Optasense Holdings Limited

Qinetiq Limited

Optosense Holdings Limited

David John Hill

Andrew Biggerstaff Lewis

Magnus McEwen-King

Magnus Mcewen-King

Roger Ian Crickmore

Philip John Nash

Patrick Tindell

Sean Dormer Thomas

Patrick Phillip Tindell

Alastair Godfrey

Menno Mathieu Molenaar

Richard Martin

Jonathan James Westhall

Mark Allen Lee

Richard John Davis

Jonathan Westhall

Jon Richards

William Malcolm Babb

Steven Robert Thomson

Benjamin Hodder

Simon Tanner

Phillip John Nash

Fiber optic cables with improved performance for use in distributed sensing, for instance in distributed acoustic sensors, are disclosed. In one embodiment a fiber optic cable () comprises a core () and cladding () disposed within a buffer material () surrounded by a jacket () and arranged so that the core is offset from the center of the cable. By offsetting the core from the center of the jacket any bending effects on the core can be maximized compared to the core being located at the center of the cable.

Optic fibres and fibre optic sensing

A method for monitoring a fluid carrying conduit by introducing an acoustic pulse into the conduit, and interrogating an optic fibre positioned along the path of said conduit to provide distributed acoustic sensing. By measuring the response at each of a plurality of locations, a conduit condition profile can be derived. A condition profile can be obtained quickly and easily with minimum disruption to the pipeline infrastructure and contained flow. Existing optic fibres running along the path of a pipe can be employed for sensing purposes, allowing relatively long spans of pipeline to be monitored with only limited access to the pipe.

Conduit monitoring

This application relates to methods and apparatus for monitoring hydraulic fracturing in well formation and fracture characterization using distributed acoustic sensing (DAS). The method involves interrogating an optic fiber arranged down the path of a borehole to provide a distributed acoustic sensor and also monitoring flow properties of fracturing liquid pumped into the well where the acoustic data from the distributed acoustic sensor is processed together with the flow properties data to provide an indication of at least one fracture characteristic.

Fracture characterisation

A system for moving object () detection is provided, the system comprising a fiber optic interrogator () adapted to provide distributed acoustic sensing on a optic fiber (), for example arranged along a border. The measurement signals from each of a plurality of sensing portions () of said fiber are analyzed to determined a characteristic of a Doppler shift. The characteristic of a Doppler shift may be a generally continuous decrease in detected frequency. By detecting the time at which the rate of change of frequency is at a maximum for each of the sensing portions the time of closest approach (ti, t, tt, t) of the object to those sensing portions can be determined with the sensing portion the object approaches closest to showing the greatest value of maximum rate of change of frequency. The distance of closest approach and velocity can be determined.

Detection of moving objects

Methods and apparatus for monitoring steam injection in a steam assisted well are disclosed. The method involves obtaining a first temperature profile of a well by performing distributed temperature sensing on a first fiber optic. The method also obtains a second temperature profile of the well by interrogating a second fiber optic to provide distributed sensing of temperature variations. Interrogating the second fiber optic comprises repeatedly launching interrogations of one or more pulses of coherent radiation into said second fiber optic, detecting any radiation which is Rayleigh backscattered from each interrogation and analyzing the detected backscattered radiation to detect any variation between interrogations due to temperature variation. The method combines said first and second temperature profiles to provide a steam injection profile. The method may also involve determining an acoustic profile of the well through distributed acoustic sensing. Measurements from a small number of downwell point temperature and pressure sensors may also be used to determine the steam injection profile.

Monitoring of steam injection

The present application relates to road traffic monitoring to detect the number, speed and/or type of vehicles travelling on a road. Noise features () are deployed on, or formed in, the surface of a road (). The noise feature () is arranged to generate a characteristic acoustic signature when traversed by the wheels of a vehicle () travelling within a lane of the road. A distributed acoustic sensor () is deployed to detect occurrences of the characteristic acoustic signature. In some embodiments the noise element may comprise at least two distinct elements (), for instance rumble strips arranged transversely to the road, which are a known distance apart along the road. The acoustic signals from a wheel crossing both elements can be detected and used to determine the vehicle speed. The number of vehicle axles and axle separation can also be determined to categorize the type of vehicle. A plurality of noise features may be located in different lanes of a multi-lane road with noise features in different lanes arranged to generate different characteristic acoustic signatures.

Traffic monitoring

Fiber optic cable structures suitable for distributed acoustic sensing that are capable of discriminating between stimuli acting on the cable in different directions, the cable structure including a core structure () with an optical fiber wound around the periphery of the core structure, the core further including a mass () which is movable in a preferred direction within the cable such that movement of said mass in said preferred direction causes a change in length of the fiber wound around the periphery of the core.

Fibre optic cable for acoustic/seismic sensing

A method of distributed fiber optic sensing is described in which an optical fiber () is interrogated with electromagnetic radiation; back-scattered radiation is detected; and the returns are processed to provide a measurement signal () for each of a plurality of longitudinal sensing portions of the optical fiber. The method comprises analyzing the measurement signals of a first subset of longitudinal sensing portions to provide a first zone () having a first sensing function and analyzing the measurement signals of at least a second subset of longitudinal sensing portions to provide at least a second zone () having a second, different, sensing function. The different sensing functions may include detecting different events of interest. In some embodiments the geometry of the fiber may provide different sensing zones ().

Fibre optic distributed sensing

Methods and apparatus for downhole monitoring are provided by interrogating an unmodified optic fiber () arranged along the path of a well bore () to provide a distributed acoustic sensor and sampling data gathered from a plurality of contiguous sensing portions of the fiber. The sampled data is processed to determine one or more well bore parameters. The well bore parameters may comprise a well condition profile, and may be obtained in response to an acoustic stimulus.

Well monitoring by means of distributed sensing means

Fiber optic cables with improved performance for use in distributed sensing, for instance in distributed acoustic sensors, are disclosed. In one embodiment a fiber optic cable () comprises a core () and cladding () disposed within a buffer material () and surrounded by a jacket () and arranged so that the core is offset from the center of the cable. By offsetting the core from the center of the jacket any bending effects on the core can be maximised compared with the core being located at the center of the cable.

Techniques for determining lateral offset of the source of an acoustic disturbance in a distributed acoustic fiber optic sensor are described. The sensor comprises an optical source () for interrogating an optical fiber () and a detector () and processor () arranged to detect any backscattered radiation and determine a measurement signal for a plurality of discrete longitudinal sensing portions of the optical fiber. The processor is also arranged to analyse the measurement signals to identify signals corresponding to the same acoustic wave arriving at different parts of the fiber and determine from the time of arrival of said acoustic wave the direction and/or distance of the origin of said acoustic wave from the optical fiber. The geometry of the fiber may be arranged to ensure that any positional ambiguity can be resolved and the use of multiple fibers () is disclosed.

Distributed fibre optic sensing

This invention relates to the fiber optic distributed acoustic sensing to detect P and S waves in a solid medium. Distributed acoustic sensing can be achieved using an unmodified fiber optic by launching optical pulses into the fiber and detecting radiation which is Rayleigh backscattered there from. By analyzing the returns in analysis bins, acoustic disturbances can be detected in a plurality of discrete longitudinal sections of the fiber. The present invention extends such fiber distributed acoustic sensing to detection of S and P waves.

Fibre optic acoustic sensing

This application describes methods and apparatus for downhole monitoring in real-time. The method involves interrogating an unmodified optic fiber () arranged along the path of a well bore () to provide a distributed acoustic sensor and sampling data gathered from a plurality of sensing portions of the fiber. The sampled data is then processed to provide a real-time indication of the acoustic signals detected by the sensing portions of the fiber. The real-time indication provides information to an operator or controller of the downwell process with real-time feedback data regarding what is happening during the downwell process which allows the identification of any problems and adjustment of the process parameters.

A fiber-optic sensor array () comprises a line array of fiber-optic sensor packages (AX, BX, CX, DX, AY, BY, CY, DY, AZ, BZ, CZ, DZ) each having a package input/output (i/o) fiber and each being arranged to output a finite output pulse series of optical output pulses via the package i/o fiber in response to input thereto of one or more interrogating optical pulses. The array further comprises a fiber-optic bus () extending along the length of the line array, each package i/o fiber being optically coupled to the fiber-optic bus at a respective positions along the line array. The array allows interrogation at a higher frequency than is the case for a serial array of the same number of fiber-optic sensing packages.

Fibre optic sensor array

There is provided a system () for magnetic field detection, comprising a fiber optic interrogator () adapted to interrogate a first length of optical fiber () with interrogating radiation, detect radiation backscattered from said optical fiber and analyze said detected radiation to provide distributed sensing indicative of mechanical disturbances of said optical, wherein the optic fiber is mechanically coupled to a material whose dimensions vary dependent on applied magnetic field. Changes in dimensions of the optic fiber as can be detected by virtue of changes in back-scattering of light from said fiber using the principles of fiber optic distributed acoustic sensing.

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Dorchester, United Kingdom

David John Hill