Ultra-deepwater mooring

Cambridge University has begun a three-year project to improve modelling methods for ultra-deepwater mooring and riser developments in the oil and gas industry.

In collaboration with BP Research and funded by engineering firm Noble Denton, the project will address the difficulties exploration and production developments face in water deeper than 1,500m.

RV Ahilan, Noble Denton’s assurance and consulting managing director, said: ‘Developers feel that their projects lose some viability, particularly when they go into ultra-deepwater, because of the uncertainties that come with it. Essentially this project is trying to develop a methodology that avoids the need for scale modelling but that gives developers the same level of confidence.’

Existing modelling methods for ultra-deepwater construction usually include the use of computational modelling — a time-consuming process because of the large volume of data it captures. Physical scale-model testing faces difficulties because of restrictions made to the size of testing tanks. Ahilan hopes the research will overcome these constraints by improving the understanding of the dynamics and exploring new approaches to physical modelling.

‘We are trying to find some analytically equivalent mooring and riser designs that mimic the ultra-deep system as accurately as possible,’ he added. ‘If you can turn a 3,000m depth problem into a 1,000m water-depth problem, then you can do a model test of a 1,000m-depth water problem — but understanding the physics for that transformation will be our biggest challenge.’

The research team also hopes to develop physical modelling solutions, including the use of actuators to mimic the bottom of the sea bed and dynamic similitude to provide a passive shallow water-line with the same vibrational characteristics as a full water line.

Ahilan hopes to begin modelling at a testing facility in the next two to three years.

Ellie Zolfagharifard