Justin Tuohy Publications

Combining Innovative Design Techniques with Advanced Materials – Flexible Pipe Continues to Pioneer Ultra Deep Water Riser System Solutions

Published: June 2000 | IBC 5th Annual Conference “Advances in Riser Technologies” | June 5, 2000 | Aberdeen, Scotland

Abstract

This paper discusses how unbonded flexible pipe technology has overcome the challenges of floating production systems in deep water and continues to be the pioneer for ultra deep water riser system solutions. Since flexible pipe is a multi-layer structure of helically wound metallic wires and tapes and extruded thermoplastics, greater structural utilisation is achieved by considering the integrated design of the layers in its make-up. Reference is made to functional design techniques to illustrate the advantages of using hybrid unbonded flexible risers to span the water column. Continued with an overview of the solutions provided to overcome some of the other ultra deep water challenges such as axial compression during installation, to the development of flow assurance techniques to overcome temperature issues during operation and shutdown, are addressed herein. Finally, an insight into the research and development program which led to Wellstream being the leaders in qualification of conventional flexible pipe technology in water depths of 2000m is given.

Authors:

Tuohy, J., Fraser, D.

Justin Tuohy Publications

Flexible Pipe Solutions – An Established Technology for Offshore Newfoundland Field Environments

Published: June 2000 | NOIA 16th Annual International Petroleum Conference “East Coast Canada Oil & Gas: 2000 and Beyond” | June 20 – 22, 2000

Abstract

Unbonded flexible pipe solutions are a critical element of floating production systems for the production of oil and gas in offshore field developments. Current applications of flexible pipe solutions encompass high temperatures of up to 130ºC, design pressures as high as 500 barg, with sour service fluids for typical internal pipe diameters up to 15-inch for production applications, and even larger in export applications. Severe environmental conditions; extreme wave and current loads coupled with significant vessel excursions, challenge the design and construction of flexible pipe structures.

In designing a new pipe structure for a riser system application, which is outside the existing envelope of qualification, a full program of prototype testing is usually undertaken to verify the fitness for purpose of the pipe for the intended application. This programme incorporates full scale dynamic tests on prototype pipes, with combined loads of tension, bending and internal pressure. This simulates the vessel loading on the riser during the life of field. The loading conditions for the tests presented are based on floating production systems in the North Sea environment. Examples are given of floating production systems currently in operation in the North Sea to which these rigorous testing regimes were applied.

End fittings are a critical component of the flexible pipe system. They must assure a leak tight transition between subsea and surface facilities, during the applied severe environmental loads and thermal cycling due to start-up and shutdowns, with changes in the fluid barrier material properties over the designed service life. The results of analyses and tests conducted to verify the integrity of the end fitting with thermal cycling and fluid barrier changes due to high temperature production fluids are presented herein.

This paper concludes with a summary of the innovation and qualification programmes that has resulted in flexible pipe technology being qualified for ultra deepwater applications to 2000 m, applicable for the future developments beyond the Grand Banks.