Justin Tuohy Publications

Pipe and Coupling Design Methodology for Reinforced Thermoplastic Pipe (RTP) Products

Published: October 2000 | 3rd International Conference on Composite Materials for Offshore Operations | October 31 – November 2, 2000 | Houston, Texas, USA

Abstract

Wellstream is a global solutions provider of flexible pipe systems for the conveyance of oil and gas production fluids. As part of the Company’s global diversification program Wellstream have enhanced their solutions portfolio by recently introducing a totally non-metallic composite pipe.  This product is called Reinforced Thermoplastic Pipe (RTP). The development of RTP’s has benefited significantly from Wellstreams expertise in unbonded flexible pipe technology for both onshore and offshore applications utilising the inherent benefits to provide a lower cost product derivative.

Applications are initially targeted at the onshore hydrocarbon market. This product is also suitable for shallow water developments, and other diversified markets which include gas transmission, water transportation, chemical process pipework and mining applications. RTPs can be used in place of and replace the more traditional carbon steel pipeline systems. Due to ease of installation, higher resistance to corrosive environments and extended service life, the RTP has the potential to reduce project capital expenditure and minimise operating costs.

This paper details the design methodology for polyethylene/aramid fibre based reinforced thermoplastic pipe and end-fitting couplings. For onshore applications the service life design criteria are specifically concerned with chemical resistance to internal fluids, resistance to internal pressure, tensile and bending loads, resistance to ultra violet degradation and gas permeation.

Authors:

Chapman, Dr. B., Tuohy, J., Bulmer, G., Bolam, G., Kalman, K., Sheldrake, Dr. T., Soens, C.

Justin Tuohy Publications

Flexible Pipe continues to Pioneer Ultra Deep Water Flowline Riser System Solutions

Published: October 2000 | 3rd International Conference on Composite Materials for Offshore Operations | October 31 – November 2, 2000 | Houston, Texas, USA

Abstract

Offshore Oil & Gas Exploration and Production in deep water continues to provide the industry with significant technical challenges.  Remarkable advances have been made in the development of unbonded flexible pipe structures to meet these challenges. Less than three decades ago saw the first installation of flexible pipe in offshore oil & gas production.  By 1990, flexible pipe was qualified and being installed in dynamic service up to 1000 m water depth.  This paper discusses the innovative design techniques adapted, combined with the use of advanced materials, to expand the water depth/diameter envelope for flexible pipe. An insight into the research and development program which led to the first qualification, installation and operation of unbonded flexible pipe for up to 2000 m water depth is presented.  With the advantages of rapid deployment using low cost installation methods, high reliability and structural redundancy, and increased flexibility in vessel and mooring system design, flexible pipe continues to be a preferred solution for deepwater flowlines and risers.   The methodologies developed to address the deepwater challenges that are addressed in this paper include:

  • The requirement for increased hydrostatic collapse resistance, and the ability to predict the lower bound collapse pressure so that lower safety factors can be employed, thus reducing weight and cost.
  • Increased axial compression resistance to withstand the reverse end cap load due to high external pressure.
  • Reduced weight to reduce top tension and floating structure buoyancy requirements. Both composite material substitution for steel structural reinforcement, and riser section design optimization techniques are considered.

Options for flow assurance solutions using flexible pipe are also presented, including both active heating systems and high thermal resistance products.  The technical challenges to employing flexible pipe in water depths up to 3000 m will also be addressed.

Authors:

Kalman, K., Chen, B., Loper, C., Tuohy, J.

Justin Tuohy Publications

Unbonded Flexible Pipe Solutions – An Established Technology for Offshore Nova Scotia & Newfoundland Field Environments

Published: November 2000 | 19th Offshore Technology Association of Nova Scotia – Petroleum Society Technical Seminar: “New Opportunities – New Challenges” | October 3 – 5, 2000 | Halifax, Nova Scotia, Canada

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 75 MPa, with sour service fluids, for typical internal pipe diameters up to 380 mm (15-inch) for production applications, and even larger in export applications, in water depths as deep as 2000m. 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 Wellstream’s flexible pipe technology been qualified for ultra deep water applications to 2000m, applicable for the future developments of the Scotian Shelf and the Flemish Pass.

Authors:

Tuohy, J., Wang, Dr. D., Baldwin, L.

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.

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.