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 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
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 11/3206 - 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 en des endroits distincts de la fibre, p.ex. utilisant la diffusion de Bragg
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 27/70 - Systèmes centraux de commande du trafic ferroviaire; Commande côté voie; Systèmes de communication spécialement adaptés à cet effet - Détails des communications côté voie
B61L 25/02 - Indication ou enregistrement de la position ou de l'identité de véhicules ou de trains
5.
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.
G01B 7/16 - Dispositions pour la mesure caractérisées par l'utilisation de techniques électriques ou magnétiques pour mesurer les déformations dans un solide, p.ex. au moyen d'une jauge de contrainte à résistance
H02G 9/00 - Installations de lignes ou de câbles électriques dans ou sur la terre ou sur l'eau
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.
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.
G01B 11/16 - Dispositions pour la mesure caractérisées par l'utilisation de techniques optiques pour mesurer la déformation dans un solide, p.ex. indicateur optique de déformation
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
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 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.
B61K 9/12 - Mesure ou surveillance des jantes des roues
B61L 1/06 - Dispositifs électriques associés à la voie actionnés par vibration du rail
G01P 3/02 - Dispositifs caractérisés par l'emploi de moyens mécaniques
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 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.
G01D 5/32 - 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
E21B 47/135 - 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 par énergie électromagnétique, p.ex. gammes de fréquence radio utilisant des ondes lumineuses, p.ex. ondes infrarouges ou ultraviolettes
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
G01M 3/38 - Examen de l'étanchéité des structures ou ouvrages vis-à-vis d'un fluide par utilisation de la lumière
81800838 ABSTRACT Methods and apparatus for determining fluid inflow to a well are described. In one example, a method comprises 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 at least one perforation is derived from the combined velocity profile. Date Recue/Date Received 2021-07-27
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.
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.
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 47/14 - 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 utilisant des ondes acoustiques
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 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
81784918 ABSTRACT This application relates to fibre optic sensing which can provide information about the environment in which the fibre optic is deployed, in particular the mechanical impedance. An interrogator is used to interrogate an optical fibre which is coupled to a first element which is responsive to electromagnetic fields. In use a varying, e.g. alternating, electric current, is applied so as to induce a varying force on said first element. The optical radiation backscattered from within the optical fibre is analysed to determine a variation corresponding with said electric current applied. The first element may be a first conductor and the varying current may be supplied to the first conductor, or to a second conductor. Alternatively the first element could be a magnetic element. By applying a variable force to the first element, and hence the optical fibre, the characteristics of the environment can be determined. Date Recue/Date Received 2020-07-31
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 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 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
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 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
G01V 1/38 - Séismologie; Prospection ou détection sismique ou acoustique spécialement adaptées aux zones recouvertes d'eau
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
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 47/022 - Détermination de l'inclinaison ou de la direction du trou de forage, p.ex. à l'aide de géomagnétisme
E21B 47/024 - Détermination de l'inclinaison ou de la direction des dispositifs dans le trou de forage
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 1/44 - 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.
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
23.
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
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
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
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
E21B 47/00 - Relevés dans les trous de forage ou dans les puits
E21B 47/10 - Localisation des fuites, intrusions ou mouvements du fluide
G01M 5/00 - Examen de l'élasticité des structures ou ouvrages, p.ex. fléchissement de ponts ou d'ailes d'avions
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
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
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.
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
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
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
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
G01D 5/32 - 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
A method of distributed acoustic sensing (DAS) whereby the derivative or rate of change of a signal backscatted from a fibre is measured. The change, or derivative of the phase measured in this way has a much smaller amplitude than the signal itself if the difference between the two times at which the signal is measured is much less than the period of the signal being measured, resulting in lower sensitivity. Frequency shifts can be applied to temporally displaced return signals to compare the rate of change, for example by employing an output interferometer arranged to modulate the signal in each arm by a different frequency shift.
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
35.
WELL MONITORING BY MEANS OF DISTRIBUTED SENSING MEANS
Methods and apparatus for downhole monitoring are provided by interrogating an unmodified optic fibre (102) ar-ranged along the path of a well bore (106) to provide a distributed acoustic sensor and sampling data gathered from a plurality of contiguous sensing portions of the fibre. The sampled data is processed to determine one or more well bore parameters. The well bore parameters may comprise a well condition profile, and may be obtained in response to an acoustic stimulus.
This application relates to methods and apparatus for monitoring hydraulic fracturing during oil/gas well forma-tion. A fibre optic cable (102) deployed down a well bore (106), which may be the well bore in which fracturing is performed, is interrogated to provide a distributed acoustic sensor. Data is sampled from at least one longitudinal sensing portion of the fibre and processed to provide at least fracturing characteristic. The fracturing characteristic may comprise the characteristics of high frequency transients indicative of fracturing events (606). The intensity, frequency, duration and signal evolution of the transients may be monitored to provide the fracturing characteristic. Additionally or alternatively the fracturing characteristic may comprise the longer term acoustic noise generated by fracture fluid flow to the fracture sites. The intensity and frequency of the noise may be analysed to determine the fracturing characteristic. The method allows real- time control of the fracturing process.
E21B 43/26 - Procédés pour activer la production par formation de crevasses ou de fractures
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
37.
WELL MONITORING BY MEANS OF DISTRIBUTED SENSING MEANS
This application describes methods and apparatus for downhole monitoring in real-time. The method involves interrogating an unmodified optic fibre (102) arranged along the path of a well bore (106) to provide a distributed acoustic sensor and sampling data gathered from a plurality of sensing portions of the fibre. The sampled data is then processed to provide a real-time indication of the acoustic signals detected by the sensing portions of the fibre. The real-time indication provides information to an operator or controller of the downwell process with real-time feedback data regarding what is happening during the downwell process which allows the identification of any problems and adjustment of the process parameters.
This invention relates to the fibre optic distributed acoustic sensing to detect P and S waves in a solid medium. Distributed acoustic sensing can be achieved using an unmodified fibre optic by launching optical pulses into the fibre and detecting radiation which is Rayleigh backscattered there from. By analysing the returns in analysis bins, acoustic disturbances can be detected in a plurality of discrete longitudinal sections of the fibre. The present invention extends such fibre distributed acoustic sensing to detection of S and P waves.
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
Methods and apparatus for tracking objects in conduits, especially for tracking the movement of a pig in a pipeline, are disclosed. Distributed acoustic sensing is used to obtain signal returns from a plurality of discrete longitudinal sensing portions of a fibre optic cable which is laid along the length of the conduit. The method involves detecting an acoustic signature corresponding to the object moving in the conduit. The acoustic signature may comprise a series of pressure pulses caused by the object traversing joints etc. in the conduit. Preferably the method involves detecting pressure waves caused by the object as it moves through the conduit. Detecting the characteristic pressure wave signal provides discrimination of the object from other acoustic disturbances. In pipeline applications a pig can be tracked in real time, if the pig stops moving an alert can be generated and the location of the pig will be known.
G01D 5/48 - 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 à base de radiation d'ondes ou de particules
G01S 5/00 - Localisation par coordination de plusieurs déterminations de direction ou de ligne de position; Localisation par coordination de plusieurs déterminations de distance
A method for monitoring a fluid carrying conduit by introducing an acoustic pulse into the conduit, and interrogating an optic fibre positioned along the path of said conduit to provide distributed acoustic sensing. By measuring the response at each of a plurality of locations, a conduit condition profile can be derived. A condition profile can be obtained quickly and easily with minimum disruption to the pipeline infrastructure and contained flow. Existing optic fibres running along the path of a pipe can be employed for sensing purposes, allowing relatively long spans of pipeline to be monitored with only limited access to the pipe.
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
brevets
