Justin Tuohy Publications

The Application of Unbonded Flexible Risers & Flowlines in Hostile Environments – Shallow Water Case Studies

Published: November 2002 | International Conference on the Application and Evaluation of High-Grade Linepipes in Hostile Environments | November 8 – 9, 2002 | Yokohama, JAPAN

Abstract

Unbonded flexible pipe has a proven track record in the offshore oil and gas industry for more than 25 years. The product is synonymous with the use of floating production systems spanning the water column, connecting subsea structures to facilitate the retrieval of hydrocarbons, provision of water and gas injection systems and the export of processed or semi processed fluids to main trunk pipelines, to onshore, or to floating storage units. Unbonded Flexible pipe is a technically complex multi-layer structure of helically wound metallic wires and tapes and extruded thermoplastics. Applications of flexible pipe solutions in service encompass high temperatures of up to 130ºC, design pressures as high as 100 MPa, with sour service fluids for typical internal pipe diameters up to 16-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. 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. A summary of 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 is included in the case studies presented.
This paper demonstrates the ability of unbonded flexible pipe solutions in the form of dynamic risers and flowlines to be the key enabler for the production of hydrocarbons to floating production systems in hostile environments.

 

Authors:

Tuohy, J., Sheldrake, Dr. T.

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.