Abstract: Embodiments of the present invention provide a cable for optical fiber sensing applications formed from fiber wound around a cable core. A protective layer is then preferably placed over the top of the wound fiber, to protect the fiber, and to help keep it in place on the cable core. The cable core is preferably of a diameter to allow bend-insensitive fiber to be wound thereon with low bending losses. The effect of winding the fiber onto the cable core means that the longitudinal sensing resolution of the resulting cable is higher than simple straight fiber, when the cable is used with an optical fiber sensing system such as a DAS or DTS system. The achieved resolution for the resulting cable is a function of the fiber winding diameter and pitch, with a larger diameter and reduced winding pitch giving a higher longitudinal sensing resolution.

Abstract: Externally generated noise can be coupled into a fluid carrying structure such as a pipe, well, or borehole so as to artificially acoustically “illuminate” the pipe, well, or borehole, and allow fluid flow in the structure or structural integrity to be determined. In the disclosed system, externally generated noise is coupled into the structure being monitored at the same time as data logging required to undertake the monitoring is performed. This has three effects. First, the externally generated sound is coupled into the structure so as to “illuminate” acoustically the structure to allow data to be collected from which fluid flow may be determined, and secondly the amount of data that need be collected is reduced, as there is no need to log data when the structure is not being illuminated. Thirdly, there are signal processing advantages in having the data logging being undertaken only when the acoustic illumination occurs.

Abstract: A method and a system are provided, in which acoustic signals received by distributed acoustic sensors are processed in order to determine the position of a source or sources of the acoustic signals. The method and system are able to determine the position of several acoustic sources simultaneously, by measuring the corresponding several acoustic signals. Furthermore, the strength of the acoustic signal or signals can be determined. The location of the acoustic source may be overlaid on a map of an area being monitored, or be used to generate an alarm if perceived to correspond to a threat or an intrusion, for example in a pipeline monitoring application. Alternatively, the method and systems can be used to monitor a hydraulic fracturing process.

Abstract: Embodiments of the present invention address aliasing problems by providing a plurality of discrete acoustic sensors along a cable whereby acoustic signals may be measured in situations where the fibre optic cable has not been secured to a structure or area by a series of clamps. Acoustic sampling points are achieved by selectively enhancing the acoustic coupling between the outer layer and the at least one optical fibre arrangement, such that acoustic energy may be transmitted selectively from the outer layer to the at least one optical fibre arrangement. The resulting regions of acoustic coupling along the cable allow the optical fibre to detect acoustic signals. Regions between the outer layer and the at least one optical fibre arrangement that contain material which is acoustically insulating further this enhancement since acoustic waves are unable to travel through such mediums, or at least travel through such mediums at a reduced rate.

Abstract: A probe is provided that contacts the inner surface of the casing or other production tubing and imparts energy to the surface at the contact point, for example as heat energy or mechanical energy. Energy is imparted around the circumference of the casing, and a fiber optic distributed sensor located on the outer surface of the casing is used to measure and record the energy that it receives whilst the probe is moved to impart energy around the circumference. A record of energy versus position of the probe around the circumference can be obtained, from which maxima in the detected energy measurements can then be found. The position around the circumference which gave the maximum measurement should be the position at which the optical fiber of the fiber optic distributed sensor is located. In addition, an ultrasonic arrangement is also described, that relies on ultrasonic sound to provide detection.

Abstract: Externally generated noise can be coupled into a fluid carrying structure such as a pipe, well, or borehole so as to artificially acoustically “illuminate” the pipe, well, or borehole, and allow fluid flow in the structure or structural integrity to be determined. In the disclosed system, externally generated noise is coupled into the structure being monitored at the same time as data logging required to undertake the monitoring is performed. This has three effects. First, the externally generated sound is coupled into the structure so as to “illuminate” acoustically the structure to allow data to be collected from which fluid flow may be determined, and secondly the amount of data that need be collected is reduced, as there is no need to log data when the structure is not being illuminated. Thirdly, there are signal processing advantages in having the data logging being undertaken only when the acoustic illumination occurs.

Abstract: An optical fiber distributed acoustic sensor system includes weak broadband reflectors inserted periodically along the fiber. The reflectors reflect only a small proportion of the light from the DAS incident thereon back along the fiber, typically in the region of 0.001% to 0.1%, but preferably around 0.01% reflectivity per reflector. In addition, to allow for temperate compensation to ensure that the same reflectivity is obtained if the temperature changes, the reflection bandwidth is relatively broadband. In some embodiments the reflectors are formed from a series of fiber Bragg gratings, each with a different center reflecting frequency, the reflecting frequencies and bandwidths of the gratings being selected to provide the broadband reflection. A chirped grating may also be used to provide the same effect. In preferred embodiments, the reflectors are spaced at half the gauge length i.e. the desired spatial resolution of the optical fiber DAS.

Abstract: Apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre can be used for point sensors as well as distributed sensors or the combination of both. In particular, this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. Advantages of this technique include a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.

Abstract: The invention relates to installations for fibre optic monitoring of articles, and apparatus and methods for forming such installations, including a modular system and components for forming a fibre optic monitoring installation. Applications of the invention include the monitoring of vessels, chambers, and fluid conduits in industrial processing plants, and the invention has particular application to monitoring large vessels, for example temperature monitoring of vessels used in catalytic reforming processes. Convenient installation on or removal from the article being monitored is achieved by providing a support structure for the fibre optic length, which presents the fibre optic length in a preconfigured orientation suitable for monitoring the article. In a particular embodiment of the invention, the fibre optic length is disposed on a panel in a plurality of dense spiral patterns.

Abstract: An optical fiber sensing system includes a sensing optical fiber and one or more optical amplifiers in series with the sensing fiber and arranged to increase the power of sensing pulses travelling along the fiber to thereby increase the range of the sensing system. The optical fiber sensing system is one selected from the group including an optical fiber distributed acoustic sensor (DAS), an optical fiber distributed temperature sensor (DTS), or an optical time domain reflectometry (OTDR) system.

Abstract: Exemplary embodiments include an apparatus for imaging a volume of material contained inside a vessel. The apparatus includes a plurality of synchronized acoustic sensors positioned at a periphery of an inner volume of the vessel. A processor combines the outputs of the acoustic sensors to identify at least one ambient noise source of the industrial process generating a noise field that illuminates an internal volume of the vessel and to provide an image of the material by temporal and spatial coherent processing of the transmission and reflection of the noise field generated by the noise source.

Abstract: Embodiments of the present invention address aliasing problems by providing a plurality of discrete acoustic sensors along a cable whereby acoustic signals may be measured in situations where the fiber optic cable has not been secured to a structure or area by a series of clamps, as described in the prior art. Acoustic sampling points are achieved by selectively enhancing the acoustic coupling between the outer layer and the at least one optical fiber arrangement, such that acoustic energy may be transmitted selectively from the outer layer to the at least one optical fiber arrangement. The resulting regions of acoustic coupling along the cable allow the optical fiber to detect acoustic signals. Regions between the outer layer and the at least one optical fiber arrangement that contain material which is acoustically insulating further this enhancement since acoustic waves are unable to travel through such mediums, or at least travel through such mediums at a reduced rate.

Abstract: A probe is provided that contacts the inner surface of the casing or other production tubing and imparts energy to the surface at the contact point, for example as heat energy or mechanical energy. Energy is imparted around the circumference of the casing, and a fiber optic distributed sensor located on the outer surface of the casing is used to measure and record the energy that it receives whilst the probe is moved to impart energy around the circumference. A record of energy versus position of the probe around the circumference can be obtained, from which maxima in the detected energy measurements can then be found. The position around the circumference which gave the maximum measurement should be the position at which the optical fiber of the fiber optic distributed sensor is located. In addition, an ultrasonic arrangement is also described, that relies on ultrasonic sound to provide detection.

Abstract: Apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre can be used for point sensors as well as distributed sensors or the combination of both. In particular, this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. Advantages of this technique include a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.

Abstract: A prefabricated mat-like structure having lengths of fiber mounted thereon or therein in a predetermined deployment pattern that provides a high spatial density of fiber to give increased spatial sensing resolution is described. The prefabricated mat-like structures may be very easily deployed by being placed against and/or wrapped around an object to be monitored, typically being fastened in place by clamps or the like. In addition, easy removal from the object is also obtained, by simply unfastening the mat-like structure, which may then be redeployed elsewhere.

Abstract: The invention relates to installations for fiber optic monitoring of articles, and apparatus and methods for forming such installations, including a modular system and components for forming a fiber optic monitoring installation. Applications of the invention include the monitoring of vessels, chambers, and fluid conduits in industrial processing plants, and the invention has particular application to monitoring large vessels, for example temperature monitoring of vessels used in catalytic reforming processes. Convenient installation on or removal from the article being monitored is achieved by providing a support structure for the fiber optic length, which presents the fiber optic length in a preconfigured orientation suitable for monitoring the article. In a particular embodiment of the invention, the fiber optic length is disposed on a panel in a plurality of dense spiral patterns.

Abstract: The present invention provides novel apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre. The present invention can be used for point sensors as well as distributed sensors or the combination of both. In particular this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. The present invention offers unique advantages in a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.

Abstract: An interferometer apparatus for an optical fibre system and method of use is described. The interferometer comprises an optical coupler and optical fibres which define first and second optical paths. Light propagating in the first and second optical paths is reflected back to the optical coupler to generate an interference signal. First, second and third interference signal components are directed towards respective first, second and third photodetectors. The third photodetector is connected to the coupler via a non-reciprocal optical device and is configured to measure the intensity of the third interference signal component directed back towards the input fibre. Methods of use in applications to monitoring acoustic perturbations and a calibration method are described.

Abstract: A downhole device is provided that is intended to be co-located with an optical fiber cable to be found, for example by being fixed together in the same clamp. The device has an accelerometer or other suitable orientation determining means that is able to determine its positional orientation, with respect to gravity. A vibrator or other sounder is provided, that outputs the positional orientation information as a suitable encoded and modulated acoustic signal. A fiber optic distributed acoustic sensor deployed in the vicinity of the downhole device detects the acoustic signal and transmits it back to the surface, where it is demodulated and decoded to obtain the positional orientation information. Given that the device is co-located with the optical fiber the position of the fiber can then be inferred. As explained above, detecting the fiber position is important during perforation operations, so that the fiber is not inadvertently damaged.

Abstract: The present invention provides novel apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre. The present invention can be used for point sensors as well as distributed sensors or the combination of both. in particular this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. The present invention offers unique advantages in a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.