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.