Detection of leaks from a pipeline using a distributed temperature sensor

1. A method of detecting leaks from a pipeline, comprising:

operating a distributed temperature sensing (DTS) system to obtain temperature profiles from a sensing element deployed along a length of a pipeline that is carrying a fluid, wherein the temperature profiles are measures of temperature at sample distance points along the sensing element;

spatially filtering the temperature profiles to generate filtered temperature profiles that are limited to a set of spatial frequencies that corresponds to an expected temperature signature indicative of a fluid leak;

determining, for each of the filtered temperature profiles, an energy profile;

determining, for each of a plurality of the sample distance points, whether the energy profile exceeds an energy threshold; and

generating leak condition signals for sample distance points based on the corresponding energy threshold determination,

wherein the leak condition signals comprise leak condition tracks that are generated by applying a track filter to successive energy threshold determinations for a particular sample distance point.

2. The method as recited in claim 1 , wherein the sensing element is a distributed fiber optic sensor.

3. The method as recited in claim 1 , wherein the sensing element comprises an array of Fiber Bragg Gratings disposed along the length of an optical fiber.

4. The method as recited in claim 1 , wherein determining the energy profile comprises determining, for each of the plurality of the sample distance points, a sum of signal energies within a range on each side of the particular sample distance point.

5. The method as recited in claim 4 , wherein determining whether the energy profile exceeds the threshold energy comprises calculating the threshold energy for corresponding sample distance points, wherein the threshold energy for a sample distance point is a weighted sum of the energy within a range of sample distance points in which that particular sample distance point is centered.

6. The method as recited in claim 1 , wherein the track filter is a M-out-of-N filter, and wherein the track filter initiates a leak condition track if at least M out of N most recent energy threshold determinations is indicative of a fluid leak, wherein M is less than or equal to N.

7. The method as recited in claim 1 , further comprising:

spatially filtering the temperature profiles to generate second filtered temperature profiles that are limited to a second set of spatial frequencies that corresponds to a second expected temperature signature indicative of a fluid leak;

determining, for each of the second filtered temperature profiles, a second energy profile;

determining, for each of a plurality of the sample distance points, whether the second energy profile exceeds an energy threshold; and

generating second leak condition signals for sample distance points based on the corresponding energy threshold determination.

8. The method as recited in claim 7 , further comprising generating an alarm signal if any one of the leak condition signals and second leak condition signals is indicative of a fluid leak.

9. The method as recited in claim 1 , wherein the sensing element extends along the length of a plurality of pipelines and the DTS system is operated to obtain temperature profiles along each of the pipelines.

10. The method as recited in claim 1 , wherein a second sensing element extends along the length of the pipeline, and the method further comprises:

operating the DTS system to obtain second temperature profiles from the second sensing element;

spatially filtering the second temperature profiles to generate second filtered temperature profiles that are limited to a set of spatial frequencies that corresponds to an expected temperature signature indicative of a fluid leak;

determining, for each of the second filtered temperature profiles, a second energy profile;

determining, for each of a plurality of the sample distance points, whether the second energy profile exceeds an energy threshold; and

generating second leak condition signals for sample distance points based on the corresponding energy threshold determination.

11. A method, comprising:

operating a distributed temperature sensing (DTS) system to obtain a time sequence of temperature profiles from a fiber optic sensing element deployed proximate a pipeline that transports a fluid;

spatially filtering the time sequence of temperature profiles to generate filtered temperature profiles that are limited to a set of spatial frequencies that corresponds to expected temperature signatures at distance points along the sensing element that are indicative of one or more leak conditions;

determining, for each of a plurality of the distance points, whether an energy component of the filtered temperature profiles exceeds a threshold energy for that distance point; and

based on the determination, generating an alarm signal identifying a fluid leak at one or more of the distance points,

wherein generating the alarm signal comprises initiating, for each of the plurality of distance points, a leak condition track based on determining that the energy component exceeds the threshold energy for that distance point.

12. The method as recited in claim 11 , further comprising determining the threshold energy for each of the plurality of the distance points based on a weighted sum of the energy within a range of distance points in which that particular distance point is located.

13. The method as recited in claim 11 , wherein the leak condition track is initiated based on determining that the energy component exceeds the threshold energy for that distance point in at least M out of N successive filtered temperature profiles in the time sequence, wherein M is less than or greater than N.

14. A method of detecting leaks from a conduit, comprising:

operating a distributed temperature sensing (DTS) system to obtain temperature profiles from a sensing element deployed along a length of a conduit that is carrying a fluid, wherein the temperature profiles are measures of temperature at sample distance points along the sensing element;

determining, for each of the temperature profiles, whether an energy component of the temperature profile exceeds an energy threshold; and

generating leak condition signals for sample distance points based on the corresponding energy threshold determination,

wherein the leak condition signals comprise leak condition tracks that are generated by applying a track filter to successive energy threshold determinations for a particular sample distance point.

15. The method as recited in claim 14 , wherein the sensing element is a distributed fiber optic sensor.

16. The method as recited in claim 14 , wherein the sensing element comprises an array of Fiber Bragg Gratings disposed along the length of an optical fiber.

17. The method as recited in claim 14 , wherein the track filter is a M-out-of-N filter, and wherein the track filter initiates a leak condition track if at least M out of N most recent energy threshold determinations is indicative of a fluid leak, wherein M is less than or equal to N.

18. The method as recited in claim 14 , further comprising generating an alarm signal if any one of the leak condition signals is indicative of a fluid leak.

19. The method as recited in claim 14 , wherein the conduit is a pipeline, and wherein the fluid is a hydrocarbon fluid.