Producing the Intelligent Riser: Advances in Fiber-Optic Monitoring and Visualization Applications Within Flexible Risers

Abstract

Unbonded flexible risers are a critical part of offshore field architecture bringing oil and gas from seabed to platforms on the surface. A failure in operation will result in stop of production and hence a significant loss of revenue. Risers are subject to a number of loading issues including internal and external pressure, vessel motions and current and wave actions. As a result, risers, endure significant strain levels which can impact on their integrity and functionality. The recent implementation of fiber optic monitoring embedded in flexible risers, is an important step towards turning risers into inspectable structures. The embedded monitoring systems ensure the asset can operate safely at its optimum level for the maximum period of time. The combined use of optical point sensors and fully distributed sensors allow various events to be monitored. This includes breach of outer sheath, condensate build up, polymer temperature, pipe temperature during shut in, fatigue and wire break. The traditional industry method for combating these issues has been extensive onshore testing on small sections of the riser allowing the operator to build up a bank of fatigue and reliability data which is used to statistically forecast the strains and stresses the riser will encounter. This data takes into account expected changes throughout the lifecycle of the riser, such as material degradation and environmental issues including storms and hurricanes. The main inspection method in operation to back this up has been expensive inspection campaigns by diver or ROV focusing on external damage. New advances in optical technology and riser manufacturing techniques mean that a suite of real-time monitoring can provide a far more accurate picture of a riser's condition during operation. This improves decision making by allowing structural and temperature issues to be detected at the earliest possible stage and rectified in the most efficient manner, ensuring risers satisfy safety and regulatory requirements and help maximize oilfield productivity. The enabled condition dependent maintenance of risers will reduce the need for expensive ROV operations for inspection. Real time riser monitoring is set to play an increasingly important role as the operators start to insist on the adoption of this technology in the risers delivered to them. As oil production reaches into deeper and deeper water depths, the real time understanding of the integrity of the risers will become paramount. This paper details the advances that have been made in optical monitoring and visualization techniques and their application within the intelligent riser.

Guidelines on Composite Flexible Risers: Monitoring Techniques and Design Approaches

“…Due to their application, marine risers are usually insulated to resist seabed temperatures. Different researchers have presented different studies on monitoring of marine risers, such as fatigue monitoring using shape-sensing devices [53,[66][67][68][69], fibre-optic monitoring [54,[70][71][72][73], intelligent systems [74][75][76], optical sensing [51,[77][78][79][80][81], Riser Integrity Management (RIM) [82,83], flexible pipe integrity assurance [36,69,84], pipeline condition monitoring [85][86][87], vibration monitoring for armour failure [63,67,68,86], pipeline surveillance monitoring [88], and leak detection systems [76,86,[89][90][91].…”

“…Different monitoring sensors and monitoring techniques are used on composite structures and optical fibre materials [47][48][49][50]. One such technique is the Rayleigh backscatter via its Optical Backscatter Reflectometer (OBR) and the use of a distributed fibre optic network to identify accidental impact damage early [51][52][53][54][55][56]. This method delivers high spatial resolution strain and temperature measurements from several sensors placed all along the optical cable.…”