A method and a system are provided, in which acoustic signals received by distributed acoustic sensors are processed in order to determine the position of a source or sources of the acoustic signals. The method and system are able to determine the position of several acoustic sources simultaneously,
A method and a system are provided, in which acoustic signals received by distributed acoustic sensors are processed in order to determine the position of a source or sources of the acoustic signals. The method and system are able to determine the position of several acoustic sources simultaneously, by measuring the corresponding several acoustic signals. Furthermore, the strength of the acoustic signal or signals can be determined. The location of the acoustic source may be overlaid on a map of an area being monitored, or be used to generate an alarm if perceived to correspond to a threat or an intrusion, for example in a pipeline monitoring application. Alternatively, the method and systems can be used to monitor a hydraulic fracturing process.
대표청구항▼
1. A method of determining a location of an acoustic source, the method comprising: providing a distributed optical fibre sensor in an area to be monitored, the distributed optical fibre sensor being deployed in a known location;receiving an acoustic signal from the acoustic source at a plurality of
1. A method of determining a location of an acoustic source, the method comprising: providing a distributed optical fibre sensor in an area to be monitored, the distributed optical fibre sensor being deployed in a known location;receiving an acoustic signal from the acoustic source at a plurality of sensing regions spatially distributed along a length of the distributed optical fibre sensor such that the acoustic signal is received at the respective sensing regions at different respective times to thereby obtain a first two dimensional spatiotemporal data set; andprocessing the received acoustic signals to determine the location of the acoustic source relative to at least one sensing region along the length of the distributed optical fibre sensor;wherein the processing the received acoustic signals comprises evaluating a plurality of cost functions for one or more of the received acoustic signals, wherein evaluating one of the plurality of cost functions comprises: time shifting the first spatiotemporal data set in dependence on positions of the sensing regions along the length of the distributed optical fibre sensor at which the acoustic signal is received and an estimate value for a shortest distance between the acoustic source and the distributed optical fibre sensor to obtain a time-delayed two dimensional spatiotemporal data set; andcalculating the cost function based on the time-delayed spatiotemporal data set;wherein the processing further comprises selecting a maximum cost function from the plurality of cost functions, the estimate value used to calculate the maximum cost function being an actual shortest distance between the acoustic source and the distributed optical fibre sensor. 2. The method according to claim 1, wherein the distributed optical fibre sensor comprises an interferometer configured to determine optical phase angle data corresponding to the acoustic signal. 3. The method according to claim 1, wherein the distributed optical fibre sensor employs coherent Rayleigh noise methods to measure the acoustic signal. 4. A method of monitoring a hydraulic fracturing process comprising the method of claim 1, and further comprising: i) deploying a distributed optical fibre sensor in the vicinity of oil- or gas-bearing shale to be fractured by the hydraulic fracturing process; andii) injecting water and/or chemicals into the oil- or gas-bearing shale and determining the location of at least one resulting acoustic event. 5. A surveillance method comprising the method of claim 1, comprising deploying a distributed optical fibre sensor in the vicinity of an asset or location to be monitored; wherein the distributed optical fibre sensor is optionally deployed on or along the asset, or around the location. 6. A method of determining a location of an acoustic source, the method comprising: providing a distributed optical fibre sensor in an area to be monitored, the distributed optical fibre sensor being deployed in a known location;receiving an acoustic signal from the acoustic source at a plurality of sensing regions spatially distributed along a length of the distributed optical fibre sensor such that the acoustic signal is received at the respective sensing regions at different respective times to thereby obtain a first two dimensional spatiotemporal data set; andprocessing the received acoustic signals to determine the location of the acoustic source relative to at least one sensing region along the length of the distributed optical fibre sensor,wherein processing the received acoustic signals comprises separating an acoustic signal received at the plurality of sensing regions into its component frequencies and evaluating a plurality of cost functions for one or more of the received acoustic signals, wherein evaluating one of the plurality of cost functions comprises: phase shifting the first spatiotemporal data set in dependence on an estimate value of the shortest distance between the acoustic source and the distributed optical fibre, one or more of the component frequencies and a known speed of sound for the one or more component frequencies through the surrounding medium to obtain one or more phase-shifted two dimensional spatiotemporal data sets; andcalculating the cost function based on the phase shifted spatiotemporal data set,wherein the processing further comprises selecting a maximum cost function from the plurality of cost functions, the estimate value used to calculate the maximum cost function being the actual shortest distance between the acoustic source and the distributed optical fibre sensor. 7. The method according to claim 6, wherein the distributed optical fibre sensor comprises an interferometer configured to determine optical phase angle data corresponding to the acoustic signal. 8. The method according to claim 6, wherein the distributed optical fibre sensor employs coherent Rayleigh noise methods to measure the acoustic signal. 9. A method of monitoring a hydraulic fracturing process comprising the method of claim 6, and further comprising: i) deploying a distributed optical fibre sensor in the vicinity of oil- or gas-bearing shale to be fractured by the hydraulic fracturing process; andii) injecting water and/or chemicals into the oil- or gas-bearing shale and determining the location of at least one resulting acoustic event. 10. A surveillance method comprising the method of claim 6, comprising deploying a distributed optical fibre sensor in the vicinity of an asset or location to be monitored, wherein the distributed optical fibre sensor is optionally deployed on or along the asset, or around the location. 11. The surveillance method of claim 10, wherein the method comprises correlating the determined position of an acoustic source with one or more position related data, wherein the position of the acoustic source is overlaid on a corresponding map of an area being monitored. 12. The surveillance method of claim 10, comprising determining the nature of the acoustic source as a function of the duration of a corresponding acoustic event, the frequency of the acoustic signal, and/or the amplitude of the acoustic event. 13. The surveillance method of claim 10, comprising determining the spatial relationship between the source and an asset to be protected based on the measured position of the acoustic source with respect to the acoustic sensor and producing an alarm or alert responsive to the determined spatial relationship. 14. An apparatus for locating an acoustic source, the apparatus comprising: a distributed optical fibre sensor deployed in an area to be monitored and arranged to receive an acoustic signal from the acoustic source at a plurality of sensing regions spatially distributed along its length such that the acoustic signal is received at the respective sensing regions at different respective times to thereby obtain a first two dimensional spatiotemporal data set; andprocessing means configured to process the received acoustic signals to determine the location of the acoustic source relative to at least one of the sensing regions along the length of the distributed optical fibre sensor;wherein the processing means is further arranged to evaluate a plurality of cost functions for one or more of the received acoustic signals, wherein evaluating one of the plurality of cost functions comprises: time shifting the first spatiotemporal data set in dependence on positions of the sensing regions along the length of the distributed optical fibre sensor at which the acoustic signal is received and an estimate value for a shortest distance between the acoustic source and the distributed optical fibre sensor to obtain a time-delayed two dimensional spatiotemporal data set; andcalculating the cost function based on the time-delayed spatiotemporal data sets;wherein the processing means is further arranged to select a maximum cost function from the plurality, the estimate value used to calculate the maximum cost function being an actual shortest distance between the acoustic source and the distributed optical fibre sensor. 15. A downhole monitoring apparatus comprising the apparatus of claim 14, the distributed optical fibre sensor being deployed in the vicinity of oil- or gas-bearing shale to be fractured by a hydraulic fracturing process. 16. A surveillance apparatus comprising the apparatus of claim 14, the at least one distributed optical fibre sensor being deployed in the vicinity of an asset or location to be monitored. 17. An apparatus for locating an acoustic source, the apparatus comprising: a distributed optical fibre sensor deployed in an area to be monitored and arranged to receive an acoustic signal from the acoustic source at a plurality of sensing regions spatially distributed along its length such that the acoustic signal is received at the respective sensing regions at different respective times to thereby obtain a first two dimensional spatiotemporal data set; andprocessing means configured to process the received acoustic signals to determine the location of the acoustic source relative to at least one of the sensing regions along the length of the distributed optical fibre sensor,wherein the processing means is further arranged to separate an acoustic signal received at the plurality of sensing regions into its component frequencies and evaluate a plurality of cost functions for one or more of the received acoustic signals, wherein evaluating one of the plurality of cost functions comprises: phase shifting the first spatiotemporal data set in dependence on an estimate value of the shortest distance between the acoustic source and the distributed optical fibre, one or more of the component frequencies and a known speed of sound for the one or more component frequencies through the surrounding medium to obtain one or more phase shifted two dimensional spatiotemporal data sets; andcalculating the cost function based on the phase shifted spatiotemporal data set,wherein the processing means is further arranged to select a maximum cost function from the plurality of cost functions, the estimate value used to calculate the maximum cost function being the actual shortest distance between the acoustic source and the distributed optical fibre sensor. 18. A downhole monitoring apparatus comprising the apparatus of claim 17, the distributed optical fibre sensor being deployed in the vicinity of oil- or gas-bearing shale to be fractured by a hydraulic fracturing process. 19. A surveillance apparatus comprising the apparatus of claim 17, the at least one distributed optical fibre sensor being deployed in the vicinity of an asset or location to be monitored.
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Showen Robert L. ; Dunham Jason W., Automatic real-time gunshot locator and display system.
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