Structure monitoring
First Claim
1. A method of monitoring a shape of a subsea riser, comprising:
- deploying a plurality of acoustic sources at known positions in an area in which the subsea riser to be monitored is located;
deploying an optical fiber distributed acoustic sensor on the subsea riser, the subsea riser being tethered between two points and free to change shape between the two points, and the optical fiber distributed acoustic sensor comprising a sensing optical fiber that extends along the subsea riser and is affixed to the subsea riser in a known relationship with respect to the subsea riser such that it is known which part of the optical fiber is adjacent and connected to which part of the subsea riser;
emitting positioning acoustic signals from the plurality of acoustic sources;
using the optical fiber distributed acoustic sensor to detect, at a plurality of acoustic sensor positions along the sensing optical fiber, the positioning acoustic signals emitted by the plurality of acoustic sources;
calculating relative positions of a plurality of the acoustic sensors in dependence on the detected acoustic signals from the acoustic sources; and
from the calculated positions of the sensors along the fiber, determining a shape of the subsea riser in dependence on the known relationship between the fiber and the subsea riser.
2 Assignments
0 Petitions
Accused Products
Abstract
A method and apparatus for monitoring a structure using an optical fiber based distributed acoustic sensor (DAS) extending along the length of the structure. The DAS is able to resolve a separate acoustic signal with a spatial resolution of 1 m along the length of the fibre, and hence is able to operate with an acoustic positioning system to determine the position of the riser with the same spatial resolution. In addition, the fiber can at the same time also detect much lower frequency mechanical vibrations in the riser, for example such as resonant mode vibrations induced by movement in the surrounding medium. By using vibration detection in combination with acoustic positioning then overall structure shape monitoring can be undertaken, which is useful for vortex induced vibration (VIV) visualisation, fatigue analysis, and a variety of other advanced purposes. The structure may be a sub-sea riser.
48 Citations
22 Claims
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1. A method of monitoring a shape of a subsea riser, comprising:
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deploying a plurality of acoustic sources at known positions in an area in which the subsea riser to be monitored is located; deploying an optical fiber distributed acoustic sensor on the subsea riser, the subsea riser being tethered between two points and free to change shape between the two points, and the optical fiber distributed acoustic sensor comprising a sensing optical fiber that extends along the subsea riser and is affixed to the subsea riser in a known relationship with respect to the subsea riser such that it is known which part of the optical fiber is adjacent and connected to which part of the subsea riser; emitting positioning acoustic signals from the plurality of acoustic sources; using the optical fiber distributed acoustic sensor to detect, at a plurality of acoustic sensor positions along the sensing optical fiber, the positioning acoustic signals emitted by the plurality of acoustic sources; calculating relative positions of a plurality of the acoustic sensors in dependence on the detected acoustic signals from the acoustic sources; and from the calculated positions of the sensors along the fiber, determining a shape of the subsea riser in dependence on the known relationship between the fiber and the subsea riser. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A system for monitoring a shape of a subsea riser, comprising:
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a plurality of acoustic sources at known positions in an area in which the subsea riser to be monitored is located; an optical fiber distributed acoustic sensor deployed on the subsea riser, the subsea riser being tethered between two points and free to change shape between the two points, and the optical fiber distributed acoustic sensor comprising a sensing optical fiber that extends along the subsea riser and is affixed to the subsea riser in a known relationship with respect to the subsea riser such that it is known which part of the optical fiber is adjacent and connected to which part of the subsea riser; and a processor arranged to receive acoustic data from the optical fiber distributed acoustic sensor representative of detected acoustic signals detected by the optical fiber distributed acoustic sensor, wherein in use; a) the optical fiber distributed acoustic sensor detects, at a plurality of acoustic sensor positions along the fiber, acoustic signals emitted by the plurality of acoustic sources; and b) the processor; i. calculates relative positions of a plurality of the acoustic sensors in dependence on the acoustic data representative of the detected acoustic signals from the acoustic sources; and ii. from the calculated positions of the sensors along the fiber, determines a shape of the subsea riser in dependence on the known relationship between the fiber and the subsea riser. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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Specification