the wellbore for allowing combustion products to flow to the surface. 7. The combustor of Claim 6 wherein the catalyst surface area (20) is distributed within the combustion chamber (14) to result in an essentially constant temperature within the combustion chamber (14). 8. The combustor of Claim 6 wherein the combustion chamber (14) is defined by one or more tubular pipes (4, 10) placed within the wellbore. 9. The combustor of Claim 6 wherein the combustion gas outlet is an annular space (22) surrounding the combustion tubular (4). 10. The combustor of Claim 6 wherein the combustion gas outlet is a tubular (10) within the combustion chamber (14). 11. The combustor of Claim 6 wherein the combustion chamber (14) comprises an annular volume between a tubular (10) and a casing (4). 12. The combustor of Claim 11 wherein the tubular (10) is a conduit for return of combustion products to a wellhead. 13. The combustor of Claim 6 wherein the tubular (10) is a conduit containing another portion of the combustion chamber (14). 14. The combustor of any preceding Claim wherein the catalyst surface (20) is provided by a catalyst coating which covers at least part of the inner and/or outer surface of a tubular (10) within the combustion chamber (14). 15. The combustor of any preceding Claim wherein the inlet is located at one end of the combustion chamber (14) and the outlet is located at the other end of the combustion chamber. 16. A method of heating a subterranean formation by flameless combustion, the method comprising: installing a combustion tubular (10) which defines a downhole combustion chamber (14) in a wellbore (3) within the formation (1) to be heated and inducing fuel and oxidant to flow along a catalyst surface (20) within the combustion chamber (14); characterized in that the method further comprises feeding a fuel and oxidant mixture to the chamber (14) via an inlet; wherein the catalyst surface (20) is effective to cause oxidization of an amount of fuel at such a rate that the average temperature in the combustion chamber (14) remains below the uncatalyzed autoignition temperature of the fuel and oxidant mixture; and allowing combustion products to flow to the surface via a combustion product outlet conduit (10) within the wellbore (3). 17. The method of Claim 16 wherein the combustion chamber (14) is defined by a lower portion of a well casing (4) and a plug (23) near the bottom of the well casing (4) and the catalyst surface (20) is provided by a catalyst coating on the inner and/or outer surface of a tubular (10) which is co-axially suspended within the well casing (4) such that an axial spacing is maintained between a lower end of the suspended tubular (10) and the plug (23). 18. The method of Claim 17 wherein the suspended tubular (10) is used as a mixed fuel and air inlet conduit and the annular space (22) between the tubular (10) and the well casing (4) is used as a combustion product outlet conduit or vice versa. 19. The method of Claim 16, 17 or 18 wherein the method is used for heating a subterranean oil shale formation (1) of low permeability.