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.

Justin Tuohy Publications

Qualification of a 15-Inch ID Flexible Riser for Export Oil & Gas Service

Published: November 2002 | Marinflex ’99 – 3rd European Conference on Flexible Pipes, Umbilicals and Marine Cables – Materials Utilisation for Cyclic and Thermal Loading | May 26 – 27, 1999 | London, ENGLAND

Introduction

Unbonded flexible pipe has been used in the offshore oil and gas for more than 20 years. The product is synonymous with the use of floating production systems in spanning the water column connecting subsea structures to retrieve hydrocarbons, water injection systems and the exporting of processed or semi processed fluids to main trunk pipelines or onshore. The basic pipe design for a dynamic application, Fig. 1, consists of a stainless steel internal carcass for collapse resistance, an extruded thermoplastic polymer layer for retaining the internal fluid integrity, a carbon steel interlocking hoop strength layer to provide internal pressure capacity, (a secondary non-interlocked hoop strength layer, for high pressure applications), helically wound carbon steel tensile armour wires to provide axial strength capacity, and an extruded external thermoplastic polymer layer which is watertight, to prevent the ingress of seawater to the annulus. Anti-wear extruded polymer or tape layers are applied between adjacent steel armour layers.

A 15-inch, 213 barg export flexible riser system for both oil and gas, designed for service in 360 m water depth at the Troll C Platform in the Norsk Hydro Troll Olje Field Development is being qualified for service. This paper provides an insight to the qualification process for unbonded flexible riser for the offshore service [1, 2], and updates on the present status of the programme.

 

Authors:

Tuohy, J., Kalman, M., Chen, B., Williamson, D., Wilhelmsen, A., Berge, S., Sævik, S., Løtveit, S. A.

Justin Tuohy Publications

Unbonded flexible pipe solutions for the ultra deep water challenge

Published: March 1999 | Institute of Marine Engineers; “Deep and ultra deep water Offshore Technology” | March, 1999 | Newcastle Upon Tyne, ENGLAND

Abstract

This paper discusses the development of unbonded flexible pipe technology to meet the challenges of ultra deep water floating production systems. Flexible pipe is a multi-layer structure of helically wound metallic wires and tapes and extruded thermoplastics. By considering the integrated design of the layers of the flexible pipe, greater structural utilisation is achieved. The collapse resistance of the carcass is enhanced by the support of the hoop strength layer. The tensile armour layer in conventional pipe consists of high strength steel rectangular wires wound in opposing directions to provide torque balance.

These are replaced by light weight carbon fibre/polymer thermoplastic composite strip. Significant weight reductions are achieved for pipes designed to meet the same performance requirements. Some of the results of tests conducted to qualify the composite armour pipe structure are presented herein. Finally an example based on the functional design techniques is presented to illustrate the advantage of using hybrid unbonded flexible risers for the deep and ultra deep water developments.

Authors:

Tuohy, J.

Justin Tuohy Publications

The use of Unbonded Flexible Pipe Technology in the Onshore and Offshore Oil & Gas Industry

Published: September 1998 | Western European Graduate Education in Marine Technology (WEGEMT) 27th School, Modern Marine Design | September 9, 1998 | University of Newcastle Upon Tyne, England

Abstract

This paper discusses the development and makeup of unbonded flexible pipe technology for the Offshore and Onshore Oil & Gas Industry. Focus is given to the design, manufacture, and testing of unbonded flexible pipe to meet the challenges of shallow and deep water floating production systems. Flexible pipe is a multi-layer structure of helically wound metallic wires and tapes and extruded thermoplastics. Layer by layer, the typical materials employed in the flexible pipe are described along with their functional requirements within the overall pipe structure. From micro finite element analysis to predict the behaviour of the layers of the pipe to global finite element analysis which takes into consideration the environmental and vessel loading on the pipe structure are considered herein. Functional and design requirements are described, along with material selection and manufacturing requirements. The documentation generated with the product design and manufacture is presented. Finally the factory acceptance tests performed prior to load out are described, as well as packaging and a brief overview of installation.

 

Authors:

Tuohy, J.