Testing of Distributed-Temperature Sensing in Flexible Risers and Flowlines
- Chris Carpenter (JPT Technology Editor)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- April 2014
- Document Type
- Journal Paper
- 79 - 83
- 2014. Offshore Technology Conference
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- 80 since 2007
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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 23948, "Full-Scale Testing of Distributed-Temperature Sensing in Flexible Risers and Flowlines," by Nick Weppenaar, Thomas Iversen, and Bo Andersen, NOV Flexibles, prepared for the 2013 Offshore Technology Conference, Houston, 6-9 May. The paper has not been peer reviewed. Copyright 2013 Offshore Technology Conference. Reproduced by permission.
This paper presents results from full-scale testing of a flexible riser equipped with embedded sensors for distributed-temperature sensing (DTS). Testing includes monitoring of accessories mounted on the riser, monitoring of hot spots such as trenched sections of the riser, and detection of breaches of the outer sheath. Applications of such a condition-monitoring system to riser-integrity management (RIM) and production optimization are worth examining.
With the increasing use of flexible-pipe technology—driven by the move of new offshore fields to deeper, more-marginal, and more-challenging conditions— the need for systematic management of the flexible pipes is becoming more apparent. In particular, the full implementation of RIM plays a vital role in ensuring an efficient and safe operation. Riser-condition monitoring and inspection form an important part of integrity management, together with processing and analysis of the monitored data. In that respect, the recently developed technology within optical-fiber monitoring offers unique possibilities for quantifying the integrity of flexible risers during their service life. The advantage of an embedded monitoring system is the ability to survey the riser condition continuously, thus enabling operators to detect potential damages in a timely fashion. The embedded system will allow monitoring in critical areas (e.g., under a bend stiffener or inside an I-tube) where access is limited for externally mounted monitoring systems.
The temperature-monitoring system is a DTS system that uses a standard multimode optical fiber to measure the temperature at all points along the fiber with a given spatial resolution. The principle of implementation into a flexible pipe is shown in Fig. 1. The fiber is mounted on top of the outer tensile layer while being protected from crushing forces. The specific implementation that has been achieved allows for temperature measurements with a spatial resolution in the longitudinal direction of the pipe of approximately 8 cm. Currently, this can be implemented in pipes that are up to approximately 5 km in length, and the sample time can be as fast as 10 seconds per fiber. If a longer pipe length needs to be monitored, this can be achieved at the expense of spatial resolution or temperature resolution.
For the present series of tests, the fiber length is approximately 200 m, which allows for a high temperature resolution. The system measures every 10 seconds, with a temperature resolution of approximately 0.1°C and a spatial resolution of approximately 15 cm.
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