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1. (WO2019000107) METHOD AND SYSTEM FOR DETECTING WHETHER AN ACOUSTIC EVENT HAS OCCURRED ALONG A FLUID CONDUIT
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CLAIMS

A method for determining whether an acoustic event has occurred along a fluid conduit having acoustic sensors positioned therealong, the method comprising:

(a) determining, using a processor and for each of the sensors:

(i) a linear relationship between a measured acoustic signal measured using the sensor and a white noise acoustic source located along a longitudinal segment of the fluid conduit overlapping the sensor; and

(ii) from the linear relationship, an acoustic path response and an acoustic source transfer function that transforms the white noise acoustic source;

(b) monitoring over time variations in one or both of the acoustic path responses and acoustic source transfer functions;

(c) determining whether at least one of the variations exceeds an event threshold; and

(d) when at least one of the variations exceeds the event threshold, attributing the acoustic event to one of the sensors corresponding to the acoustic path response or acoustic source transfer function that varied in excess of the event threshold.

The method of claim 1 wherein the processor attributes the acoustic event to the one of the sensors for which the variation most exceeds the event threshold.

The method of claim 1 wherein the acoustic event comprises one of multiple acoustic events, and wherein the processor attributes one of the acoustic events to each of the sensors for which the variation exceeds the event threshold.

The method of any one of claims 1 to 3 wherein the acoustic path response comprises an acoustic response of the longitudinal segment and the acoustic event is identified as having occurred along the longitudinal segment corresponding to the sensor to which the acoustic event is attributed.

The method of claim 4 wherein, for each of the channels, the processor determines the linear relationship between the measured acoustic signal, the white noise acoustic source located along the longitudinal segment, and white noise acoustic sources located along any immediately adjacent longitudinal segments.

The method of claim 4 or 5 wherein each element of the linear relationship is a parameterized transfer function that is parameterized using a finite impulse response structure.

The method of any one of claims 4 to 6 wherein the processor determines the acoustic path responses and acoustic source transfer functions by factoring the linear relationship using a linear regression, wherein the linear regression is factored into a first array of parameterized transfer functions for determining the acoustic path responses and a second array of parameterized transfer functions for determining the acoustic source transfer functions.

The method of claim 7 wherein each of the first and second arrays is parameterized using a finite impulse response structure.

The method of any one of claims 4 to 8 further comprising, prior to monitoring variations in one or both of the acoustic path responses and acoustic source transfer functions, refining the one or both of the acoustic path responses and acoustic source transfer functions using weighted nullspace least squares.

The method of any one of claims 4 to 9 wherein (b)-(d) comprise:

(a) determining a confidence bound for each of:

(i) two of the acoustic path responses; or

(ii) two of the acoustic source transfer functions;

(b) from the confidence bounds, determining a statistical distance between the two of the acoustic source responses or the two of the acoustic source transfer functions;

(c) comparing the statistical distance to the event threshold; and

(d) identifying the acoustic event as having occurred when the statistical distance exceeds the event threshold.

The method of any one of claims 4 to 10 further comprising dividing the measured acoustic signal into blocks of a certain duration prior to determining the linear relationship.

The method of any one of claims 4 to 11 wherein each of the longitudinal segments is delineated by a pair of fiber Bragg gratings located along an optical fiber and tuned to substantially identical center wavelengths, and further comprising optically interrogating the optical fiber in order to obtain the measured acoustic signal.

The method of claim 12 wherein the optical fiber extends parallel to the fluid conduit.

The method of claim 12 wherein the optical fiber is wrapped around the fluid conduit.

The method of claim 13 or 14 wherein the optical fiber is within a fiber conduit laid adjacent the fluid conduit.

The method of any one of claims 4 to 15 wherein the fluid conduit comprises a pipeline.

A system for detecting whether an acoustic event has occurred along a fluid conduit longitudinally divided into measurements channels, the system comprising:

(a) an optical fiber extending along the conduit and comprising fiber Bragg gratings (FBGs), wherein each of the measurement channels is delineated by a pair of the FBGs tuned to substantially identical center wavelengths;

(b) an optical interrogator optically coupled to the optical fiber and configured to optically interrogate the FBGs and to output an electrical measured acoustic signal; and

(c) a signal processing unit comprising:

(i) a processor communicatively coupled to the optical interrogator; and

(ii) a non-transitory computer readable medium communicatively coupled to the processor, wherein the medium has computer program code stored thereon that is executable by the processor and that, when executed by the processor, causes the processor to perform the method of any one of claims 1 to 12.

The system of claim 17 wherein the optical fiber extends parallel to the fluid conduit.

The system of claim 17 wherein the optical fiber is wrapped around the fluid conduit.

The system of claim 17 further comprising a fiber conduit adjacent the fluid conduit, wherein the optical fiber extends within the fiber conduit.

The system of any one of claims 17 to 20 wherein the fluid conduit comprises a pipeline.

A non-transitory computer readable medium having stored thereon computer program code that is executable by a processor and that, when executed by the processor, causes the processor to perform the method of any one of claims 1 to 16.