We demonstrate a low-loss, long-range, single-ended distributed optical fiber sensor to measure both temperature and strain simultaneously and unambiguously. By using the Landau¿Placzek ratio and cascaded Mach¿Zehnder interferometric filters, we measure both the intensity and the frequency changes in the Brillouin backscattered signal. Strain and temperature measurements can then be independently resolved. A temperature resolution of 4 degrees C, a strain resolution of 290 muepsilon, and a spatial resolution of 10 m have been achieved for a sensing length of 15 km.

DAS resembles thousands of microphones along the sensing fiber. In railway applications, only a small fraction of all DAS data carries information about the train-rail interaction. Transforming the data to a rail view or train view simplifies analysis and reveals valuable rail and train properties.

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Leakage from pipes is a major issue in both the oil and gas sectors, not only in environmental and economic terms, because of wasting important natural resources, but importantly from a safety perspective. Optical fibre technology offers the possibility of continuous acoustic monitoring of pipelines and remote detection of leaks. In this paper we present results from gas leak measurements made on a specially designed, buried pipeline test rig, for which leak energy radiated directly from the leak (orifice noise) dominates over energy radiated from the pipe wall. Measurements of the orifice noise are made using an optical fibre distributed acoustic sensing system as well as conventional geophones. Both the geophones and the optical fibres are shown to be able to detect the orifice noise, particularly when the fibres were located close to the pipeline. Fibre measurements are found to be limited by both high background noise and by gauge length, which limited the upper frequency limit for accurately determining the phase of the ground response. The measurements indicate that the orifice noise sets up Rayleigh waves in the ground, largely contained in frequencies below 100Hz, the magnitude of which are found to be compatible with predictions from idealised jet theory.The effect of fibre ducting and armouring is also evaluated.

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In this paper we describe a unique and innovative pipeline and flowline monitoring system which has been developed by Schlumberger in collaboration with BP. Applications of the system include pipeline/flowline integrity monitoring and overall optimization of the operation of the pipeline/flowline. Details of the pipeline condition monitoring system (PCMS) components are provided along with the results from comprehensive field trials. The system uses novel optical fibre distributed sensors to provide simultaneous distributed measurements of temperature, strain and vibration for the detection, monitoring, and location of events including: • Third Party Interference (TPI), including multiple simultaneous disturbances; • Geo-hazards and landslides; • Gas and oil leaks; • Permafrost protection. The system performs analysis of the combination of measurands to provide the operator with an event recognition and location capability allowing the most appropriate early response to be initiated. Through the use of newly developed remote, optically powered amplification, an unprecedented detection range of 100km is achieved without the need for any electronics and therefore remote power in the field. A system can thus monitor 200km when configured to monitor 100km in two directions from a single location. As well as detecting the external conditions leading to leaks, this fully integrated system provides a means of detecting and locating small leaks in gas pipelines below the threshold of present online leak detection systems based on monitoring flow parameters. Other benefits include the enhancement of the operator’s existing integrity management program and the potential for reductions in surveillance costs and HSE risks. In addition to onshore pipeline systems this combination of functionality and range is available for practicable monitoring in a wide range of other applications such as: • Long subsea flowlines; • Umbilicals; • Power cables; • Offshore riser systems; • Settlement in tank farms; • Facilities perimeter security. An important deliverable from this work includes the design and field testing of a bespoke optical sensor cable, designed to be sensitive to ground movement to allow distributed strain measurement whilst withstanding the rigors of the pipeline environment. In this paper, we describe the new optical sensing methods developed, and the results of the extensive field trials performed during 2007 and 2008 to fully evaluate and prove the system for use on long hydrocarbon transmission pipelines. Specifically, we demonstrate the detection of small gas releases, simulated earth movement and a number of different types of third party interventions at the full 100km target range.

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