A new underwater digital radiography based inspection system for rapid integrity assessment of offshore oil and gas flexible risers, RiserSure, has recently been put through its paces for the first time in seawater field trials.
RiserSure is based on a collaborative project which secured funding from the European Horizon’s 2020 research and innovation programme. The project consortium partners – Innovative Technology and Science Ltd, IKNOWHOW SA, MISTRAS Group, London South Bank University and TWI Ltd – are developing the innovative system to be able to image any kind of damage that is present in the various metal layers within a flexible riser, with the additional aim of rapidly bringing to marketing a commercially ready product.
Flexible risers – used to carry oil and gas from subsea oil wells to floating production storage and offloading (FPSO) vessels – are complex structures, operating under severe conditions, that are expected to operate for the life of an oil field which may be up to 30 years. The catastrophic failure of a subsea flexible riser could have disastrous environmental and economic consequences, therefore, the ability to assess them effectively is of major concern to the oil and gas industry.
Many FPSO operators believe that subsea radiography is the only inspection method able to provide the type of information required to detect defects of concern in flexible risers. Previous underwater radiography has typically been achieved with film and imaging plates, however, the disadvantage is that after each exposure, the film or imaging plate must be returned to the surface for developing and processing. RiserSure seeks to address this by deploying an underwater digital x-ray detector and gamma source, certified to 100m depth rating and already developed to Technology Readiness Level (TRL) 6, mounted on a computer controlled scanner.
A team of consortium representatives travelled to The Underwater Centre in Fort William, Scotland to put RiserSure through a series of tests on a section of flexible riser in seawater conditions. With TWI responsible for organising the field trials, the system was integrated with an Irridium-192 radioactive gamma source and lowered, with the riser, into the seawater-fed Loch Linnhe. The team had full management of RiserSure from the control room on the surface through an umbilical link, allowing the system to image a full 360 degree section of the riser. High quality, radiographic images of the riser were captured which revealed the riser’s internal structure. Prior to the seawater trials, RiserSure had been subjected to laboratory based trials which demonstrated that the system had the capability to transition to seawater operation.
The seawater trials were successful in proving that the RiserSure concept works effectively, and this has informed the next step in the system’s development whereby it will undergo an improvement cycle to ensure that it is ruggedised for offshore use. The overall objective of the project is to bring the RiserSure system to market.
Ian Nicholson, TWI’s Project Manager for RiserSure explained ‘This new digital radiography based underwater inspection system will offer a number of benefits to industry including:
- access to a cost-effective solution enabling intensive, continuous inspection regimes for high risk areas
- no downtime or loss of operating revenue because the riser does not have to be removed from service
- a reduced risk of accidents and environmental damage, and improved safety of personnel
- the ability to carry out flexible riser inspections eight times faster than when using ultrasound, meaning completion can be achieved in days rather than weeks
- the ability to accommodate riser diameters from 200mm to 300mm in circumference; and
- provision of a fouling tolerant system.
More information can be found at http://www.risersure.eu/. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730753.