Case Studies
Measurements on damaged fibre
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SENSORNET PROVIDES FIBRE HEALTH CHECK SOLUTION FOR THIRD PARTY SYSTEM
Sensornet’s distributed temperature sensor (DTS) system has proved its ability to carry out world-beating, single-ended measurements on previously installed, but damaged, optical fibres on an offshore platform in Brunei.
Client Requirements
The customer wanted an optical fibre health check on three offshore wells in Brunei enabling Brunei Shell Petroleum (BSP) to quantify the reliability of measurements taken from fibres that were thought to be damaged.
The Monitoring Gap
Alternative monitoring technologies such as thermocouples are not able provide the location of downhole events due to their discrete point measurements. Sensornet’s DTS solutions provide the precise and timely information required by reservoir engineers for complete understanding of production performance.
The Sensornet Solution
The Sentinel DTS system used in the trials is the most technologically advanced distributed temperature sensing system. The self contained system operates with an intuitive user interface allowing fast and simple calibration and configuration. The system has been designed with safety in mind and has been tested to some of the industry’s most rigorous standards. It provides long-range distributed temperature sensing with a resolution of better than 0.01°C.
The work Sensornet carried out for Brunei Shell proved the ability of the Sentinel DTS system to provide not only a health check on the condition of the installed optical fibres, but also a range of accurate spatial and temperature measurements within just six hours.
Sensornet engineers performed all set-up, calibration and healthcheck measurements, and many fine temperature features were resolved in the data which were correlated with known features in the well completion. All fibres had been installed by a third party, using a “pump around” method in which fibre is inserted into a capillary U-tube running down the well, through a “turn-around” at the bottom, and back up to surface.
Substantial Benefits
The health check found immediate problems with the fibre in well ID- 23, which was shown to be damaged significantly along its entire measurable length – so badly damaged, in fact, that meaningful simple single-ended measurements could not be made with this fibre. Sensornet determined that, with its health check technique, it could measure to around 2500m depth before the accumulated losses became too large for meaningful measurements.
The condition of the fibres in the two other wells was shown to be much better, with no measurable degradation on well ID-19 and only small degradation on well BG-7 at all points past the “turn-around” sub. Here, the scale of the damage and its position at the end of the fibre was not expected significantly to affect the accuracy of DTS measurement, so single-ended measurements could be used with confidence.
Measurable Performance
The Sentinel DTS™ provided long-range distributed temperature sensing with a resolution of better than 0.01°C if required. In this (Brunei Shell) application it collected data at a 1°C temperature resolution with a 1m spatial resolution over 5km with an update time of 10 seconds.
The result was clear confirmation of the Sentinel DTS system’s ability to detect and assess damage to installed optical fibres, and to provide accurate, calibrated, fine spatial and temperature resolution measurements.
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