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Collaboration between an oil and gas inspection provider and engineering consultancy has achieved an industry first, combining inspection data with a fully simulation-based irregular wave approach for enabling the life extension of flexible risers.

The partnership between Innospection and INTECSEA; FlexIQ, has established a step change for industry technology by providing life extension assessment for flexible risers based on simulations advised by inspection data. This has been successfully used for Shell Nigeria’s two Bonga flexible risers.

Naren Ramaiah, Head – Pipeline & Integrity, Shell Nigeria said: "Our offloading system is configured with flexible pipelines which are designed for onerous loadings and stresses. Assessing and assuring its integrity regularly is very important for our safe operations. "

This technique combines the two proprietary technologies: the MEC-FIT™ inspection tool and the FLEXAS™ numerical solver which allow high-resolution stochastic fatigue life to be captured based on realistic conditions. 

•    MEC-FIT™ enables inspection of the tensile armour wire layers through the outer sheath of the flexible riser. This technology can be deployed on long riser sections, and is uniquely able to detect defects within multiple layers regardless of the annulus condition. 

•    FLEXAS™ offers the only solution framework available in the industry that computes irregular wave wire stresses using dynamic simulation of high-fidelity finite element models; this eliminates approximations and uncertainties associated with non-simulation based approaches. This solution includes detailed damage modelling from inspection data to produce the industry’s most accurate wire stress computation.

Shell Nigeria commissioned the FlexIQ team to determine the current condition of their flexible risers and provide recommendations for the future safe operation of the Bonga Oil Offloading Risers located offshore Nigeria. Bonga has been producing since 2005 and the risers are currently 15 years into their original 20 year design life. 
 
FlexIQ has been used to re-evaluate the design life and determine the suitability for life extension of the risers. The MEC-FIT™ inspections detected no wire corrosion damage, leading to the FLEXAS™ irregular wave simulations predicting low rates of fatigue accumulation. Embedding the inspection and analysis results into a risk based framework enabled operational risk to be quantified. The analysis predicted safe and reliable operation of the assets well beyond the original design life. 

Andreas Boenisch, Group Managing Director for Innospection, said: "The whole project was very successful and saw us achieve major results for our client to support life time extension.

"Our technology overcomes a challenge many operators face when assessing the integrity of their asset’s flexible risers because they are hung-off subsea and cannot have annulus testing performed, making it challenging to assess the integrity of them. In the case of the Bonga asset, Innospection provided a solution to this which produces valuable data which can be analysed to ensure risers are fit for purpose.”

Dr. Kirsten Oliver, Asset Management Lead for INTECSEA stated; "Interpreting and embedding inspection results into the advanced simulation process has enabled us to truly represent the assets’ condition using state of the art numerical solutions to provide a risk based approach to flexible riser integrity.”