A fibre optic sensing apparatus (400) is described which has an optical output path (403, 405, 404) configured to repeatedly interrogate a sensing optical fibre (402) by launching coherent optical radiation into the sensing optical fibre. A detector (407) is configured to receive optical radiation that is Rayleigh backscattered from the sensing optical fibre and output a detected backscatter signal in response to each interrogation and a processor (408) processes the detected backscatter signal. The apparatus is operable in a frequency swept mode, in which the sensing optical fibre is interrogated with a first set of interrogations of coherent optical radiation having different optical frequencies from one another to acquire, for at least one sensing portion of the sensing optical fibre, a backscatter spectral profile (201) of a measurement value of the detected backscatter signal with frequency across a first frequency range. The processor is configured to combine a plurality of said backscatter spectral profiles (201, 202) to form a reference profile (203) with an effective frequency range greater than the first frequency range.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
This application relates to fibre optic cables structures which are particularly suited for use for distributed fibre optic sensing. A fibre optic cable structure (300, 500) is described which includes a cable core (301, 501) and a longitudinal strength member (302, 502). The cable core has at least one optical fibre (301a, 501a) and, optionally, one or more surrounding layers (505) and/or a strain transformer. (504) The cable core and is fixedly coupled to the longitudinal strength member at periodic fixed coupling points (303, 503). At the fixed coupling points the cable core has a substantially fixed position with respect to the longitudinal strength member and between the fixed coupling points the cable core is free to move with respect to the strength member. For an operating range of tensile load and pressure, the length (Lcoup) of the cable core between any two adjacent fixed coupling points is greater than the axial distance (Dcoup) along the fibre optic cable structure between the fixed anchoring points.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
This application describes methods and apparatus for fibre optic sensing. A receive unit (102) includes an optical arrangement configured to receive coherent optical radiation that has propagated through a sensing optical fibre (102) and to form first and second optical signals, wherein the second optical signal comprises optical radiation received from the sensing optical fibre later than the optical radiation of the first optical signal by a defined time period (∆t). A photodetector (15) detects the first optical signal mixed with the second optical signal and a processor (106) demodulates a derivative signal formed by interference of the first and second optical signals. First and second receive units (103a, 103b) may be located at opposite ends of a cable structure to provide respective measurement signals and a signal processor (302) can process the two measurement signals to locate a disturbance.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
This application relates to methods and apparatus for distributed fibre optic sensing. A sensing apparatus (200) includes an optical arrangement (103, 201, 104) which repeatedly interrogates a sensing optical fibre (102) by launching coherent interrogating optical radiation into the sensing optical fibre. A detector (105) detects Rayleigh backscatter from within the sensing fibre and a processor (204) processes the detected backscatter to determine a measurement signal for each of a plurality of channels of the sensing optical fibre. The wavelength of the coherent interrogating optical radiation is modulated (201) so as to vary between successive interrogations according to a modulation characteristic. The processor (204) is operable to identify, for a given channel, an induced signal component corresponding to the modulation characteristic and determine an amplitude of the induced signal component so as to determine a compensation to be applied to the measurement signal for that channel to compensate for any variation in effective gauge length.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
G01K 11/32 - Mesure de la température basée sur les variations physiques ou chimiques, n'entrant pas dans les groupes , , ou utilisant des changements dans la transmittance, la diffusion ou la luminescence dans les fibres optiques
This application relates to methods and apparatus for distributed fibre optic sensing. The apparatus includes an optical arrangement (103, 104, 105) configured to generate a local oscillator signal (LO) and also to repeatedly interrogate a sensing optical fibre (102). Each interrogation comprises at least one pulse of coherent optical radiation at a launch frequency which differs from that of the local oscillator signal by a carrier frequency. A mixer 9107) mixes backscatter signal from the sensing fibre with the local oscillator signal; and a detector arrangement (108X, 108Y) provides at least one corresponding digital detector output signal (DX, DY) A processor (110) processes each digital detector output signal to down-convert (202) the digital detector output signal to a respective baseband signal based for each carrier frequency and convert (206) each baseband signal to a phase signal. The processor is operable to apply time-domain low pass filtering (301) to each baseband signal with a cut-off frequency which is less than half the interrogation rate.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
This application relates to distributed fibre optic sensing. A sensor apparatus (200) includes an interrogator (201) for repeatedly interrogating a sensing optical fibre (102) with interrogating optical radiation and detecting radiation which is Rayleigh backscattered from within the sensing fibre. In a first, polarisation sensing mode of operation, the interrogator (201) is optically coupled to the sensing fibre (102) via an optical system (202) that includes a length (203) of optical fibre upstream of a polariser (204) and the interrogator is configured to output coherent optical radiation with an optical power such that the interrogating radiation experiences non-linear effects when propagating in the length (203) of optical fibre, so as to reduce coherence of the interrogating radiation. In the first mode, the interrogator determines the extent of any variation in polarisation of the backscatter radiation. The apparatus may also be operable in a second, coherent sensing mode in which the interrogator outputs optical radiation below a non-linear threshold.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
This application describes a distributed fibre optic sensing apparatus (100), for instance a DAS sensor. The sensing apparatus includes an optical source (105, 106) for repeatedly interrogating an optical fibre (101) with interrogating optical radiation having an optical power such that the interrogating optical radiation experiences spectral spreading when propagating in the optical fibre. A detector (107) is configured receive Rayleigh backscatter from within the sensing fibre and a narrowband filter (109), with a passband at the launch frequency of the interrogating radiation, filters the backscatter. The optical source is operable such that an interval between repeated interrogations is less than a round trip travel time for the interrogating optical radiation to a distal end of the optical fibre, which thus can allow for an improved ping rate for a region of interest.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
This application describes a fibre optic cable structure which is advantageous for distributed fibre optic sensing, for example distributed acoustic sensing (DAS). The fibre optic cable structure (200, 500, 600) includes an optical fibre (101) for distributed fibre optic sensing and is configured to comprise at least one longitudinal section of a first type (201), which exhibits a change in effective optical path length of the optical fibre of one polarity in response to a given applied force, and which is adjacent to at least one longitudinal section of a second type (202), which exhibits a change in effective optical path length of the optical fibre of the opposite polarity in response to an equivalent applied force. When used for DAS, the response of a sensing portion that includes sections of both the first and second types, will include or exclude certain wavenumber by summation, which provides a directional sensitivity to incident waves.
G01L 1/24 - Mesure des forces ou des contraintes, en général en mesurant les variations des propriétés optiques du matériau quand il est soumis à une contrainte, p.ex. par l'analyse des contraintes par photo-élasticité
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
G01L 5/105 - Appareils ou procédés pour la mesure des forces, du travail, de la puissance mécanique ou du couple, spécialement adaptés à des fins spécifiques pour la mesure de la tension dans les éléments flexibles, p.ex. dans les cordages, les câbles, les fils métalliques, les filaments, les courroies ou les bandes en utilisant des moyens électriques en utilisant des moyens électro-optiques
G01L 5/166 - Appareils ou procédés pour la mesure des forces, du travail, de la puissance mécanique ou du couple, spécialement adaptés à des fins spécifiques pour la mesure de plusieurs composantes de la force en utilisant des moyens photoélectriques
G01M 5/00 - Examen de l'élasticité des structures ou ouvrages, p.ex. fléchissement de ponts ou d'ailes d'avions
G02B 6/44 - Structures mécaniques pour assurer la résistance à la traction et la protection externe des fibres, p.ex. câbles de transmission optique
A fibre optic cable structure (300) suitable for fibre optic sensing with an improved sensitivity to an environmental parameter is described. The structure (300) includes an optical fibre (301) and a bend inducer (304) responsive to the environmental parameter to control bending of the optical fibre. The bend inducer (304) is configured to adopt a first configuration, that induces a first curvature of the optical fibre, at a first value of the environmental parameter and to adopt a second configuration at a second, different, value of the environmental parameter that induces a second, different, curvature of the optical fibre. By action of the bend inducer (304) a change in value of the environmental parameter imparts a bending force on the optical fibre.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
This application relates to methods and apparatus for communication using fibre optic sensing techniques. A communication apparatus (210) has a first optical fibre (101) coupled to a first material (212) configured to vary in dimension in response to a variation in applied magnetic field (221), such that, a strain is induced in the first optical fibre (101) due to the variation in applied magnetic field. A fibre optic interrogator (102) is configured to interrogate the first optical fibre (101) with optical radiation to provide sensing and provide at least one first measurement signal indicative of variations in applied magnetic field. A processor (103) is configured to analyse said at least one first measurement signal to detect a characteristic signature indicative of a data transmission. In use a transmitter (220) can transmit data by deliberately modulating a generated magnetic field (221) in the vicinity of the optical fibre (101).
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
H04B 10/00 - Systèmes de transmission utilisant des ondes électromagnétiques autres que les ondes hertziennes, p.ex. les infrarouges, la lumière visible ou ultraviolette, ou utilisant des radiations corpusculaires, p.ex. les communications quantiques
H04B 10/25 - Dispositions spécifiques à la transmission par fibres
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
This application described methods and apparatus for distributed fibre optic sensing. A sensing apparatus (100) has a modulator (105) which modulates radiation from an optical source (103) to interrogate a sensing optical fibre (102) with a first interrogation pulse at a first frequency (F1) and a second interrogation pulse at a second, different, frequency (F2), both different in frequency from a local oscillator (LO). A mixer (107) mixes backscatter from the sensing optical fibre with the local oscillator and supplies the mixed signal to a detector (108) that provides a corresponding digital signal. A processor (110) processes the digital signal (DX, DY) in a first and second processing channels to demodulate respective first and second phase signals based on the respective frequency difference between the first and second frequency and the local oscillator and determines a temporal difference between the first and second phase signals.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
This application relates to methods and apparatus for distributed fibre optic sensing that can provide an indication of the absolute value of pressure acting on a sensing portion of a fibre optic cable. A sensor apparatus (600) has a first fibre optic cable structure (102) comprising a first optical fibre (101) and an interrogator (103) configured to perform distributed acoustic sensing on the first optical fibre (101) to provide a measurement signal from at least one sensing portion of the first optical fibre. The first fibre optic cable structure (102) is configured such that a sensitivity of a sensing portion (603, 604) to an incident pressure stimulus (ΔP1, ΔP2) depends on the ambient pressure (AP1, AP2) at the location of the respective sensing portion. A processor (104) is configured to process the measurement signal in response to an incident pressure stimulus (ΔP1, ΔP2) based on a predetermined sensitivity profile (504, 701) to determine an indication of the ambient pressure at the respective sensing portion.
G01L 11/02 - Mesure de la pression permanente, ou quasi permanente d'un fluide ou d'un matériau solide fluent par des moyens non prévus dans les groupes ou par des moyens optiques
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
G01R 33/032 - Mesure de la direction ou de l'intensité de champs magnétiques ou de flux magnétiques en utilisant des dispositifs magnéto-optiques, p.ex. par effet Faraday
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
G02B 6/44 - Structures mécaniques pour assurer la résistance à la traction et la protection externe des fibres, p.ex. câbles de transmission optique
This application relates to methods and apparatus for distributed fibre optic sensing and especially to the processing of signals derived from such sensing techniques to characterise events of interest. The application describes a method of distributed fibre optic sensing, comprising; performing distributed fibre optic sensing so as to generate at least one set of measurement signals from each of a plurality of sensing channels of an optical fibre (101) in response to at least one event of interest. For each set of measurement signals, processing the measurement signals from different sensing channels according to an association metric to determine whether any sensing channels are associated with one another and form at least one association matrix indicative of the sensing channels that are associated with one another. The method further comprising performing distributed fibre optic sensing to acquire a further set of measurement signals from said sensing channels in response to a further event of interest and processing said further set of measurement signals based on said at least one association matrix to characterise said further event of interest.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
B61L 25/02 - Indication ou enregistrement de la position ou de l'identité de véhicules ou de trains
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
This applications relates to methods and apparatus monitoring of subsea cables (100), for example subsea power or telecommunication cables, and in particular to determining a burial status for such cables. The method involves interrogating a sensing optical fibre (107) with an interrogator unit (108) to perform distributed fibre optic sensing. The sensing optical fibre (107) is deployed along the path of the subsea cable (100) and may, in some instances, form part of the subsea cable. A frequency spectrum of the respective measurement signal from at least one sensing portion of the sensing fibre (107), which corresponds to pressure variations (ΔP(t)) due to surface water waves (109) to determine a burial status. High frequency components of the pressure variation that are detected in any unburied section (106) are attenuated in buried sections (105).
G01R 31/08 - Localisation de défauts dans les câbles, les lignes de transmission ou les réseaux
G01L 1/24 - Mesure des forces ou des contraintes, en général en mesurant les variations des propriétés optiques du matériau quand il est soumis à une contrainte, p.ex. par l'analyse des contraintes par photo-élasticité
G01R 31/02 - Essai des appareils, des lignes ou des composants électriques pour y déceler la présence de courts-circuits, de discontinuités, de fuites ou de connexions incorrectes de lignes
H02G 9/02 - Installations de lignes ou de câbles électriques dans ou sur la terre ou sur l'eau tendus directement dans ou sur le sol, lit de rivière ou fond de mer; Leur recouvrement, p.ex. tuiles
This application relates to a fibre optic cable (104, 300) suitable for use with a distributed fibre optic sensor apparatus (106). The fibre optic cable includes at least one optical fibre (301)and a force transformer (304) mechanically coupled to the at least one optical fibre. The cable may also include at least one cladding later (302) and/or a compliant material (303). The cable may be surrounded by a jacket layer (306). The force transformer (304)is configured to transform transverse forces due to dimension changes of the cable arising from a temperature variation of the cable into longitudinal forces to counteract the longitudinal component of said dimension change over a tuned temperature range. In this way optical path length changes due to a change of temperature can be reduced or eliminated providing a cable which is insensitive to temperature.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
16.
DISTRIBUTED FIBRE OPTIC SENSING FOR IN-TRAIN FORCES MONITORING
This application relates to methods and apparatus for monitoring data obtained as a train (202) travels on along a rail track (201) to detect the occurrence and/or severity of any significant in-train forces, such as may be caused by heavy braking or excessive acceleration. The method involves taking a first data set corresponding to measurement signals from a plurality of channels of at least one fibre optic distributed acoustic sensor (202) having a sensing fibre (101) deployed to monitor at least part of the rail track. The first data set corresponds to measurement signals acquired as the train passes along the rail track. The method involves analysing the measurement signals to detect a first characteristic signature (402) which consists of a sequence of acoustic transients that appear to propagate rearwards along the train.
B61L 23/04 - Dispositifs de commande, d'avertissement ou autres dispositifs de sécurité le long de la voie ou entre les véhicules ou les trains pour contrôler l'état mécanique de la voie
B61L 27/00 - Systèmes centraux de commande du trafic ferroviaire; Commande côté voie; Systèmes de communication spécialement adaptés à cet effet
B61L 1/20 - Aménagements de sécurité pour empêcher ou signaler le mauvais fonctionnement du dispositif, p.ex. par perte de courant, par la foudre
B61L 1/06 - Dispositifs électriques associés à la voie actionnés par vibration du rail
This application relates to methods and apparatus for distributed fibre optic sensor and especially to Rayleigh based distributed fibre optic sensing that provides enhanced or additional information, such as information regarding large amplitude strains. A sensor has an interrogator (102) for interrogating a sensing optical fibre (101) to perform distributed acoustic sensing and provide a measurement signals from each of a plurality of channels corresponding to sensing portions of the sensing optical fibre. A processor (106, 107) analyses the measurement signals to detect a first characteristic signature (203), the first characteristic signature being a variation in the measurement signal from a plurality of channels that applies for a first channel and substantially all downstream channels and which occurs simultaneously on all such channels.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
18.
DETERMINING WELLBORE PROPERTIES WITH AN OPTIC FIBRE WHILE LOWERING A CASING
This application relates to method and apparatus for determining properties of a wellbore (201). The method involves attaching part of a sensing optical fibre (101) of a fibre optic cable (203) to a well casing (202) and inserting the well casing into the wellbore (201). The sensing fibre optic is connected to an interrogator unit (102) and distributed fibre optic sensing is performed on the sensing optical fibre as the well casing is being inserted into the wellbore to provide a measurement signal from each of a plurality of sensing portions of said sensing optical fibre. The measurement signal is indicative of disturbances affecting the sensing portions. A processor (107) analyses the measurement signals from sensing portions of the sensing optical fibre that has been inserted into the wellbore to determine wellbore properties.
E21B 43/10 - Mise en place de tubages, filtres ou crépines dans les puits
E21B 47/12 - Moyens pour la transmission de signaux de mesure ou signaux de commande du puits vers la surface, ou de la surface vers le puits, p.ex. pour la diagraphie pendant le forage
A temperature sensor for measuring temperature is described. The sensor comprises a fibre optic cable (104) comprising an optical fibre (102) and an interrogator unit (106) configured to interrogate the optical fibre with electromagnetic radiation, detect any radiation that is Rayleigh backscattered within the optical fibre and determine a measurement signal indicative of temperature changes for at least one longitudinal sensing portion of the optical fibre. A controllable thermal element, which may be a heating element, such as an electrically conducting element (108), is arranged along the length of the fibre optic cable (104) and in thermal communication with the fibre optic cable (104). A controller (110) is configured to generate a thermal variation in the controllable thermal element, e.g. by generating a time varying electric current in the electrically conducting element (108). An analyser (112) is configured to analyse the measurement signal, extract a thermal response signal corresponding to the thermal variation and compare the thermal response to a predetermined characteristic to determine the temperature of the fibre optic cable at said longitudinal sensing portion.
G01K 11/32 - Mesure de la température basée sur les variations physiques ou chimiques, n'entrant pas dans les groupes , , ou utilisant des changements dans la transmittance, la diffusion ou la luminescence dans les fibres optiques
20.
DISTRIBUTED FIBRE OPTIC SENSING FOR MONITORING RAIL NETWORKS
This application describes methods and apparatus for monitoring of rail networks using fibre optic distributed acoustic sensing (DAS), especially for condition monitoring. One method involves taking (902) a first data set corresponding to measurement signals from a plurality of channels of at least one fibre optic distributed acoustic sensor (100) having a sensing fibre (101) deployed to monitor at least part of the path of the rail network (201). The first data set corresponds to measurement signals acquired as a train (202) passed along a first monitored section of the rail network. The method involves identifying (903) a speed of the train through the first monitored section and dividing (904) the first data set into a plurality of time windows. Each time window contains a different subset of the first data set, with the measurement signal for each successive channel in a time window being delayed with respect to the previous channel by a time related to the identified train speed. For each time window, any appropriate time shift is identified (905) and applied (906) to the measurement signals for a channel so as to substantially align the measurement signals of the channels within the time window. The data from the time windows is then combined (907) after any time shifts have been applied to form an aligned first data set; and a characteristic train signal is derived (908) from the aligned first data set. The characteristic signal may be removed from the aligned first data set (1007) to leave remainder data. The characteristic trains signal and/or remainder data may be analysed for condition monitoring.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
B61L 1/16 - Dispositifs pour compter les essieux; Dispositifs pour compter les véhicules
B61L 25/02 - Indication ou enregistrement de la position ou de l'identité de véhicules ou de trains
This application describes methods and apparatus for tracking targets (105) in a fibre optic distributed acoustic sensing (DAS) network (100). The DAS network comprises a plurality of interrogator units (103) interrogating sensing fibres (102) deployed along paths of interest to provide DAS sensors. Targets are tracked (303) at each of a plurality of tracker nodes (106-1, 106-2, 106-3) of the DAS network, where each tracker node receives measurement signals from one or more DAS sensors and applies a tracking algorithm to track any targets in a respective tracker zone. Each tracker node maintains, for each target, a tracking dataset of target properties for tracking that target. The method involves identifying (307) when a first target in a first tracker zone of a first tracker node is approaching a second tracker zone of a second tracker node and supplying (308) from the first tracker node to the second tracker node a Target Descriptor for the first target. The second tracker node uses the Target Descriptor to track any entry of the first target into the second tracker zone.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
B61L 25/02 - Indication ou enregistrement de la position ou de l'identité de véhicules ou de trains
B61L 27/00 - Systèmes centraux de commande du trafic ferroviaire; Commande côté voie; Systèmes de communication spécialement adaptés à cet effet
This application relates to apparatus and methods for traffic monitoring, especially for monitoring of road traffic flow using fibre optic distributed acoustic sensing. The method involves performing distributed acoustic sensing (DAS) using a suitable interrogator unit (103) to provide a measurement signal from each of a plurality of sensing portions of a first length of a sensing optical fibre (102), where the first length of the sensing optical fibre runs alongside a road (101) having a plurality of lanes. The measurement signals from the sensing portions are processed to detect vehicles (104) travelling on the road and to determine at least one detected traffic flow property. The method further involves using a traffic flow model to relate the detected flow property to a modelled flow property, where the traffic flow model is configured to model vehicle detections that will be missed by the distributed acoustic sensing i.e. an indication of vehicles present on the road but not detected by the DAS sensor.
G08G 1/04 - Détection du mouvement du trafic pour le comptage ou la commande utilisant des détecteurs optiques ou ultrasonores
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
G08G 1/01 - Détection du mouvement du trafic pour le comptage ou la commande
G08G 1/015 - Détection du mouvement du trafic pour le comptage ou la commande avec des dispositions pour distinguer différents types de véhicules, p.ex. pour distinguer les automobiles des cycles
This application relates to methods and apparatus for distributed fibre optic sensing, especially distributed acoustic sensing (DAS). The sensor apparatus (300) has an optical generator (303, 305, 306) for repeatedly generating a first coded sequence of optical radiation to be launched into a sensing optical fibre (302). The first coded sequence is encoded according to a polylevel coding sequence (101) and has desired autocorrelation properties. A detector (311) detects optical radiation which has been Rayleigh backscattered from within the sensing optical fibre and a processor (301 c) processes the output of the detector. The processor processes the detector output in range bins and for each range bin correlating a detection signal derived from the detector output with the polylevel coding sequence at a time delay corresponding to that particular range bin. This provides a measurement signal indicative of environmental disturbances, such as incident acoustic/seismic signals, acting on a portion of the sensing fibre corresponding to that range bin.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
24.
MONITORING OF POWER CABLES WITH DISTRIBUTED FIBRE OPTIC SENSING
This application relates to methods and apparatus for monitoring power cables (100) carrying multiple AC phases to detect deformation of the power cable. A distributed fibre optic interrogator unit (302) is used to interrogate a sensing optical fibre (301) coupled to the power cable to provide a measurement signal from each of a plurality of longitudinal sensing portions of the sensing optical fibre. An analyser (602) is configured to analyse the measurements signals to detect a characteristic of an imbalance in magnetic fields. The characteristic may be a signal component with a characteristic frequency related to the power frequency and number of AC phases, the sensing optical fibre may be sensitised to magnetic fields and the characteristic frequency may be 2n times the power frequency where n is the number of phases, e.g. six times the power frequency for three phase AC.
G01R 31/02 - Essai des appareils, des lignes ou des composants électriques pour y déceler la présence de courts-circuits, de discontinuités, de fuites ou de connexions incorrectes de lignes
G01L 1/24 - Mesure des forces ou des contraintes, en général en mesurant les variations des propriétés optiques du matériau quand il est soumis à une contrainte, p.ex. par l'analyse des contraintes par photo-élasticité
G01R 31/08 - Localisation de défauts dans les câbles, les lignes de transmission ou les réseaux
H02G 1/00 - Méthodes ou appareils spécialement adaptés à l'installation, entretien, réparation, ou démontage des câbles ou lignes électriques
G01D 5/56 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens spécifiés dans plusieurs des groupes , , , et utilisant des moyens électriques ou magnétiques
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
25.
INTERFEROMETRIC MICROSEISMIC IMAGING METHODS AND APPARATUS
Methods and apparatus for interferometric seismic imaging and creation of a high- resolution three-dimensional seismic volume in proximity to a wellbore are described. In contrast to current methods that deliver positions of microseismic events using a small fraction of the microseismic wavefield, the present invention provides for the analysis of a full microseismic wavefield. In a preferred embodiment, the method includes creating a planar image slice and/or corridor between the location of one or more microseismic events and one or several sensor arrays to produce a multitude of azimuthally orientated planar image slices and/or corridors. The method further includes adding the planar image slice and/or corridor contributions to create a single three-dimensional volume for analysis and rendering.
G01V 1/28 - Traitement des données sismiques, p.ex. pour analyse, pour interprétation, pour correction
G01V 1/36 - Exécution de corrections statiques ou dynamiques sur des enregistrements, p.ex. correction de l'étalement; Etablissement d'une corrélation entre signaux sismiques; Elimination des effets produits par un excès d'énergie
This application relates to methods and apparatus for determining the location of a fault (204) in a power cable (100) of a power distribution network. The method involves monitoring at least one electrical parameter of the power distribution network to detect the occurrence of a fault in the power cable and determine at least one time window (twin) for the occurrence of the fault. The fault may be detected by detecting opening of a circuit breaker (205). The method involves analysing a first set of measurement signals is obtained by a distributed fibre optic sensor (302) having a sensing optical fibre (301) deployed along the path of the power cable. The first set of measurement signals comprise signals indicative of the extent of any disturbances on each of a plurality of longitudinal sensing portions of the sensing fibre over a known time period. The measurement signals are analysed based on said at least one time window for measurement signals (502) indicative of a fault in the power cable and the location of the fault in the power cable is identified based on the location of one or more longitudinal sensing portions of the sensing fibre giving rise to the measurement signals indicative of a fault in the power cable.
A fibre sensing apparatus (100) comprises an interrogation unit (104) to interrogate a sensing fibre with optical radiation, and to detect an optical signal returned from the fibre, and processing circuitry (114). A portion of the fibre may be excited with a test signal. The processing circuitry comprises an assessment module (115) to analyse the optical signal returned from the excited portion of fibre, and to determine at least one operational characteristic of the apparatus based on the detected optical signal.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
B61L 1/16 - Dispositifs pour compter les essieux; Dispositifs pour compter les véhicules
G01V 8/16 - Détection, p.ex. en utilisant des barrières de lumière en utilisant un émetteur et un récepteur en utilisant des fibres optiques
G01V 13/00 - Fabrication, étalonnage, nettoyage ou réparation des instruments ou dispositifs couverts par les groupes
28.
FIBRE OPTIC CABLE WITH TUNED TRANSVERSE SENSITIVITY
This application relates to a fibre optic cable structure suitable for use as a sensing fibre optic for distributed acoustic sensing and having an improved sensitivity to transverse pressure waves. The application describes a fibre optic cable (300) having a longitudinal cable axis and comprising at least one optical fibre (301). The cable also comprises a compliant core material (303) mechanically coupled to the optical fibre(s), possible via a buffer (302) such that a longitudinal force acting on the compliant core material induces a longitudinal strain in the optical fibre(s). At least one deformable strain transformer (304) is coupled to the compliant core material and configured such that a force acting on the strain transformer in a direction transverse to the cable axis results in a deformation of the strain transformer thereby applying a longitudinal force to the compliant core material.
G01L 11/02 - Mesure de la pression permanente, ou quasi permanente d'un fluide ou d'un matériau solide fluent par des moyens non prévus dans les groupes ou par des moyens optiques
G01L 1/24 - Mesure des forces ou des contraintes, en général en mesurant les variations des propriétés optiques du matériau quand il est soumis à une contrainte, p.ex. par l'analyse des contraintes par photo-élasticité
This application relates to methods and apparatus for the detection of anomalies in the wheelsets of rail vehicles, for instance for detection of defects such as wheel flats (303) of a wheel (301). The method using a distributed acoustic sensor (106) having a sensing optical fibre (104) deployed along at least part of a rail track (201) as a train (202) moves along that part of the track. The distributed acoustic sensor detects acoustic signals from a plurality of longitudinal sensing portions of the sensing optical fibre. A processor 108 analyses the acoustic signals to determine the train speed v. Having determined the train speed the processor also analyses the acoustic signals for a characteristic acoustic signal so as to detect an anomaly in a wheelset where the characteristic acoustic signal is based on the determined train speed. In particular the method may involve at least a first section of track where the train travels with a first speed v1 and a second section of track where the train travels with a second different speed v2 the characteristic acoustic signal may be a repetitive signal at a frequency that varies proportional to the train speed.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
B61K 9/12 - Mesure ou surveillance des jantes des roues
B61L 1/06 - Dispositifs électriques associés à la voie actionnés par vibration du rail
30.
MONITORING OF RESERVOIRS USING A FIBRE OPTIC DISTRIBUTED ACOUSTIC SENSOR
This application relates to the monitoring of reservoirs (201) within earth formations (202), for example hydrocarbon reservoirs or reservoirs for carbon sequestration, and especially to wide area seismic monitoring of such reservoirs using fibre optic distributed acoustic sensing (DAS) sensor. The DAS sensor has a sensing optical fibre (104) and an interrogator unit (106) for interrogating the sensing optical fibre to provide a plurality of sensing portions. The sensing optical fibre is deployed such that the optical fibre runs between a plurality of boreholes (204) and at each such borehole the fibre runs from the surface to at least a first depth in the borehole and back to the surface. The sensing fibre is preferably a continuous section of fibre without any splices. This allows a single interrogator unit to detect seismic signals in a plurality of boreholes reducing the number of sensors required compared to placing an individual sensor in each borehole, with consequent cost and maintenance savings. The applications also relates to methods of deployment and operation.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
E21B 47/12 - Moyens pour la transmission de signaux de mesure ou signaux de commande du puits vers la surface, ou de la surface vers le puits, p.ex. pour la diagraphie pendant le forage
G01V 1/42 - Séismologie; Prospection ou détection sismique ou acoustique spécialement adaptées au carottage en utilisant des générateurs dans un puits et des récepteurs dans un autre endroit ou vice versa
G01V 1/22 - Transmission des signaux sismiques aux appareils d'enregistrement ou de traitement
Methods and apparatus for determining fluid inflow to a well are described. In one example, a method comprise determining a first fluid flow velocity profile from slug tracking and determining a second fluid flow velocity profile from an estimate of fluid inflow at each of a plurality of perforations in a well. The first and second fluid flow velocity profiles are combined to provide a combined velocity profile. An indication of fluid inflow at least one perforation is derived from the combined velocity profile.
E21B 47/06 - Mesure de la température ou de la pression
E21B 47/12 - Moyens pour la transmission de signaux de mesure ou signaux de commande du puits vers la surface, ou de la surface vers le puits, p.ex. pour la diagraphie pendant le forage
Methods and apparatus for obtaining an indication of fluid inflow in a section of a gas well having multiple perforations through which fluids comprising gas and/or liquid enter the well are described. In an example, the temperature within the section of the gas well is monitored at a plurality of locations. The locations comprising (a) a first set of locations, at or near a perforation;and (b) a second set of locations at which the temperature is substantially independent of the effects of the inflow of gas at a perforation. An indication of temperature excursions at the locations is obtained and used to obtaining an indication of the inflow of fluids to the well by relating the indications of temperature excursions from the second set of locations to liquid inflow and relating the indications of temperature excursions from the first set of locations to liquid and gas inflow.
E21B 47/06 - Mesure de la température ou de la pression
E21B 47/12 - Moyens pour la transmission de signaux de mesure ou signaux de commande du puits vers la surface, ou de la surface vers le puits, p.ex. pour la diagraphie pendant le forage
This application describes methods and apparatus for distributed fibre optic sensing that allows for relatively rapid detection of temperature changes or other low frequency effects and/or calibration. The method involves performing a series of interrogations of an optical fibre(101). Each interrogation involves launching at least one interrogating pulse into the optical fibre; and detecting optical radiation which is backscattered from within the fibre –where the light from successive interrogations does not interfere. The method involves applying a predefined variation in frequency (Δf) between the pulses of different interrogations and determining any variation in backscatter intensity arising from such predefined variation in frequency. By varying the frequency of the interrogating pulses the operating point of a given channel is deliberately modulated. In the absence of any environmental stimulus this will lead to a repeated pattern of intensity variation, which could be used to determine the operating characteristics of the relevant channel. However any low frequency change will be detectable as a modulation on this intensity variation which can be detected.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
G01K 11/32 - Mesure de la température basée sur les variations physiques ou chimiques, n'entrant pas dans les groupes , , ou utilisant des changements dans la transmittance, la diffusion ou la luminescence dans les fibres optiques
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
This application describes methods and apparatus for distributed fibre optic sensing that reduce or compensate for the effects of laser phase noise. The method involves repeatedly interrogating an optical fibre (101), where each interrogation involves launching at least one interrogating pulse into the optical fibre; detecting optical radiation which is backscattered from within the fibre, and forming a measurement signal from a plurality of sensing portions of the fibre. The method involves forming a laser noise template based on the measurement signals within a frequency band of interest from a first set of said sensing portions; and applying a correction to the measurement signals from said plurality of sensing portions based on said laser noise template. The first set of sensing portions may be temperature and/or strain stable portion from an isolated section of fibre (301, 303) or may comprise a selected set of sensing portions, which may include substantially all the sensing portions, which are averaged to form the laser phase noise template. For a phase based DAS type sensor the laser phase noise template may simply be subtracted from the measurement signals. For an intensity based sensor it may be necessary to polarity align and normalise the signals of the first set before averaging and then determine a gain-time profile for each sensing portion prior to applying the correction.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
G01K 11/32 - Mesure de la température basée sur les variations physiques ou chimiques, n'entrant pas dans les groupes , , ou utilisant des changements dans la transmittance, la diffusion ou la luminescence dans les fibres optiques
A method of distributed fibre optic sensing is described. In an example, a series of interrogations are launched into an optical fibre, each interrogation comprising interrogating radiation in at least one pulse pair, wherein the pulses of a pulse pair are introduced to the optical fibre with a time interval therebetween. Radiation backscattered therefrom is sampled, so as to obtain at least one sample from each interrogation. Phase modulation in the samples is determined and components of the phase modulation which are below a threshold frequency are isolated. Such a method of sensing could be used, for example, to monitor changes in temperature of the optical fibre.
G01K 11/32 - Mesure de la température basée sur les variations physiques ou chimiques, n'entrant pas dans les groupes , , ou utilisant des changements dans la transmittance, la diffusion ou la luminescence dans les fibres optiques
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
G01M 3/00 - Examen de l'étanchéité des structures ou ouvrages vis-à-vis d'un fluide
G01M 3/04 - Examen de l'étanchéité des structures ou ouvrages vis-à-vis d'un fluide par utilisation d'un fluide ou en faisant le vide par détection de la présence du fluide à l'emplacement de la fuite
36.
FIBRE OPTIC DISTRIBUTED SENSING FOR PERIMETER MONITORING
This application relates to apparatus and methods for monitoring of a perimeter having a barrier (101) such as a chain-link fence. The system (100) has a sensing optical fibre (102) suitable for fibre optic distributed acoustic sensing (DAS) deployed along at least part of said perimeter, with at least part of the sensing optical fibre being buried, e.g. in the ground (104) in the vicinity of the barrier. In addition the sensing fibre is mechanically coupled to at least one vibration transmitting element (106) which is mechanically coupled to the barrier. In use the sensing fibre is interrogated by a DAS sensor unit (103). Being buried the sensing fibre is hidden from view, protected from sabotage and has good acoustic coupling to the ground, e.g. for detecting disturbances of the ground. The vibration transmitting elements ensure that any disturbance of the barrier, e.g. fence, itself is also well coupled to the sensing fibre and can be detected.
Method and apparatus for surveying the downhole environment in a steam stimulated well such as a Steam Assisted Gravity Draining well are described. One method comprises interrogating an optic fibre (104) arranged along the path of a well shaft (202, 204) within a steam stimulated well with optical radiation. At least one downhole steam pulse is generated and data gathered from the fibre (104) in response to the steam pulse is gathered and processed to provide an indication of the acoustic signals detected by at least one longitudinal sensing portion of the fibre (104). In some examples, the processed data can be used to determine at least one characteristic of the steam chamber (210).
E21B 43/24 - Procédés de récupération assistée pour l'extraction d'hydrocarbures utilisant la chaleur, p.ex. injection de vapeur
E21B 47/12 - Moyens pour la transmission de signaux de mesure ou signaux de commande du puits vers la surface, ou de la surface vers le puits, p.ex. pour la diagraphie pendant le forage
Methods and apparatus for surveillance of a downhole environment: the response of least one optical fibre to an acoustic impulse is sampled and processed to provide an indication of the acoustic signals detected by at least one longitudinal sensing portion of the fibre(s). The data comprises data indicative of at least one characteristic of the acoustic impulse and data indicative of the downhole environment. The data indicative of at least one characteristic of the acoustic impulse is used to interpret the data indicative of the downhole environment to provide an indication of at least one characteristic of the downhole environment. For example, the data indicative of at least one characteristic of the acoustic impulse may provide a 'signature' of the impulse, which may be used to deconvolve the data indicative of the downhole environment to provide an indication of at least one characteristic of the downhole environment.
G01V 11/00 - Prospection ou détection par des méthodes combinant des techniques spécifiées dans les groupes
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
E21B 47/12 - Moyens pour la transmission de signaux de mesure ou signaux de commande du puits vers la surface, ou de la surface vers le puits, p.ex. pour la diagraphie pendant le forage
E21B 47/10 - Localisation des fuites, intrusions ou mouvements du fluide
This application relates to fibre optic distributed acoustic sensing (DAS) applied using a sensing optical fibre (104) that is at least partly embedded in a cement structure (203) and addresses a problem of different acoustic sensitivities at different parts of the fibre (203). A method of producing an acoustic sensitivity profile is described which involves monitoring (501) temperature along the length of the optical fibre during curing of the surrounding cement structure. A temperature profile(301, 302) can then be generated (502) for the optical fibre based on said monitored temperature and used to generate (506) the acoustic sensitivity profile. The temperature profile indicates how well thermally coupled the fibre is to the surrounding cement, which also indicates how well acoustically coupled the fibre will be when the cement is cured. The sensitivity may be based on the rate of temperature change (303, 304) and/or magnitude of temperature change (T1, T2) during curing. The sensitivity profile can then be used to calibrate of adjust (604) measurement signals obtained using the optical fibre in a DAS sensor. The temperature during curing may be monitored using fibre optic distributed sensing such as DTS or DAS techniques.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
E21B 47/12 - Moyens pour la transmission de signaux de mesure ou signaux de commande du puits vers la surface, ou de la surface vers le puits, p.ex. pour la diagraphie pendant le forage
G01V 13/00 - Fabrication, étalonnage, nettoyage ou réparation des instruments ou dispositifs couverts par les groupes
G01V 1/22 - Transmission des signaux sismiques aux appareils d'enregistrement ou de traitement
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 fibre optic. The method also obtains a second temperature profile of the well by interrogating a second fibre optic to provide distributed sensing of temperature variations. Interrogating the second fibre optic comprises repeatedly launching interrogations of one or more pulses of coherent radiation into said second fibre optic, detecting any radiation which is Rayleigh backscattered from each interrogation and analysing 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.
E21B 43/24 - Procédés de récupération assistée pour l'extraction d'hydrocarbures utilisant la chaleur, p.ex. injection de vapeur
E21B 47/06 - Mesure de la température ou de la pression
E21B 47/12 - Moyens pour la transmission de signaux de mesure ou signaux de commande du puits vers la surface, ou de la surface vers le puits, p.ex. pour la diagraphie pendant le forage
This application describes method and apparatus for fibre optic distributed acoustic sensing (DAS) that allow for quantitative estimation of relatively large and continuous stimuli acting on the sensing fibre. An optical fibre (101) is interrogated with optical pulse and the Rayleigh backscatter detected to provide a DAS sensor. The method involves identifying a first stimulus acting on at least one sensing portion of the optical fibre, which results in an effective optical path length change within said sensing portion of at least the wavelength of the optical radiation. Such a path length change will result in signal wrapping leading to an observed variation (401) in backscatter intensity. The frequency of variation is detected and can be used to estimate the rate of change of path length. The method can be used to estimate strain rate and/or rate of change of temperature.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
The present application relates to road traffic monitoring to detect the number, speed and/or type of vehicles travelling on a road. Noise features (104) are deployed on, or formed in, the surface of a road (101). The noise feature (104) is arranged to generate a characteristic acoustic signature when traversed by the wheels of a vehicle (105) travelling within a lane of the road. A distributed acoustic sensor (102, 103) is deployed to detect occurrences of the characteristic acoustic signature. In some embodiments the noise element may comprise at least two distinct elements (104a, 104b), 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 categorise 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.
G08G 1/04 - Détection du mouvement du trafic pour le comptage ou la commande utilisant des détecteurs optiques ou ultrasonores
G08G 1/015 - Détection du mouvement du trafic pour le comptage ou la commande avec des dispositions pour distinguer différents types de véhicules, p.ex. pour distinguer les automobiles des cycles
G01G 19/03 - Appareils ou méthodes de pesée adaptés à des fins particulières non prévues dans les groupes pour peser des objets à roues ou roulants, p.ex. des véhicules pour peser pendant le mouvement
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
This application relates to fibre optic cable structures that are suitable for distributed acoustic sensing, and which may usefully be used for seismic monitoring/detection. The cable structures provide good sensitivity may further exhibit a directional sensitivity and thus can be used to discriminate between stimuli acting on the cable in different directions. One such fibre optic cable comprises a core structure (202, 203, 204) with an optical fibre wound around the periphery of the core structure. The core comprises a mass(203)which is moveable in a preferred direction within the cable such that movement of said mass in said preferred direction causes a change in length of the fibre wound around the periphery of the core.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
G01V 1/22 - Transmission des signaux sismiques aux appareils d'enregistrement ou de traitement
G01L 1/24 - Mesure des forces ou des contraintes, en général en mesurant les variations des propriétés optiques du matériau quand il est soumis à une contrainte, p.ex. par l'analyse des contraintes par photo-élasticité
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
This application relates to methods and apparatus for fibre optic sensing which can provide information about the environment in which the fibre optic is deployed. In particular the application relates to fibre optic based sensing of the mechanical impedance of the environment. The method comprises using an interrogator (201) to interrogate an optical fibre (104) which is coupled to a first element (202; 802) which is responsive to electromagnetic fields. In use a varying electric current (I), which may be an alternating current, is applied so as to induce a varying force (F) on said first element. The optical radiation backscattered from within the optical fibre is analysed to determine a measurement signal indicative of a variation in the backscattered radiation corresponding with said electric current applied. The first element may be a first conductor (202) and the varying current may be supplied to the first conductor, or to a second conductor (701). Alternatively the first element could be a magnetic element (802). By applying a variable force to the first element, and hence the optical fibre, the characteristics of the environment can be determined.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
G01D 5/26 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette
This application describes a radiation detector apparatus comprising: at least one optical fibre (104) suitable for distributed fibre optic acoustic/vibration sensing adjacent at least a first electrode (201) spaced apart from a second electrode (202) with a gas between the first and second electrodes.
G01T 1/18 - Mesure de l'intensité de radiation avec des aménagements de compteurs à tube, p.ex. des compteurs Geiger
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
This application describes methods and apparatus for monitoring flow at a given location downwell. The method of comprises performing fibre optic sensing on an optical fibre 204 deployed within the well 101. The optical fibre is attached to first tubing(201)that extends into the well to at least a first location(110a-c)at which it is wished to monitor inflow. The first tubing comprises at least one aperture (202a-c) having known properties at said first location. The first tubing is in fluid communication with flow tubing (107) that provides flow to/from the top (108) of the well. In use fluid therefore flows into the first tubing via the apertures (202a-c) which, having known properties, provide a calibrated response that can be detected by a fibre optic sensor unit (205).
E21B 47/10 - Localisation des fuites, intrusions ou mouvements du fluide
E21B 47/12 - Moyens pour la transmission de signaux de mesure ou signaux de commande du puits vers la surface, ou de la surface vers le puits, p.ex. pour la diagraphie pendant le forage
This application relates to conditions monitoring of structures forming part of a transport network, e.g. structural health monitoring of structures, especially tunnels. The method involves performing distributed acoustic sensing (DAS) on at least one optical fibre (104) deployed so as to monitor the structure (206). The acoustic response to movement of traffic (205) on the network in the vicinity of the structure is detected and analysed to detect the acoustic response (303, 304) of the structure. The acoustic response of the structure is then analysed to detect any change in condition. The method thus uses the normal movement of traffic on the network, e.g. trains on a rail network, to acoustic excite the structure and detects the resultant response. The method is particularly useful for condition monitoring of tunnels on a rail network.
G01M 5/00 - Examen de l'élasticité des structures ou ouvrages, p.ex. fléchissement de ponts ou d'ailes d'avions
B61L 23/04 - Dispositifs de commande, d'avertissement ou autres dispositifs de sécurité le long de la voie ou entre les véhicules ou les trains pour contrôler l'état mécanique de la voie
B61L 1/16 - Dispositifs pour compter les essieux; Dispositifs pour compter les véhicules
B61L 27/00 - Systèmes centraux de commande du trafic ferroviaire; Commande côté voie; Systèmes de communication spécialement adaptés à cet effet
This application describes methods and apparatus for remotely indicating a location of interest in an area, for instance the location of an event in the area. The method comprises positioning an acoustic source at the location of interest,activating the acoustic source to produce a predetermined acoustic output and performing distributed acoustic sensing on at least one optical fibre deployed at least partly in the area. The acoustic source thus acts as an acoustic marker which can be remotely detected by the distributed acoustic sensor. The acoustic signals detected by the distributed acoustic sensor are therefore analysed to detect said predetermined acoustic output and determine the location of the acoustic source. The method is particularly applicable to transport networks already provided with optical fibre along the length of the network and can be used to indicate the location of work parties or emergencies.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
This application describes method and apparatus for detecting train separation, where one or more railway cars/carriages (401)accidentally decouple from the rest of the train. The method involves performing distributed acoustic sensing on at least one optical fibre (104a, 104b) to provide a plurality of longitudinal acoustic sensor portions along the railway (201). The acoustic response is analysed to detect a signature indicative of a train separation. This may involve detecting acoustic events (302, 303) associated with different parts of the train and detecting when the separation between the two events exceeds a threshold amount. The method may identify the front of the train and the rear of the train and detect when the distance between the front and rear changes by more than a threshold amount and/or sounds associated with wheelsets passing track features (402) may be used to determine the intervals(T3, T4) between wheelsets of adjacent cars and determine when the interval exceeds a threshold amount. The threshold may be based on the interval (T2) between wheelsets of the same car passing the track feature.
The application describes methods and apparatus for control of transport networks, especially rail networks. The method involves monitoring at least part of the rail network(202, 203,204) by performing distributed acoustic sensing on one or more optical fibres(104a, 104b, 104c) deployed along the path of the network to provide a plurality of acoustic sensing portions. The signals detected by the plurality of acoustic sensing portions are analysed to detect acoustic signals associated with trains(205) moving on the network. The signals are analysed to identifying the front and rear of said trains and to track the movement of trains on the network. Indentifying the front and rear of a train may involve identifying the start/end (302, 303) of a continuous acoustic signal generated by the train and/or identifying characteristic signatures generated by the wheelsets of the train. The method may be used to provide moving block signalling.
B61L 1/14 - Dispositifs pour indiquer le passage de l'arrière d'un véhicule ou de la queue d'un train
B61L 27/00 - Systèmes centraux de commande du trafic ferroviaire; Commande côté voie; Systèmes de communication spécialement adaptés à cet effet
B61L 1/16 - Dispositifs pour compter les essieux; Dispositifs pour compter les véhicules
B61L 23/04 - Dispositifs de commande, d'avertissement ou autres dispositifs de sécurité le long de la voie ou entre les véhicules ou les trains pour contrôler l'état mécanique de la voie
The application describes methods and apparatus for seismic monitoring using fibre optic distributed acoustic sensing (DAS). The method involves interrogating a first optical fibre (102) deployed in an area of interest to provide a distributed acoustic sensor comprising a plurality of longitudinal sensing portions of fibre and also monitoring at least one geophone (107) deployed in the area of interest. The signal from the at least one geophone is analysed to detect an event of interest (105). If an event of interest is detected the data from the distributed acoustic sensor acquired during said event of interest is recorded. Th geophone may be co-located with part of the sensing fibre and in some embodiments may be integrated (307) with the sensing fibre.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
G01V 1/22 - Transmission des signaux sismiques aux appareils d'enregistrement ou de traitement
G01V 1/44 - Séismologie; Prospection ou détection sismique ou acoustique spécialement adaptées au carottage en utilisant des générateurs et des récepteurs situés dans le même puits
G01V 1/28 - Traitement des données sismiques, p.ex. pour analyse, pour interprétation, pour correction
The present application described methods an apparatus for locating and/or monitoring subsea cables (101) having an optical fibre (105) deployed along its length. The optical fibre (105) is connected to a distributed acoustic sensing (DAS) interrogator unit to interrogate the optical fibre to provide a fibre optic DAS sensor. To locate the cable an acoustic stimulus is transmitted into the water from one or more known locations. The time of arrival of an acoustic signal matching the stimulus at the sensing portions of the DAS fibre can be detected and used to determine information about the location of those sensing portions to the known location. The DAS signals returns can also be monitored under ambient conditions to detect any signals indicative of likely damage to the cable.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
G02B 6/50 - Installation souterraine ou sous l'eau; Installation à travers des tubes, des conduits ou des canalisations
G10K 11/00 - Procédés ou dispositifs pour transmettre, conduire ou diriger le son en général; Procédés ou dispositifs de protection contre le bruit ou les autres ondes acoustiques ou pour amortir ceux-ci, en général
H02G 1/10 - Méthodes ou appareils spécialement adaptés à l'installation, entretien, réparation, ou démontage des câbles ou lignes électriques pour poser les câbles, p.ex. appareils de pose sur véhicule dans ou sur l'eau
G01V 1/38 - Séismologie; Prospection ou détection sismique ou acoustique spécialement adaptées aux zones recouvertes d'eau
This application describes methods and apparatus for monitoring flow of fluids within conduits using fibre 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 fibre (104) deployed along the path of the conduit to provide a DAS sensor; and analysing the acoustic signals detected by a plurality of channels of the DAS sensor to determine at least one flow characteristic. Analysing the acoustic signal comprises identifying reflections (804) of said acoustic stimulus caused by the fluid within the conduit and analysing said reflections to determine any Doppler shift (Δf).
E21B 47/10 - Localisation des fuites, intrusions ou mouvements du fluide
G01F 1/66 - Mesure du débit volumétrique ou du débit massique d'un fluide ou d'un matériau solide fluent, dans laquelle le fluide passe à travers un compteur par un écoulement continu en mesurant la fréquence, le déphasage, le temps de propagation d'ondes électromagnétiques ou d'autres types d'ondes, p.ex. en utilisant des débitmètres à ultrasons
G01F 1/704 - Mesure du débit volumétrique ou du débit massique d'un fluide ou d'un matériau solide fluent, dans laquelle le fluide passe à travers un compteur par un écoulement continu utilisant des zones marquées ou non homogènes de l’écoulement de fluide, p.ex. des variations statistiques d'un paramètre du fluide
A method and apparatus for determining the relative orientation of objects downwell, and especially to determining perforator orientation, involves varying the orientation of an object, such as a perforator gun (302) in the wellbore (202) and activating at least one directional acoustic source (402a-c). Each directional acoustic source is fixed in a predetermined location to the object and transmits an acoustic signal preferentially in a known direction. The directional acoustic sources are activated so as to generate sound in a plurality of different orientations of said object. An optical fibre (104) is interrogated to provide distributed acoustic sensing in the vicinity of the object; and the acoustic signals detected by the optical fibre are analysed to deter¬ mine the orientation of the at least one directional acoustic source relative to the optical fibre, for instance by looking at the relative intensity in the different orientations.
E21B 43/119 - Perforateurs; Perméators - Parties constitutives, p.ex. pour localiser l'emplacement ou la direction de la perforation
E21B 47/12 - Moyens pour la transmission de signaux de mesure ou signaux de commande du puits vers la surface, ou de la surface vers le puits, p.ex. pour la diagraphie pendant le forage
E21B 47/024 - Détermination de l'inclinaison ou de la direction des dispositifs dans le trou de forage
E21B 47/022 - Détermination de l'inclinaison ou de la direction du trou de forage, p.ex. à l'aide de géomagnétisme
G01V 11/00 - Prospection ou détection par des méthodes combinant des techniques spécifiées dans les groupes
G01V 1/44 - Séismologie; Prospection ou détection sismique ou acoustique spécialement adaptées au carottage en utilisant des générateurs et des récepteurs situés dans le même puits
There is provided a distributed sensor, comprising a length of optic fibre; an interrogator unit having a detector arranged to detect light from the optic fibre, wherein the interrogator is arranged to provide distributed sensing on the optic fibre and wherein an optical path is defined between the optic fibre and the interrogator detector; a sampler coupled to the optic fibre and arranged to obtain a sample of light from the optical path of the optic fibre; a threshold detector arranged to detect the intensity of the sampled light and determine whether the intensity of the sampled light is above a threshold value; and an optical attenuator provided in the optical path and arranged to attenuate light propagating along the optical path when the intensity of the sampled light is above the threshold value. By attenuating light in the optical path if it is above a threshold value, the sensitive detector in the interrogator unit can be protected.
H04B 10/67 - Dispositions optiques dans le récepteur
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
The present invention relates to a portal monitoring system that uses distributed sensing to detect metallic objects passing through the portal. The system comprises a length of fibre optic (102) comprising an optical fibre(106)mechanically coupled to a material(108)whose physical characteristics vary dependent on the applied magnetic field. The fibre optic (102) is arranged in the vicinity of a portal(200) and a fibre optic interrogator(104) is adapted to provide distributed sensing on the optical fibre to provide measurement data from a plurality of contiguous portions of said optical fibre at each of a plurality of times. A data analyser processes the measurement data to detect signals characteristic of a disturbance in the magnetic field along the optical fibre. The system of the present invention is able to monitor multiple people passing though a portal at the same time and provide an indication of the location of metallic objects within the portal.
G01V 3/08 - Prospection ou détection électrique ou magnétique; Mesure des caractéristiques du champ magnétique de la terre, p.ex. de la déclinaison ou de la déviation fonctionnant au moyen de champs magnétiques ou électriques produits ou modifiés par les objets ou les structures géologiques, ou par les dispositifs de détection
57.
SEISMIC GEOPHYSICAL SURVEYING USING A FIBRE OPTIC DISTRIBUTED SENSING APPARATUS
The present invention relates to an apparatus for use in geophysical surveying. Geophysical surveying typically involves stimulating an area of interest with a seismic source (204)and detecting the response in a sensor array. The application describes a fibre optic distributed sensing apparatus having a source(112)of electromagnetic radiation for repeatedly launching interrogating electromagnetic radiation into an optic fibre(104) deployed in said of area interest,a sampling detector (116) for sampling radiation back- scattered from the fibre; and a processor(108)arranged to process the back-scattered radiation to provide, for each of a plurality of longitudinal sensing portions of optic fibre, an indication of any incident acoustic signals affecting that sensing portion. The sampling detector is arranged to acquire a plurality of diversity samples for each said longitudinal sensing portion. The processor is configured process the diversity samples in diversity channels to determine a measurement signal indicative of any acoustic disturbance; correlate the measurement signal from each channel with a signal indicative of the seismic stimulus applied; and combine the correlated measurement signals to provide an overall measurement signal for the longitudinal sensing portion. The processor may apply a quality metric to the correlated data before performing the combination based on the quality metric. By correlating the individual diversity channels with the stimulus signal prior to performing the analysis of the measurement signal for a particular longitudinal section of optic fibre, the signal to noise ratio can be improved.
This application relates to methods and apparatus for monitoring of conduits, especially oil or gas pipelines, as an object such as pipeline pig moves within the conduit. The method comprises monitoring at least part of a conduit(206) using a fibre optic(202) distributed acoustic sensor (204) as the object (208) passes along the conduit. The acoustic signals detected from at least one sensing location (203) as the object moves along the conduit are analysed so as to discriminate acoustic signals received at said sensing location from different locations. The method allows the contributions to the acoustic signal at a given sensing portion from different locations to be separately identified, and can allow the detection of the location of acoustic sources along the conduit even if the source is outside the section of conduit which is monitored. The method provides a method of leak detection that can extend the monitoring of the pipeline beyond the location of the optical fibre.
G01M 5/00 - Examen de l'élasticité des structures ou ouvrages, p.ex. fléchissement de ponts ou d'ailes d'avions
G01M 3/00 - Examen de l'étanchéité des structures ou ouvrages vis-à-vis d'un fluide
G01M 3/24 - Examen de l'étanchéité des structures ou ouvrages vis-à-vis d'un fluide par utilisation d'un fluide ou en faisant le vide par détection de la présence du fluide à l'emplacement de la fuite en utilisant des vibrations infrasonores, sonores ou ultrasonores
G01M 3/38 - Examen de l'étanchéité des structures ou ouvrages vis-à-vis d'un fluide par utilisation de la lumière
F17D 5/00 - Protection ou surveillance des installations
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
The present invention relates to a method of integrity monitoring of a conduit. An optic fibre is provided optic fibre along the path of the conduit, and a fluid in the conduit is pressurized and depressurized. The optic fibre is interrogated to provide a distributed acoustic sensor, and data is sampled from a plurality of longitudinal portions of the fibre during the pressurizing and depressurizing. The data is processed to detect a signal characteristic of the integrity of the conduit.
G01M 3/24 - Examen de l'étanchéité des structures ou ouvrages vis-à-vis d'un fluide par utilisation d'un fluide ou en faisant le vide par détection de la présence du fluide à l'emplacement de la fuite en utilisant des vibrations infrasonores, sonores ou ultrasonores
G01M 5/00 - Examen de l'élasticité des structures ou ouvrages, p.ex. fléchissement de ponts ou d'ailes d'avions
E21B 47/00 - Relevés dans les trous de forage ou dans les puits
E21B 47/10 - Localisation des fuites, intrusions ou mouvements du fluide
The application describes methods and apparatus for distributed fibre sensing, especially distributed acoustic/strain sensing. The method involves launching interrogating radiation in to an optical fibre and sampling radiation backscattered from within said fibre at a rate so as to acquire a plurality of samples corresponding to each sensing portion of interest. The plurality of samples are divided into separate processing channels and processed to determine a phase value for that channel. A quality metric is then applied to the processed phase data and the data combined to provide an overall phase value for the sensing portion based on the quality metric. The quality metric may be a measure of the degree of similarity of the processed data from the channels. The interrogating radiation may comprise two relatively narrow pulses separated by a relatively wide gap and the sampling rate may be set such that a plurality of substantially independent diversity samples are acquired.
G01D 1/00 - Dispositions pour la mesure donnant des résultats autres que la valeur instantanée d'une variable, d'application générale
G01D 1/02 - Dispositions pour la mesure donnant des résultats autres que la valeur instantanée d'une variable, d'application générale donnant des valeurs moyennes, p.ex. des valeurs efficaces
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
The application describes methods and apparatus for distributed fibre sensing, especially distributed acoustic/strain sensing. The method involves launching at least first and second pulse pairs into an optical fibre, the first and second pulse pairs having the same frequency configuration as one another and being generated such that the phase relationship of the pulses of the first pulse pair has a predetermined relative phase difference to the phase relationship of the pulses of the second pulse pair. In one embodiment there is a frequency difference between the pulses in a pulse pair which is related to the launch rate of the pulse pairs. In another embodiment the phase difference between the pulses in a pair is varied between successive launches. In this way an analytic version of the backscatter interference signal can be generated within the baseband of the sensor.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
62.
SUBSURFACE MONITORING USING DISTRIBUTED ACOUSTIC SENSORS
This application relates to methods and apparatus for geophysical monitoring within wellbores. The method involves interrogating an optical fibre (106) deployed along substantially the entire length of the wellbore (201) to provide distributed acoustic sensing and detecting the acoustic response from substantially the entire length of the wellbore in response to a seismic stimulus (204). The acoustic returns from individual sensing portions of the optical fibre can be processed to provide a profile such as a vertical seismic profile (VSP). An acoustic response from the entire length of the well can be recorded using a single shot of the seismic source.
G01V 1/42 - Séismologie; Prospection ou détection sismique ou acoustique spécialement adaptées au carottage en utilisant des générateurs dans un puits et des récepteurs dans un autre endroit ou vice versa
G01V 1/22 - Transmission des signaux sismiques aux appareils d'enregistrement ou de traitement
The present invention relates to a method of monitoring a fluid carrying conduit, comprising interrogating an optic fibre positioned along the path of said conduit to provide distributed acoustic sensing, measuring by distributed acoustic sensing the acoustic signal at each of a plurality of discrete longitudinal sensing portions along the length of the optic fibre, to monitor the optic fibre for the presence of a first characteristic signal, the first characteristic signal being indicative of ground heave the vicinity of the optic fibre, and determining that a failure has occurred in said conduit when a first characteristic signal is measured in the distributed acoustic sensing.
G01M 3/24 - Examen de l'étanchéité des structures ou ouvrages vis-à-vis d'un fluide par utilisation d'un fluide ou en faisant le vide par détection de la présence du fluide à l'emplacement de la fuite en utilisant des vibrations infrasonores, sonores ou ultrasonores
G01M 3/38 - Examen de l'étanchéité des structures ou ouvrages vis-à-vis d'un fluide par utilisation de la lumière
The application describes techniques for monitoring the rate of flow of fluid in a conduit (205) using fibre optic distributed acoustic sensing which are especially applicable to flow in oil and gas wells. The techniques also allow for calibration of the position of the channels of a fibre optic distributed acoustic sensor arranged along a fluid carrying conduit. The techniques comprise introducing a first acoustic stimulus (303) travelling in one direction and a second acoustic stimulus (304) travelling in the opposite direction. Flow of the fluid (v) results in a difference in the propagation velocity of the two acoustic stimuli. The first and second acoustic stimuli create a standing wave and the beat effect due to the flow induced wavelength variation is detected and used to determine flow rate. The acoustic stimulus may be introduced to travel through the conduit to provide the first stimulus and to reflect from the end of the conduit and travel back as the second acoustic stimulus.
G01F 1/00 - Mesure du débit volumétrique ou du débit massique d'un fluide ou d'un matériau solide fluent, dans laquelle le fluide passe à travers un compteur par un écoulement continu
G01F 1/66 - Mesure du débit volumétrique ou du débit massique d'un fluide ou d'un matériau solide fluent, dans laquelle le fluide passe à travers un compteur par un écoulement continu en mesurant la fréquence, le déphasage, le temps de propagation d'ondes électromagnétiques ou d'autres types d'ondes, p.ex. en utilisant des débitmètres à ultrasons
G01P 5/24 - Mesure de la vitesse des fluides, p.ex. d'un courant atmosphérique; Mesure de la vitesse de corps, p.ex. navires, aéronefs, par rapport à des fluides en mesurant l'influence directe du courant de fluide sur les propriétés d'une onde acoustique de détection
This application describes methods and apparatus for distributed acoustic sensing providing enhanced sensitivity for certain acoustic signals. The method uses a fibre optic distributed acoustic sensing (DAS) apparatus (106) to detect acoustic signals wherein the fibre optic distributed acoustic sensor comprises at least one optical fibre (104) deployed in an area of interest (204) such that at least one section of said optical fibre is deployed to monitor the acoustic response of a cavity (206) to incident acoustic signals. The cavity is dimensioned such that the cavity resonates at a desired frequency and thus the relevant sensing portions of the DAS sensor show an enhanced response to acoustic signals which excite resonance in the cavity. The optical fibre (104) may be deployed to run through said cavity.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
This application describes methods and apparatus for fibre optic distributed acoustic sensing (DAS) where microstructured fibre (202), such as holey fibre or photonic crystal fibre is used as the sensing fibre (104). The microstructured fibre is configured so to provide at least one of enhanced sensitivity to a given incident acoustic signal; an enhanced non-linear optical power threshold and directional sensitivity. By configuring the microstructuped fibre to be more compliant than an equivalent solid fibre and/or provide a large refractive index variation in response to applied strain, the response to a given acoustic stimulus may be larger than for the equivalent fibre, Providing a hollow core may allow higher optical powers and by providing a directionality to microstructured (304) allows the fibre to be used in a DAS system with a directional response.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
This application relates to methods and apparatus for seismic surveying using optical fibre distributed acoustic sensing (DAS). The method involves using a fibre optic distributed acoustic sensor to detect seismic signals. The fibre optic distributed acoustic sensor comprises an interrogator (106) arranged to interrogate at least one optical fibre (104) buried in the ground (204) in the area of interest. The method involves stimulating the ground using a seismic source (201 ) and detecting the seismic signals, for example reflected from various rock strata (202, 203).
This application relates to methods and apparatus for monitoring hydraulic fracturing in well formation and fracture characterisation using distributed acoustic sensing (DAS). The method involves interrogating a optic fibre (102) arranged down the path of a bore hole (106) to provide a distributed acoustic sensor and also monitoring flow properties of fracturing fluid pumped (114) into the well. 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.
This application relates to a fibre optic cable which is adapted for use in a distributed fibre optic sensor such as a distributed acoustic sensor. The cable (201) comprises at least one optical fibre (208) and a shear thickening non-Newtonian fluid (202) disposed within the cable. The presence of a shear thickening fluid in the cable means that in response to a mechanical vibration or strain such as due to an incident acoustic wave the apparent viscosity of the non-Newtonian fluid will increase. In effect the cable will stiffen which will increase the strain on the optical fibre used for sensing, and thus increase the sensitivity of the cable to incident signals. The non-Newtonian fluid may be a dilatant material and/or a rheopectic material and may comprise comprises a plurality of particles disposed within a liquid.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
There is provided a system (100) for magnetic field detection, comprising a fibre optic interrogator (104) adapted to interrogate a first length of optical fibre (102) with interrogating radiation, detect radiation backscattered from said optical fibre and analyse said detected radiation to provide distributed sensing indicative of mechanical disturbances of said optical, wherein the optic fibre is mechanically coupled to a material whose dimensions vary dependant on applied magnetic field. Changes in dimensions of the optic fibre as can be detected by virtue of changes in back-scattering of light from said fibre using the principles of fibre optic distributed acoustic sensing.
G01R 33/032 - Mesure de la direction ou de l'intensité de champs magnétiques ou de flux magnétiques en utilisant des dispositifs magnéto-optiques, p.ex. par effet Faraday
An apparatus and method for detecting gunfire is provided which uses distributed acoustic sensing to provide the gunfire detection. The method comprises interrogating an optical fibre with electromagnetic radiation to provide a distributed acoustic sensor comprising a plurality of sensing portions of the optical fibre, and analysing a measurement signal from said sensing portions to detect gunfire events. A gunfire event will typically be relatively intense but of short duration and affect multiple sensing channels. The method may detect a characteristic 602 of a muzzle blast and/or a characteristic 601 of pressure wave from a supersonic round and may determine the location of the gunfire and the location at which the round crosses the sensor.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
A system for moving object (402) detection is provided, the system comprising a fibre optic interrogator (106) adapted to provide distributed acoustic sensing on a optic fibre (104), for example arranged along a border. The measurement signals from each of a plurality of sensing portions (404, 406, 408, 410, 412) of said fibre are analysed 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, t2, t3, t4, t5) 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.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
A method of interrogating a test fibre to provide distributed acoustic sensing along an optic fibre, wherein pairs of temporally overlapped pulses are introduced into the fibre. Return signals are detected and demodulated to provide phase information representative of disturbances along the fibre. The demodulation effectively separates out the overlapped portion and may comprise separating a constant phase component from a modulated phase component. Alternatively demodulating may comprise differentiating said output and integrating said differentiated output to produce a reconstructed signal.
The invention relates to a distributed fibre optic sensor (104, 106) having a first spatial resolution (301, 303) and a second, different, spatial resolution (302, 304). The sensor, which may be a distributed acoustic sensor, has an optical source (112) configured to interrogate an optical fibre (104) with optical radiation and a detector (116) configured to detected optical radiation back-scattered from within the fibre. A processor (108) is configured to process the detected back-scatter radiation to provide a plurality of longitudinal sensing portions of fibre. The optical source and processor are adapted to provide the first and second spatial resolutions, for instance by changing the duration and /or separation of the optical pulses and analysis bins. The first and second spatial resolutions may be provided sequentially or simultaneously and the spatial resolution used may be varied as part of a default pattern or in response to a detection event.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
G08B 13/186 - Déclenchement influencé par la chaleur, la lumière, ou les radiations de longueur d'onde plus courte; Déclenchement par introduction de sources de chaleur, de lumière, ou de radiations de longueur d'onde plus courte utilisant des systèmes détecteurs de radiations actifs par interruption d'un faisceau ou d'une barrière de radiations utilisant des guides de lumière, p.ex. fibres optiques
A method of distributed fibre optic sensing is described in which an optical fibre (104) is interrogated with electromagnetic radiation; back-scattered radiation is detected; and the returns are processed to provide a measurement signal (310) for each of a plurality of longitudinal sensing portions of the optical fibre. The method comprises analysing the measurement signals of a first subset of longitudinal sensing portions to provide a first zone (306a) having a first sensing function and analysing the measurement signals of at least a second subset of longitudinal sensing portions to provide at least a second zone (306b) having a second, different, sensing function. The different sensing functions may include detecting different events of interest. In some embodiments the geometry of the fibre may provide different sensing zones (406a, 406b).
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
G08B 13/186 - Déclenchement influencé par la chaleur, la lumière, ou les radiations de longueur d'onde plus courte; Déclenchement par introduction de sources de chaleur, de lumière, ou de radiations de longueur d'onde plus courte utilisant des systèmes détecteurs de radiations actifs par interruption d'un faisceau ou d'une barrière de radiations utilisant des guides de lumière, p.ex. fibres optiques
Techniques for determining lateral offset of the source of an acoustic disturbance in a distributed acoustic fibre optic sensor are described. The sensor comprises an optical source (112) for interrogating an optical fibre (104) and a detector (116) and processor (108) arranged to detect any backscattered radiation and determine a measurement signal for a plurality of discrete longitudinal sensing portions of the optical fibre. 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 fibre 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 fibre. The geometry of the fibre may be arranged to ensure that any positional ambiguity can be resolved and the use of multiple fibres (501, 502) is disclosed.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
G01S 15/88 - Systèmes sonar, spécialement adaptés à des applications spécifiques
G08B 13/00 - Alarmes contre les cambrioleurs, les voleurs ou tous intrus
Fibre optic cables with improved performance for use in distributed sensing, for instance in distributed acoustic sensors, are disclosed. In one embodiment a fibre optic cable (210) comprises a core (208) and cladding (206) disposed within a buffer material (202) and surrounded by a jacket (204) and arranged so that the core is offset from the centre of the cable. By offsetting the core from the centre of the jacket any bending effects on the core can be maximised compared with the core being located at the centre of the cable.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
G01L 1/24 - Mesure des forces ou des contraintes, en général en mesurant les variations des propriétés optiques du matériau quand il est soumis à une contrainte, p.ex. par l'analyse des contraintes par photo-élasticité
G01L 11/02 - Mesure de la pression permanente, ou quasi permanente d'un fluide ou d'un matériau solide fluent par des moyens non prévus dans les groupes ou par des moyens optiques
H04B 10/08 - Equipement de surveillance, d'essai ou de mesure des défauts
G02B 6/036 - Fibres optiques avec revêtement le noyau ou le revêtement comprenant des couches multiples
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