A flexible pipe and a method of manufacturing same according to which the pipe is formed by at least one layer, and an insert disposed in the layer and adapted to limit the strain on the layer when the pipe collapses.
According to the present invention, a solution is provided whereby rather than directly towing a pipe ( 30 ) from a tug ( 11 ), a cable ( 23 ) is suspended between two surface vessels ( 10, 11 ), and it is from this cable ( 23 ) that the pipe ( 30 ) itself is suspended at a plurality of points. By means of this arrangement, stress and fatigue is absorbed by the cable ( 23 ) rather than the pipe ( 30 ), such that the pipe ( 30 ) arrives at its installation point with a correspondingly smaller loss in fatigue life.
Published: December 2002 | IBC’s 17th Annual Conference on Floating Production Systems | December 2 – 3, 2002 | London, ENGLAND
Allsop, A., Hardisty, P., Tuohy, J., Sheldrake, Dr. T.
Published: November 2002 | DOT International Conference and Exhibition XIV – “Flexible Solutions for Today and Tomorrow” – | November 13 – 15, 2002 | New Orleans, Louisiana, USA
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.
Tuohy, J., DePaula, M. T., Plank, R. J., Santos, S., Martin, S.
Published: November 2002 | International Conference on the Application and Evaluation of High-Grade Linepipes in Hostile Environments | November 8 – 9, 2002 | Yokohama, JAPAN
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.
Tuohy, J., Sheldrake, Dr. T.
Published: November 2002 | OSEA (Offshore South East Asia) Conference | October 29 – November 1, 2002 | Singapore
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.
Tuohy, J., Martin, S.
Published: June 2002 | 21st International Conference on Offshore Mechanics and Arctic Engineering | June 23, 2002 | Oslo, Norway
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.
Zhang, Dr. W., Tuohy, J.
Published: June 2002 | 21st International Conference on Offshore Mechanics and Arctic Engineering | June 23, 2002 | Oslo, Norway
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.
Zhang, Dr. W., Tuohy, J.
Published: January 2002 | Fifth International Conference: Pipeline Rehabilitation & Maintenance | January 19 – 23, 2002 | Gulf International Convention Centre, Bahrain
Halliflow[1], a reinforced thermoplastic pipe, has been developed for the transmission of oil and gas production fluids. Field applications are initially targeted at the onshore hydrocarbon market. However, 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. RTP has the potential to reduce operating costs and provide an attractive life of field commercial alternative to carbon steel lines. The RTP development effort has benefited significantly from experience in the technology of unbonded flexible pipe. RTP utilises the inherent benefits of flexible pipe technology to provide a lower cost product derivative.
This paper details the RTP design methodology for polyethylene/aramid fibre based thermoplastic pipes and end fittings. 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.
Dodds, Dr. N., Southern, A., Tuohy, J., Sheldrake, Dr. T.
Published: 2001 | The Journal of Offshore Technology
“Unbonded Flexible Pipe is a viable cost effective solution for the transportation of hydrocarbons from Floating Production, Storage and Offloading (FPSO) vessels to CALM Buoys for tanker transport to shore” – Justin Tuohy, Director, Product Strategy for Wellstream.
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. Since unbonded flexible risers are an obvious solution for floating production and storage systems, being a proven technology spanning three decades, these challenges have already been overcome for the smaller diameter pipe structures. In 1999 Wellstream illustrated the technology lead by being the first manufacturer of flexible pipe to qualify 4-inch and 6-inch internal diameter products to 2000 m water depth for offshore Brazil. Continued developments will have much larger internal diameters qualified to these water depths in the near future………
Justin Tuohy | @pen 
You must be logged in to post a comment.