Justin Tuohy Publications

An Update on Flexible Pipe Technology for Ultra-deepwater Production, Injection and Offloading Systems

Published: September 2001 | IBC Conference, “Technological Advances in Risers, Moorings & Anchorings in Deepwater Fields” | September 18 – 20, 2001 | London, England

Abstract

Offshore exploration for oil and gas is being performed in even more challenging waters, with fields being developed in water depths of 2000 metres and greater. To recover hydrocarbons from these depths a number of technical challenges are presented to the designers of riser and offloading systems. In addition, metocean characteristics and relatively low reservoir temperatures also compound the challenges.

Flexible pipe is a proven solution for conveying fluids from subsea wells to surface vessels in 2000 metres water depth. Solutions are being developed for service in up to 2500 metres. It is now the centre of focus for large diameter offloading systems in deepwater applications particularly in West Africa where significant volumes of crude oil are to be offloaded to other floating structures and tankers.

This paper discusses how Wellstream’s unbonded flexible pipe technology has overcome the challenges of floating production systems in 2000 metres water depth and how its continued development will ensure its incorporation in new pioneering solutions for ultra-deepwater riser systems.

These achievements in technology are applied to the design of large diameter offloading and export systems which are being considered for large field developments. An insight into the design and detailed analysis of the unbonded flexible pipe solutions developed by Wellstream for large diameter export riser systems is provided.

Finally, the paper concludes with an update of the comprehensive full-scale testing program currently ongoing at Wellstream’s global facilities.

Authors:

Tuohy, J., Sheldrake, Dr. T., Williamson, D.

Justin Tuohy Publications

Unbonded Flexible Pipe Technology in Deepwater Developments for Production, and Offloading Systems

Published: March 2001 | 5th Annual Offshore West Africa Conference & Exhibition 2001 “Challenges for the Emerging Frontier” | March 21 – 23, 2001 | Abuja, NIGERIA

Abstract

Offshore exploration for oil and gas is being performed in even more challenging waters, with fields being developed in water depths of 2000 metres and greater. To recover hydrocarbons from these depths a number of technical challenges are presented to the designers of riser and off-loading systems. In addition, met-ocean characteristics and relatively low reservoir temperatures also compound the challenges of offshore West of Africa developments.

This paper discusses how Wellstream’s unbonded flexible pipe technology has overcome the challenges of floating production systems to 2000 metres water depth and how its continued development will ensure its incorporation in new pioneering solutions for ultra deep water riser systems. Specifically detailed reference is made to functional design techniques to illustrate the advantages of using hybrid unbonded flexible risers to span the water column.

The low reservoir temperatures typically found in West of Africa fields dictates that temperature management is crucial in order to minimise heat losses from the reservoir to the processing facilities to reduce the risk of wax deposition, hydrate formation and decreased flowing viscosity. Unbonded flexible pipe technology is also well placed to meet these challenges with a selection of flow assurance tools available.

The paper continues with an overview of the unbonded flexible pipe solutions developed by Wellstream to overcome the other deep water challenges associated with large diameter export riser systems. Finally, the paper concludes with an economic appraisal of why flexible pipe systems should be considered a cost effective solution in the overall CAPEX and OPEX of deep water field developments.

Authors:

Tuohy, J., Avery, A., Martin, S.

Justin Tuohy Publications

Retrieval and Reuse of Unbonded Flexible pipes – A Solution for Reducing Marginal Field Costs

Published: November 2000 | SEN 2000 “ Tieback Technology for the New Millennium” | November 28 – 29, 2000 | London, England

Abstract

Unstable oil prices over the past number of years have resulted in a slowdown of oil & gas field developments. Many of the marginal field developments are no longer viable at typical development budgets and consequently there is a need to continue to develop technology to meet the challenges whilst in parallel substantially reduce associated costs.
Since the mid 1990’s Granherne has been proactive in the drive to reduce costs of Normally Unmanned Installation (NUI) developments around the world in order to release marginal field developments and achieve facility cost reduction of 25-30%. A major element in the future oil and gas business is to find ways of releasing marginal field developments in the 10-25mmbls range characterised by small numbers of wells, Capex budgets of less than $100m and a limited field life of about 2-5 years. Here the potential reuse of facilities and pipelines becomes increasingly financially viable provided they are designed for ease of adaptation and reuse during their lifetime.
Wellstream, has always been proactive in providing cost effective solutions of flexible flowline and riser systems for field developments. Typically a flexible pipe is designed specifically to the operators requirements for a given field with a design life up to 25 or 30 years. However the field may cease production in as little as 5 years but more commonly in 10 to 15 years. In some areas of the world operators have taken advantage of this and consequently flexible pipe is relocated up to 7 times in its life in similar applications. Wellstream has assisted in evaluating the condition of the pipe structures after life of field has been reached.
Much focus has been on reducing subsea and NUI platform costs but the one remaining significant challenge is to find ways of reducing the costs of infield pipelines to host facilities. This area offers at least as much scope as that of the minimum facilities for cost reduction. One way forward is to look at the use of reelable flexible products which offer the greatest potential for reuse. Halliburton companies, Granherne and Wellstream are looking at the development of more cost effective solutions for the marginal field developments. One of the critical issues is the lack of operational data available to assess the remaining life in flexible pipes that have fulfilled the life of field requirement at their current location. Use of condition monitoring allows a service record to be maintained and ease of certification for reuse. Wellstream has been involved in the area of developing online monitoring systems since the early 1990’s and are also proactive participants in Joint Industry Programs in this area. The goal is to achieve a flexible pipeline solution which can be laid and recovered with a modular construction to allow a range of tieback distances to be accommodated. Using this approach it is possible to achieve a serial development of marginal fields around an existing host where both the surface NUI or subsea facilities and associated flowline/umbilical system can be relocated over sequential developments.
This paper discusses the significant potential for cost reduction and savings in this approach to marginal field developments. It addresses the requirement for a change in philosophy and thinking. It also requires collaborative support and co-operation from operators.

Authors:

Tuohy, J., Robinson, Dr. R.

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.