Fluid flow measurement using optical fibres
First Claim
1. A method of monitoring fluid flow comprising:
- providing an optical fibre having a heatable coating comprising optically absorbing material, the heatable coating provided as a layer around the outer surface of the optical fibre extending axially along the optical fibre;
disposing the optical fibre so that the heatable coating is in thermal contact with flowing fluid;
heating the heatable coating, by exposing the heatable coating to light at a wavelength that is absorbed by the optically absorbing material, so that heat is transferred from the coating to the fluid;
launching light into the optical fibre;
detecting light from the optical fibre;
processing the detected light to obtain information indicative of the temperature of the heatable coating, where the temperature of the heatable coating depends on the flow; and
using the information indicative of the temperature of the heatable coating to derive information about the flow.
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Accused Products
Abstract
A method of monitoring fluid flow uses an optical fiber having a heatable coating. The fiber is disposed within flowing fluid, and the heatable coating heated so that heat is transferred from the coating to the fluid. Optical measurements of the temperature of the heatable coating are made, where the temperature of the heatable coating depends on the flow velocity of the flowing fluid, and the temperature measurement is used to derive information about the flow. The coating may be an electrically resistive layer on the outer surface of the fiber, that is heated by passing electric current through it. This allows distributed flow measurements to be made. Alternatively, discrete measurements can be made if the coating is provided as a thin film layer on an end facet of the fiber. The coating is heated by directing light at a wavelength absorbed by the thin film material along the fiber.
34 Citations
54 Claims
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1. A method of monitoring fluid flow comprising:
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providing an optical fibre having a heatable coating comprising optically absorbing material, the heatable coating provided as a layer around the outer surface of the optical fibre extending axially along the optical fibre; disposing the optical fibre so that the heatable coating is in thermal contact with flowing fluid; heating the heatable coating, by exposing the heatable coating to light at a wavelength that is absorbed by the optically absorbing material, so that heat is transferred from the coating to the fluid; launching light into the optical fibre; detecting light from the optical fibre; processing the detected light to obtain information indicative of the temperature of the heatable coating, where the temperature of the heatable coating depends on the flow; and using the information indicative of the temperature of the heatable coating to derive information about the flow. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of monitoring fluid flow comprising:
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providing an optical fibre having a heatable coating; disposing the optical fibre so that the heatable coating is in thermal contact with flowing fluid; heating the heatable coating so that heat is transferred from the coating to the fluid; launching light into the optical fibre; detecting light from the optical fibre; processing the detected light to obtain information indicative of the temperature of the heatable coating, where the temperature of the heatable coating depends on the flow; using the information indicative of the temperature of the heatable coating to derive information about the flow, wherein the launching light, detecting light and processing light comprises operating the optical fibre as a distributed temperature sensor, and the using the information indicative of the temperature of the heatable coating to derive information about the flow comprises identifying changes in temperature along the length of the fibre, such a change indicating the location of a change in the flow of the fluid. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. Apparatus for monitoring fluid flow, comprising:
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an optical fibre having a heatable coating for disposing in thermal contact with flowing fluid, the heatable coating comprising optically absorbing material and provided as a layer around the outer surface of the optical fibre extending axially along the optical fibre; an optical power source operable to heat the heatable coating, by exposing the heatable coating to light at a wavelength that is absorbed by the optically absorbing material, so that heat is transferred from the coating to the fluid; an optical source operable to generate light and launch the light into the optical fibre; a photodetector operable to detect light from the optical fibre; and a processor operable to process the detected light to obtain information indicative of the temperature of the heatable coating, where the temperature of the heatable coating depends on the flow. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 47)
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35. Apparatus for monitoring fluid flow, comprising:
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an optical fibre having a heatable coating for disposing in thermal contact with flowing fluid; a power source operable to heat the heatable coating so that heat is transferred from the coating to the fluid; an optical source operable to generate light and launch the light into the optical fibre; a photodetector operable to detect light from the optical fibre; and a processor operable to process the detected light to obtain information indicative of the temperature of the heatable coating, where the temperature of the heatable coating depends on the flow, wherein the optical source, the photodetector and the processor are operable to enable operation of the optical fibre as a distributed temperature sensor, and the processor is further operable to use the information indicative of the temperature of the heatable coating to derive information about the flow by identifying changes in temperature along the length of the fibre, such a change indicating the location of a change in the flow of the fluid. - View Dependent Claims (36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46)
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48. A method of monitoring fluid flow in an oil well, comprising:
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providing an optical fibre having a heatable coating provided as a layer around the outer surface of the optical fibre extending axially along the optical fibre; deploying the optical fibre downhole in an oil well such that the heatable coating is in thermal contact with flowing fluid; heating the heatable coating so that heat is transferred from the coating to the fluid; launching light into the optical fibre; detecting light from the optical fibre; processing the detected light to obtain information indicative of the temperature of the heatable coating, where the temperature of the heatable coating depends on the flow; and using the information indicative of the temperature of the heatable coating to derive information about the flow, wherein the launching light, detecting light and processing the detected light are performed so as to obtain the information indicative of the temperature of the heatable coating in the form of a distributed temperature profile over the length of the optical fibre. - View Dependent Claims (49, 50, 51, 52, 53)
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54. A method of detecting scale within a well bore, comprising:
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providing an optical fibre having a heatable coating; deploying the optical fibre downhole within a well bore so that the heatable coating is in thermal contact with fluid flowing within the well bore; heating the heatable coating so that heat is transferred from the coating to the fluid; launching light into the optical fibre; detecting light from the optical fibre; processing the detected light to obtain information indicative of any variation in temperature of the heatable coating with depth within the well bore, where the temperature of the heatable coating depends on the flow of the fluid; monitoring the temperature information for any changes in temperature of the heatable coating with depth within the well bore; and identifying any change in temperature with a change in fluid flow within the well bore caused by scale deposition at that depth.
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Specification