Low temperature monitoring system for subsurface barriers

• US 7,575,053 B2
• Filed: 04/21/2006
• Issued: 08/18/2009
• Est. Priority Date: 04/22/2005
• Status: Expired due to Fees

• Current Assignee: Shell Oil Company (Shell Plc)
• Original Assignee: Shell Oil Company (Shell Plc)
• Inventors: Vinegar, Harold J., McKinzie, Billy John II
• Primary Examiner(s): SUCHFIELD, GEORGE A
• Application Number:
  US11/409,563
• Publication Number:
  US 20070137857A1
• Time in Patent Office: 1,215 Days
• Field of Search: None
• US Class Current: 166/250.14
• CPC Class Codes: C07C 4/02 by cracking a single hydrocarbon or a mixture of individually defined hydrocarbons or a normally gaseous hydrocarbon fraction
• CPC Class Codes: C07C 9/04 Methane production by treatment of sewage C02F11/04; natural gas, synthetic natural gas C10L3/06
• CPC Class Codes: E21B 17/028 Electrical or electro-magnetic connections
• CPC Class Codes: E21B 36/001 Cooling arrangements
• CPC Class Codes: E21B 36/04 using electrical heaters
• CPC Class Codes: E21B 43/24 using heat, e.g. steam injection
• CPC Class Codes: E21B 43/243 Combustion in situ
• CPC Class Codes: Y10T 29/49179 by metal fusion bonding

Abstract

A system for monitoring temperature of a subsurface low temperature zone is described. The system includes a plurality of freeze wells configured to form the low temperature zone, one or more lasers, and a fiber optic cable coupled to at least one laser. A portion of the fiber optic cable is positioned in at least one freeze well. At least one laser is configured to transmit light pulses into a first end of the fiber optic cable. An analyzer is coupled to the fiber optic cable. The analyzer is configured to receive return signals from the light pulses.

Claims

1. A system for monitoring temperature of a subsurface low temperature zone, comprising:

a plurality of freeze wells configured to form the low temperature zone;

one or more lasers;

a fiber optic cable coupled to at least one laser, wherein portions of the fiber optic cable are positioned in a plurality of freeze wellbores, and wherein at least one laser is configured to transmit light pulses into a first end of the fiber optic cable; and

an analyzer coupled to the fiber optic cable, the analyzer configured to receive return signals from the light pulses.

2. The system of claim 1, further comprising:

a computer control system in communication with the analyzer; and

a formation refrigeration circulation system in communication with the computer control system, wherein the formation refrigeration circulation system is configured to supply refrigerant to the freeze wells and wherein the computer control system is configured to assess temperature profile data communicated from the analyzer.

3. The system of claim 2, wherein the computer control system is configured to automatically adjust the flow of refrigerant to the freeze wells.

4. The system of claim 1, wherein a portion of the fiber optic cable is positioned in at least one monitor well.

5. The system of claim 1, wherein the fiber optic cable comprises a fiber and a metal tube, wherein the fiber is positioned in the metal tube.

6. The system of claim 1, wherein a portion of the fiber optic cable adjacent to the low temperature zone is coiled.

7. The system of claim 1, wherein at least a portion of the fiber optic cable includes Bragg gratings.

8. The system of claim 1, wherein at least one laser is configured to transmit light pulses into a second end of the fiber optic cable.

9. The system of claim 1, wherein return signals from light transmitted into the second end of the fiber optic cable allows for compensation of signal attenuation.

10. The system of claim 1, wherein the fiber optic cable is one continuous fiber optic cable that extends through the plurality of wellbores.

11. A method of monitoring temperature of a low temperature subsurface barrier, comprising:

transmitting light through a fiber optic cable positioned in a plurality of wellbores used to form the subsurface low temperature barrier; and

analyzing one or more returned signals from the fiber optic cable with an analyzer to assess a temperature profile along the fiber optic cable.

12. The method of claim 11, wherein the fiber optic cable is positioned in at least one freeze well used to form the subsurface low temperature barrier.

13. The method of claim 11, wherein the fiber optic cable is positioned in at least one monitor wellbore.

14. The method of claim 11, wherein the analyzing comprises assessing the temperature profile in a freeze well used to form the subsurface low temperature barrier.

15. The method of claim 11, wherein the fiber optic cable is one continuous fiber optic cable that is positioned in the plurality of wellbores.

16. The method of claim 11, further comprising heating a subsurface formation at least partially surrounded by the barrier.

17. The method of claim 16, further comprising producing fluids from the subsurface formation, wherein the fluids comprise hydrocarbons.

18. The method of claim 16, further comprising producing transpiration fuel from at least of a portion of the hydrocarbons.

19. A method to locate a breach in a frozen barrier, the frozen barrier comprising a plurality of wellbores containing fiber optic cables and through which the frozen barrier is created by circulation of a refrigerant, the method comprising:

discontinuing circulation of the refrigerant;

assessing temperature profiles of the wellbores based on information obtained from the fiber optic cables after circulation has ceased; and

determining the location of a breach by analysis of the temperature profiles.

20. The method of claim 19, wherein assessing comprises using a computer controller system to assess the temperature profile in a freeze well used to form the subsurface low temperature barrier.

21. The method of claim 19, further comprising reporting the temperature profile.

22. The method of claim 19, further comprising automatically discontinuing circulation of the refrigerant.

23. The method of claim 19, further comprising assessing temperature profiles of the wellbores based on information obtained from the fiber optic cables after circulation has ceased.

24. The method of claim 19, further comprising reporting the location of the breach.