Flow monitoring using fibre optic distributed acoustic sensors
First Claim
1. A method of monitoring fluid flow along a conduit comprising:
- introducing an acoustic stimulus into the fluid within the conduit wherein the acoustic stimulus comprises at least one acoustic pulse having a time varying frequency and/or at least one pulse having a broadband frequency spectrum;
interrogating an optical fibre deployed along the path of the conduit to provide a distributed acoustic sensor having a plurality of sensing portions of fibre; and
analysing acoustic signals detected by said plurality of sensing portions of fibre in response to said acoustic stimulus to determine at least one flow characteristic,wherein analysing the acoustic signals comprises identifying reflections of said acoustic stimulus caused by the fluid within the conduit and analysing said reflections to determine any Doppler shift in frequency of said reflections of said acoustic stimulus compared to the acoustic stimulus.
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Accused Products
Abstract
This application describes methods and apparatus for monitoring flow of fluids within conduits using fiber optic Distributed Acoustic Sensing (DAS). The method can determine flow rate and/or flow regime within a conduit such as within a production well or a pipeline. Embodiments involve introducing an acoustic stimulus (802) into the fluid within the conduit (801); interrogating an optical fiber (104) deployed along the path of the conduit to provide a DAS sensor; and analyzing the acoustic signals detected by a plurality of channels of the DAS sensor to determine at least one flow characteristic. Analyzing the acoustic signal comprises identifying reflections (804) of said acoustic stimulus caused by the fluid within the conduit and analyzing said reflections to determine any Doppler shift (Δf).
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Citations
23 Claims
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1. A method of monitoring fluid flow along a conduit comprising:
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introducing an acoustic stimulus into the fluid within the conduit wherein the acoustic stimulus comprises at least one acoustic pulse having a time varying frequency and/or at least one pulse having a broadband frequency spectrum; interrogating an optical fibre deployed along the path of the conduit to provide a distributed acoustic sensor having a plurality of sensing portions of fibre; and analysing acoustic signals detected by said plurality of sensing portions of fibre in response to said acoustic stimulus to determine at least one flow characteristic, wherein analysing the acoustic signals comprises identifying reflections of said acoustic stimulus caused by the fluid within the conduit and analysing said reflections to determine any Doppler shift in frequency of said reflections of said acoustic stimulus compared to the acoustic stimulus. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of monitoring fluid flow along a conduit comprising:
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introducing an acoustic stimulus into the fluid within the conduit; interrogating an optical fibre deployed along the path of the conduit to provide a distributed acoustic sensor having a plurality of sensing portions of fibre; and analysing acoustic signals detected by said plurality of sensing portions of fibre in response to said acoustic stimulus to determine at least one flow characteristic, wherein analysing the acoustic signals comprises identifying reflections of said acoustic stimulus caused by the fluid within the conduit and analysing said reflections to determine any Doppler shift in frequency of said reflections of said acoustic stimulus compared to the acoustic stimulus; the method further comprising transmitting at least one additional acoustic stimulus into the fluid in the conduit to mix with the reflected signal to improve signal to noise ratio.
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19. An apparatus for monitoring fluid flow along a conduit comprising:
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an interrogator unit for interrogating an optical fibre deployed along the path of the conduit to provide a distributed acoustic sensor having a plurality of sensing portions of fibre; and a processor configured to analyse acoustic signals detected by said plurality of sensing portions of fibre with an introduced acoustic stimulus propagating in the fluid within the conduit to determine at least one flow characteristic, wherein said processor is configured to analyse the acoustic signals to identify reflections of said acoustic stimulus caused by the fluid within the conduit and analyse said reflections to determine any Doppler shift in frequency of said reflections of said acoustic stimulus compared to the acoustic stimulus; and wherein said processor is also configured to analyse the detected acoustic signals to determine the rate of propagation of the acoustic stimulus along the conduit and to detect any change in propagation speed along the conduit. - View Dependent Claims (20, 21, 22, 23)
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Specification