Published: December 2002 | IBC’s 17th Annual Conference on Floating Production Systems | December 2 – 3, 2002 | London, ENGLAND
Abstract
Authors:
Allsop, A., Hardisty, P., Tuohy, J., Sheldrake, Dr. T.
Deepwater Flexible Risers & Flowlines – A Decade of Case Studies in Brazil
Published: November 2002 | DOT International Conference and Exhibition XIV – “Flexible Solutions for Today and Tomorrow” – | November 13 – 15, 2002 | New Orleans, Louisiana, USA
Abstract
Offshore oil and gas exploration in deep water continues to provide the industry with new production opportunities and significant technical challenges. Less than three decades ago saw the first installation of flexible pipe in offshore oil and gas developments. Flexible pipe solutions have become synonymous with the use of floating production systems spanning the water column in remote locations, connecting subsea structures with the surface to facilitate the retrieval of hydrocarbons and the injection of water and gas.
Remarkable advances have been made in the development of unbonded flexible pipe structures to meet these challenges, driven to a large extent by Petrobras’s pioneering deep water developments offshore Brazil. These developments have been made possible through research programs funded by Petrobras. Discovered in 1985, the Marlim field, located in the northeastern part of the Campos Basin, was the first field to benefit from these programs. The development of this field was underpinned by the 1986 PROCAP research program focusing on record breaking technologies required to develop not only the Marlim field, but also future deepwater fields, in water depths down to 1,000m.
By 1990 Wellstream had designed and manufactured its first dynamic flexible riser for operation in 1,000m water depths which laid the foundations for Wellstream’s continuing long term deepwater relationship with Petrobras. In 1999 Wellstream set new standards in the development of flexible pipe by becoming the first company to qualify flexible pipe products to 2,000m water depth for the Roncador field, thus meeting the challenge set down by Petrobras in the PROCAP 2000 research program.
Over the decade of the 1990s, significant design and manufacturing challenges were overcome through inhouse research and development programs coupled with support from TCAs(a) with Petrobras. This paper provides an important appraisal of the development and advancement of flexible risers and flowlines for deepwater applications. The information is captured in a number of case studies spanning different field development projects in water depths of 650m to 2,000m over the last ten years. The paper concludes with a summary of the challenges faced in future developments over 2,000m water depth.
Authors:
Tuohy, J., DePaula, M. T., Plank, R. J., Santos, S., Martin, S.
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.
Flexible Pipe Technology – Spanning the Water Column in Deepwater Field Developments
Published: November 2002 | OSEA (Offshore South East Asia) Conference | October 29 – November 1, 2002 | Singapore
Abstract
The recovery of hydrocarbons in water depths up to 2000 metres to date and in the future beyond these water depths, presents significant technical challenges to the designers of recovery systems. Met-ocean characteristics, relatively low reservoir temperatures and pressures also serve to compound these challenges. Flexible pipe has become synonymous with the use of floating production systems spanning the water column, connecting subsea structures to facilitate the retrieval of hydrocarbons and the injection of water and gas. Innovation to unbonded flexible pipe’s technically complex multi-layer structure of helically wound metallic wires and tapes and extruded thermoplastics has ensured that the
product remains one of the key enabling technologies, particularly for deepwater developments. Recent developments include the application of flexible pipe technology in hybrid risers systems, large diameter export loading lines, and topside high-pressure applications.
This paper discusses Halliburton Wellstream’s approach to the use of innovative design techniques to ensure that the company is positioned at the forefront of new flexible pipe technologies. Case studies will be used to illustrate some of the existing technological breakthroughs provided by Wellstream and already in operation at various water depths world-wide. An insight into a typical comprehensive test programme associated with the qualification of a new product is also provided.
Authors:
Tuohy, J., Martin, S.
Application of Finite Element Modelling in the Qualification of Large diameter Unbonded Flexible Risers
Published: June 2002 | 21st International Conference on Offshore Mechanics and Arctic Engineering | June 23, 2002 | Oslo, Norway
Abstract
Unbonded flexible pipe has a proven track record in the offshore oil and gas industry for more than 20 years. The product is synonymous with the use of floating production systems spanning the water column and connecting subsea structures to facilitate the retrieval of hydrocarbons, provision of water injection systems and the export of processed or semi-processed fluids to main trunk pipelines or onshore. Unbonded Flexible pipe is a technically complex multi-layer structure of helically wound metallic wires and tapes and extruded thermoplastics.
In 1996 Wellstream was awarded a major contract for the supply of flexible risers and flowlines as part of the Norsk Hydro Troll Olje Gas Province Development located in 350m water depth 80km west of Bergen. The development consists of two main fields, Troll East (31/3 and 31/6) and Troll West (31/2) which together have an estimated production life in excess of 50 years, making it one of the worlds largest offshore developments. Norsk Hydro is responsible for the development and operation of the production facilities.
The scope of supply included 15-inch internal diameter, 213 barg design pressure, dynamic risers for the export of oil and gas from the platform to shore. At contract award, Wellstream was finalising the location of their European Manufacturing site, a facility which would have the capability of manufacturing unbonded flexible pipe with external diameters up to 24-inches.
The design, manufacture and qualification of a large diameter oil and gas export riser for service in the Norwegian sector of the North Sea, considered to be one of the most severe environments in the offshore industry, provided unique challenges and attributes. These risers have now been in service for over two year, following an extensive qualification programme. This paper provides an insight into the integrated approach adopted during qualification with the successful application of finite element technology to aid full-scale testing. During a full-scale test program a finite element simulation of a 15 metre long prototype pipe was performed with special emphasis on the evaluation of contact forces between the flexible pipe and a bend limiting structure. The finite element analysis program package ANSYS is chosen for this simulation due to its special feature of contact/target elements. The paper illustrates that the use of Finite Element Modelling is indeed capable of predicting the observed behaviour of prototype risers, which are subjected to a series of dynamic load cases, in a Dynamic Test Rig (DTR). Finally, the paper concludes that focus should now be given to the advantages of using finite element tools that are verified by full scale testing to reduce development costs and schedules.
Authors:
Zhang, Dr. W., Tuohy, J.
A Three-Dimensional Finite Element Analysis of Unburied Flexible Flowline – A Case Study
Published: June 2002 | 21st International Conference on Offshore Mechanics and Arctic Engineering | June 23, 2002 | Oslo, Norway
Abstract
Pipelines in the service of conveying hot fluid will tend to expand due to pressure and differential temperature. However, since the flowline is generally fixed at the end terminations to rigid structures or equipment, such an expansion will be restricted in longitudinal direction. This is particularly the case for the section remote from the pipe ends, and results in an axial compression in the pipe section. In many cases, a subsea flowline has to be trenched or buried for the purposes of protection and thermal insulation. Consequently, the lateral movement of a flexible flowline is greatly limited, and an upward displacement is encouraged that may become excessive. Eventually, the flowline may lift out of the trench when the uplift resistance provided by the backfill cover and self-weight of the flowline is gradually overcome by the strain energy built up in the flowline. For flexible pipe, it is this excessive upward deformation being termed as the Upheaval Buckling, which can be prevented by employing adequate downward restraint, such as sand bag / rock dump or by designing a subsea pipe route to overcome this phenomenon. In this paper a case study of the full three-dimensional finite element analysis of a trenched but unburied 6.0-inch production flowline is presented following a description of Wellstream Finite Element Method (FEM) based methodology for Upheaval Buckling analysis of flexible pipes. The effect Bending Stiffness Hysteresis and Upheaval Creep – unique to flexible pipe characteristics, is considered in addition to the general loads such as the flowline self-weight and backfill, pretension, pressure, temperature distribution and prescribed forces (either concentrated or distributed) and displacements. The effects of environmental loads, such as the action of currents that would result in scouring off the backfill, can also be addressed.
The finite element analysis program package ANSYS was chosen for this case study due to its special feature of ANSYS Parametric Design Language (APDL) and contact/target elements; and the general three-dimensional shell and solid elements were used to represent the flexible pipe and trench soil respectively.
Authors:
Zhang, Dr. W., Tuohy, J.
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.
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.
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.
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 | @pen 
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