Selasa, 03 Februari 2015

DNV invites industry to participate in pipeline integrity management JIP

 Det Norske Veritas is preparing a new recommended practice for offshore pipeline integrity management and is inviting upstream producers and pipeline operators to participate in this joint industry project.
There are over 20,000 mi of pipeline infrastructure in the Gulf of Mexico servicing and transporting about 30% of US domestically produced oil and gas. The challenge is that some lines remain in operation after 40 years of service, and many beyond their originally anticipated service life. Recent hurricane events in the Gulf of Mexico demonstrated the vulnerability of this supply network and the consequences of disruptions.
While some potential leaks or failures might be attributable to events such as subsea mudslides or hurricanes, most are a result of the condition of the pipeline itself. It is imperative to manage and maintain the integrity of the subsea pipelines, DNV says.
DNV, in cooperation with the industry, is preparing a new Recommended Practice (RP) for offshore pipeline integrity management. The RP will address in-service issues from the early design phase through to the operational phase. The objective is for the RP to be a state-of-the-art document, developed in close cooperation with the industry and reflecting industry practices and sound engineering practices for establishing and maintaining the integrity of subsea pipeline systems, DNV says.
The RP will identify the components of a subsea pipeline integrity management program and will provide a highly detailed framework that producers or pipeline operators can use when preparing the integrity management programs for their own pipeline systems. It will also include a detailed framework for a direct assessment methodology, which would be applicable to the subsea pipelines and would be submitted to the National Association of Corrosion Engineers, International (NACE) for review and approval.
This project is a follow-up to a 2006 project for the US Department of the Interior (DOI) Minerals Management Service (MMS), in which DNV assessed the integrity practices used by operators in the GoM.
DNV encourages upstream producers and pipeline operators to participate in the development of this JIP, which is intended to be practical and cost effective, while maintaining a commitment to system integrity, safety, and the protection of the environment, the company says.
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Pipeline Ending Manifold (PLEM) /PLET

Subsea manifold is a flow-routing subsea hardware (subsea flow router) that connects between subsea trees and flowlines. It is used to optimize the subsea layout arrangement and reduce the quantity of risers connected to the platform. If connected to dual flowlines, the manifold can typically accommodate pigging and have the capability of routing production from a particular tree to a particular flowline.
Pipeline End Manifold (PLEM)

It a simpler version of a cluster manifold generally designed to direct fluids for only one or two subsea Christmas trees. A PLEM generally connects directly to a subsea flow line without the use of a pipeline end termination (PLET).
Manifold Compenents

Four well manifold P&ID.
A manifold is typically composed of the following major components:
  • Pipework and valves – contains and controls the production and injection fluids.
  • Structure framework – protects and supports the pipework and valves.
  • Subsea connection equipment – allows subsea tie-in of multiple pieces of equipment. Types include vertical, horizontal and stab-and-hinge-over connections.
  • Foundation – interface between the manifold structure and seabed.
  • Controls Equipment – allows the remote control of any hydraulically actuated subsea manifold valves and the monitoring of production and injection fluids. Control pods may be either internal or external to the manifold.
Valves
Valves on the manifold are essential for directing and controlling the flows. They can be either manual or hydraulically actuated. Sometimes chemical injection valves are placed on the manifold as well.
  • Branch valves are generally slab type gate valves (similar to tree valves). Their sizes are based on the production/injection tree size.
  • Flowline header valves are also gate type, but ball valves have been used previously. Their sizes are based on the flowline size.
  • Materials are chosen for compatibility with production and injection fluids. Most of time, it is CRA-clad.
  • Double barrier philosophy generally used against production fluids.
    • Two valves in series
    • One valve and one pressure cap
    • Primary seal is generally a metal-to-metal seal
Pipework
A wide range of pipework configurations is possible. Each header connects to an individual flowline. the pipework sizing is based on the tree piping size and the flowline diameters. The main circuit is designed to accommodate pigging operations. The material of construction needs to be compatible with production and injection fluids.
  • Test headers can be incorporated to test individual or groups of trees
    • Test headers can be a second or even third header isolated in the manifold
  • Insulation may be required for unscheduled or emergency shutdowns
Control System
Control system for the manifolds is the same as the control system for the trees. Multiple options for the control system have been used in the manifold design
  • No controls on the manifold. The manifold is controlled by tree subsea control modules (SCMs).
  • SCMs on the manifold.
  • Manifold with control system distribution units with flying leads going to trees.
Framework Structure
The framework is a welded structure to provide support for the pipework and valves and contain the foundation interface structure. The pipework is allowed to float inside the framework within limits and it is not rigidly attached to the frame. The frame can also be used for lifting and landing of the jumper tie-in tools.
Foundation
  • Mud mats – a simple foundation resting directly on the seabed, generally with a short skirt around the perimeter to resist lateral loads.
  • Piles – long cylindrical structures embedded into the soil intended to hold a subsea structure above the seabed. Foundations may utilize one or more individual piles.
  • Intermediate Structures – an intermediate structure can be used to interface a subsea manifold with a pile foundation to reduce weight of the manifold structure or to ease retrieval of the manifold. Intermediate structures can be either retrievable or permanent structures.
Tie-ins to wells and flowlines
The tie-in hubs placed on the outer edge of the manifold, which are used to tie-in jumpers that bring in fluid from the production wells and export fluid into the flowlines (production manifold). The tie-in sizing is based on the tree piping size and the flowline diameters. and the loads applied from the flowlines
Insulations
Generally gas manifolds are not insulated and oil manifolds are insulated. For oil production, insulation is necessary to allow adequate cool-down time to treat or remove trapped production water. Gas production is generally treated continuously with chemicals to prevent hydrates.
Deployment method
The following vessels are typically used for manifold deployment:
  • Drill Rig: through moon pool or keel-hauled on drill string
  • Heavy Lift vessels (Derrick Barges): through moon pool or over side
  • Work-class vessels: over side on crane or winch
The following equipments are typically required:
  • Manifold hydraulic installation tool
  • Sling sets, either wire rope or synthetic fiber
Applicable API Specs
  • API Spec 17P – Templates and Manifolds
  • API Spec 17D – Specifications for subsea wellhead and Christmas tree equipments
  • API Spec 17A – Recommended practice for design and operation of subsea production systems
  • API Spec 17H, ISO 13628-8 – ROV Interfaces
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Pig Launchers & Receivers

Pig launchers and pig receivers are installed on pipelines to launch and receive pipeline pigs, pipeline spheres and pipeline inspection tools. Pig launchers & pig receivers offer a safe and effective means of inserting and removing pipeline pigs to and from pipelines. Pipeline Engineering fabricates pig launchers and pig receivers to meet the specific requirements of a pipeline.
Our in-house design, engineering, fabrication and testing capability is used to produce all types of pig and sphere launching and receiving systems.
The pig launchers and pig receivers we fabricate range from simple barrel pig launchers and receivers through to complete skid mounted units with associated equipment including actuated valves, quick opening closures, instrumentation, pig signallers and control systems.
The pig launchers and receivers we fabricate are suitable for onshore, offshore and subsea pipelines. All units are designed and fabricated to relevant required pipeline and vessel design codes including:
Pig Launchers & Receivers
  • ASME U Stamp Division 1 & 2
  • ASME VIII
  • NACE
  • BS 5500
  • ASME B31.3, B31.4, B31.8
We fabricate pig launchers and pig receivers from 2" to 60" designed with operating pressures up to 400 bar. Pig launchers and pig receivers are produced in a range of materials, from low strength carbon steel, to high strength carbon steel, and where specified, stainless steel, duplex stainless steel and carbon steel internally clad with corrosion resistant inconel materials.
Pig Launchers & Receivers
Multiple pig launchers are designed to allow the sequential launching of pigs and spheres. Using our automatic multiple pig launching system a series of pigs can be launched into a pipeline without having to repeatedly depressurise and re-pressurise after each pig launch. The process can also be controlled from a remote location. This is particularly relevant on unmanned platforms such as offshore platforms and sour service applications.
Sphere release fingers on sphere launchers are used to control the release of a series of spheres into a pipeline.
Pig Launchers & ReceiversPipeline Engineering will design pig launcher and receiver systems which are 'tailor-made' to meet specific operational requirements. This can include:
  • Multiple valve operation
  • Automatic or manually operated pig and sphere release systems
  • Integrated skid mounted packages
In addition to the supply of newly manufactured pig launchers and pig receivers, Pipeline Engineering provides an inspection, maintenance and refurbishment service to existing in service pig launchers and receivers.
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Vortex Induced Vibration of Offshore Pipeline

In fluid dynamics, vortex-induced vibrations (VIV) are motions induced on bodies interacting with an external fluid flow, produced by – or the motion producing – periodical irregularities on this flow.
A classical example is the VIV of an underwater cylinder. You can see how this happens by putting a cylinder into the water (a swimming-pool or even a bucket) and moving it through the water in the direction perpendicular to its axis. Since real fluids always present some viscosity, the flow around the cylinder will be slowed down while in contact with its surface, forming the so called boundary layer. At some point, however, this boundary layer can separate from the body because of its excessive curvature. Vortices are then formed changing the pressure distribution along the surface. 

When the vortices are not formed symmetrically around the body (with respect to its midplane), different lift forces develop on each side of the body, thus leading to motion transverse to the flow. This motion changes the nature of the vortex formation in such a way as to lead to a limited motion amplitude (differently, then, from what would be expected in a typical case of resonance).

VIV manifests itself on many different branches of engineering, from cables to heat exchanger tube arrays. It is also a major consideration in the design of ocean structures. Thus study of VIV is a part of a number of disciplines, incorporating fluid mechanics, structural mechanics, vibrations, computational fluid dynamics (CFD), acoustics, statistics, and smart materials.

images

Pipelines at the bottom of the sea are susceptible to ocean currents. Even relatively calm currents can induce turbulences in the wake of the pipeline, which results in the pipeline to start 'dancing'. Pipe vibrations can trigger fatigue, with catastrophic fracture as a result. Consequently, when designing submarine pipelines, caution is being paid to avoid such vibrations. Our research engineers use powerful software to predict submarine pipeline stability.


“Dancing at Great Depth”

Even relatively calm currents can induce turbulences in the wake of the pipeline, resulting in pipeline oscillations. The pipeline vibrations can trigger fatigue, causing accelerated damage. Since fatigue damage can give rise to complete fracture with catastrophic consequences, extreme caution is being paid in order to avoid such vibrations when designing submarine pipelines. Flow patterns around submarine pipelines greatly depend on the velocity of the sea currents and on the tube diameter. 

When the current becomes too strong, turbulences show up in the wake of the pipeline. This vortex shedding exerts an alternating force on the pipeline. Consequently, the pipeline is being subjected to cyclic loading. The pipeline starts to dance, following a characteristic ‘number-eight’ path. Under cyclic loading, the pipe is being exposed to fatigue, which could cause the pipe to fail under surprisingly modest stresses.
Vortex induced vibrations

Current State of Art

Much progress has been made during the past decade, both numerically and experimentally, toward the understanding of the kinematics (dynamics) of VIV, albeit in the low-Reynolds number regime. The fundamental reason for this is that VIV is not a small perturbation superimposed on a mean steady motion. It is an inherently nonlinear, self-governed or self-regulated, multi-degree-of-freedom phenomenon. It presents unsteady flow characteristics manifested by the existence of two unsteady shear layers and large-scale structures.

There is much that is known and understood and much that remains in the empirical/descriptive realm of knowledge: what is the dominant response frequency, the range of normalized velocity, the variation of the phase angle (by which the force leads the displacement), and the response amplitude in the synchronization range as a function of the controlling and influencing parameters? Industrial applications highlight our inability to predict the dynamic response of fluid–structure interactions. 

They continue to require the input of the in-phase and out-of-phase components of the lift coefficients (or the transverse force), in-line drag coefficients, correlation lengths, damping coefficients, relative roughness, shear, waves, and currents, among other governing and influencing parameters, and thus also require the input of relatively large safety factors. Fundamental studies as well as large-scale experiments (when these results are disseminated in the open literature) will provide the necessary understanding for the quantification of the relationships between the response of a structure and the governing and influencing parameters.

It cannot be emphasized strongly enough that the current state of the laboratory art concerns the interaction of a rigid body (mostly and most importantly for a circular cylinder) whose degrees of freedom have been reduced from six to often one (i.e., transverse motion) with a three-dimensional separated flow, dominated by large-scale vortical structures.

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Energy sector to drive demand for spiral welded pipes and tubes, according to new report by global industry analysts, inc.

GIA announces the release of a comprehensive global report on the Spiral Welded Pipes and Tubes markets. Global market for Spiral Welded Pipes and Tubes is projected to reach 24.6 million tons by 2018, driven by economic recovery, level of activity in the energy sector, and intensifying pipeline construction activity.

Spiral welded pipes market, though encountering overcapacity conditions particularly in North America, is expected to witness steady growth in the upcoming years driven by the implementation of new pipeline projects. Investments in oil and gas exploration and production, which are influenced by prevailing crude oil & gas prices, have a considerable impact on the demand for spiral welded pipes and tubes. Resurgent world economy and consequent increase in the demand for industrial natural gas is expected to drive up momentum of the spiral welded pipes market.
Global demand for spiral welded pipes, which are primarily used in the transportation of oil and gas and in water transportation projects, is closely linked to the investments in the energy sector. The energy sector makes use of spiral welded pipes with diameters of up to 60” and up to 80 feet in length. Another factor that is expected to fuel demand for spiral pipes and tubes is new pipeline construction activity due to the shift of population from traditional centers that would necessitate development of infrastructure for delivering oil and natural gas to the new locations. Demand for spiral welded pipes is also expected from the replacement market, as most of the existing pipeline infrastructure, particularly in developed regions, has reached their end of useful life. Structural applications of spiral welded pipes are also gaining momentum, specifically with additional activity occurring in port, offshore loading and infrastructure improvement sectors.
As stated by the new market research report on Spiral Welded Pipes and Tubes, Asia-Pacific represents the largest market worldwide, driven primarily by increased use in transporting natural gas. Besides Asia-Pacific, Latin America ranks among the fastest growing regional markets with compounded annual growth rate ranging between 7.5% and 9.0% over the review period. North American market, on the other hand, is encountering testing times owing to weak demand and overcapacity conditions. Oversupply is the major concern for spiral welded pipes market particularly with regard to large diameter double submerged arc welded or DSAW line pipes, which finds use in transmitting oil, natural gas liquids, and natural gas to consumers from drilling locations.
Despite the prevailing conditions, potential opportunities are expected primarily from the implementation of new pipeline projects in the upcoming years, resurgent growth of the US economy, and increased demand from natural gas exploration operations. Also, overcapacity conditions are expected to fade away in the coming years, as several megaprojects are set to be taken up across the world, particularly in regions such as Southeast Asia, Australia, Middle East, Africa, and West Asia.
Replacement of aging infrastructure offers huge potential for pipe manufacturers. The need to replace old pipelines is particular high in the US and Russia, where pipeline networks were mostly installed during the 60s and 70s. With the average lifespan of oil and gas transportation pipes ranging between 25 and 30 years, opportunities in the replacement market are huge, particularly for HSAW pipes. In the US, replacement demand holds enormous potential as a result of the recent enactment of the legislation that necessitates more inspections to be carried out, which could increase the likelihood of pipeline replacements. The Act is likely to play a critical role in enabling manufacturers of large diameter line pipes to survive the tough economic and overcapacity conditions.
Major players profiled in the report include American SpiralWeld Pipe Company LLC, ArcelorMittal SA, Borusan Mannesmann Boru Sanayi ve Ticaret A.S., Europipe GmbH, EVRAZ North America, JFE Steel Corporation, Jindal SAW Ltd., Man Industries Ltd., National Pipe Company Ltd., Nippon Steel & Sumitomo Metal Corporation, PSL Limited, Shengli Oil & Gas Pipe Holdings Limited, Stupp Corporation, Volzhsky Pipe Plant, UMW Group, and Welspun Corp Ltd.
The research report titled “Spiral Welded Pipes and Tubes: A Global Strategic Business Report” announced by Global Industry Analysts Inc., provides a comprehensive review of market trends, issues, drivers, company profiles, mergers, acquisitions and other strategic industry activities. The report provides market estimates and projections for all major geographic markets including the US, Canada, Japan, Europe (France, Germany, Italy, UK, Spain, Russia and Rest of Europe), Asia-Pacific (China and Rest of Asia-Pacific), Middle East, and Latin America.
For more details about this comprehensive market research report, please visit –
http://www.strategyr.com/Spiral_Welded_Pipes_and_Tubes_Market_Report.asp
About Global Industry Analysts, Inc.
Global Industry Analysts, Inc., (GIA) is a leading publisher of off-the-shelf market research. Founded in 1987, the company currently employs over 800 people worldwide. Annually, GIA publishes more than 1300 full-scale research reports and analyzes 40,000+ market and technology trends while monitoring more than 126,000 Companies worldwide. Serving over 9500 clients in 27 countries, GIA is recognized today, as one of the world’s largest and reputed market research firms.
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STOPAQ - Offshore Corrosion Prevention and Insulation Systems

When Frans Nooren founded STOPAQ in 1988, he started a waterproofing contracting company aimed at solving many civil structure water problems, a major concern in a country like the Netherlands. Drawing on his practical experience, he set out to improve sealing technology products and developed an innovative product, which he demonstrated to great success by sealing leaks in the harbour walls at Rotterdam.
Due to erosion of the soil behind the dock wall pilings, corrosion had taken place and corroded the sheet from the rear, leading to perforations. These had to be sealed from the harbour side using novel technology involving a sealing compound applied and cured under water. This product was the start of a new generation of sealants and coatings.

Polyisobutene resin sealants for the offshore industry

The polyisobutene resin technology STOPAQ's product range is based on make it ideal for field joint coating of pipelines. The company's latest innovation of visco-elastic coatings – which are patented innovative polymer technology and available worldwide – can provide pipeline owners and operators with reliable, long-lasting anti-corrosion coatings for field joints and for the repair of damaged areas on the main pipeline coatings.
As the coatings are 100% self-healing, chemical and temperature-resistant, and less likely to damage in service, they can be easily and quickly applied without the need of special equipment or highly skilled operators. This, in turn, means there are fewer application and through life costs.

Advanced corrosion prevention and insulation systems

The offshore world requires advanced corrosion prevention and insulation systems. Corrosion processes can sever offshore equipment and pipe rupture may occur. Hard and tough coatings may break. Very low PH (2-3) electrolyte solutions can cause CUI. Other chemical reactions and or moisture / water penetration must be prevented at great depths.
In response to the offshore industry's demands, STOPAQ and BASF have joined forces. The result of combining STOPAQ's visco-elastic corrosion prevention layer with BASF's PU is a cost-effective solution delivering long-term protection against corrosion by locking out negative influences. We see stopping corrosion as our common mission now. Via our system, we can offer you more control in all process steps from preparation, application and control beyond design life.

Corrosion prevention systems for offshore pipelines and platforms

Pipelines and platforms need to be safe constructions – for people and for the environment. STOPAQ / BASF Offshore can seal spools, under insulation, under fireproofing, J-tube filling, flanges, risers, christmas trees, pp-coating repair, pipe joints, subsea repair, and piles (splash zone). STOPAQ / BASF applications can be found on many important offshore installations worldwide and on offshore pipeline joints.
STOPAQ / BASF offers fully integrated solutions, including service preparation on-board of lay barge vessels. The joint system offers a simple, safe and fast-turnaround job, guaranteeing 100% adhesion. Mechanical protection is ensured by using tapes, shrinkable sleeves or PU infill.

Tailor-made corrosion-resistant coating systems

STOPAQ / BASF's coating system can be tailor-made for each project, and easily applied. Furthermore, it also allows a quicker preparation of steel and adjacent factory applied coating by at least St2/3 brushing method, cold application of the visco-elastic anti-corrosion layer, and immediate and permanent attachment of the impermeable visco-elastic layer to steel, concrete, polypropylene, polyurethanes and polyethylene. There is no risk of osmosis.
Some of the system advantages are:
  • Increasing the speed of application
  • Eliminating the need of flame torch
  • No need for primers
  • Cost-effective: reduces inventory requirements eliminating diameter specific solutions
  • Outstanding impact resistance
  • Cold flow; providing corrosion protection by penetrating into the finest pores of the substrate
  • Very surface tolerant; no grit blasting, only wire brushing or hand tool cleaning required
  • Higher temperatures resistance
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Pipeline Material Grade Selection

General PrincipleThe steels applied in the offshore oil and gas industry vary from carbon steels (taken from American Petroleum Institute standards- Grade B to Grade X 70 and higher) to exotic steels (i.e. duplex). The following factors are to be considered in the selection of material grades:
  • Cost;
  • Resistance to corrosion effects;
  • Weight requirement;
  • Weldability
The higher the grade of steel (up to exotic steels) the more expensive per volume (weight). However, as the cost of producing high grade steels has reduced, the general trend in the industry is to use these steel of higher grades.
Fabrication, Installation, and Operating Cost Considerations
The choice of material grade used for the pipelines will have cost implications on:
  • Fabrication of pipeline;
  • Installation;
  • Operation.
Fabrication
The cost of steels increases for the higher grades. However, the increase in grade may permit a reduction of pipeline wall thickness. This results in the overall reduction of fabrication cost when using a high grade steel compared with a lower grade steel.
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F
abrication
Installation
It is difficult to weld high grade steels, and consequently lay rate is lower compared to laying the lower grade steels. However, should the pipeline be laid in very deep water and a vessel is laying at its maximum lay tension, then the use of high grade steel may be more suitable, as the reduction in pipe weight would result in lower lay tension. In general, from an installation aspect, the lower grade steel pipelines cost less to install.
39
Pipeline Installation
Operation
Depending on the product being transported in the pipeline, the pipeline may be subjected to:
– Corrosion (internal)
– Internal erosion;
– H2S induced corrosion.
Designing for no corrosion defect may be performed by either material selection or modifying operation procedures (i.e. through use of chemical corrosion inhibitors).
Material Grade OptimizationOptimization of material grade is rigorously applied today based on experience gained from the past 20 years of pipeline design, and the technical advances in linepipe manufacturing and welding. The optimization is based on minimization of fabrication and installation cost while meeting operating requirements. As the selection of material grade will have a significant impact on the operating life of the pipeline, the operator is normally involved in the final selection of material grade.
Source:Bai, Yong and Bai, Qiang. Subsea Pipelines And Risers. USA: Elsevier Inc. 2005.

O-lay, offshore pipeline and riser installation technology

For O-lay offshore pipeline and riser installation, welding and inspection is done onshore

The offshore pipeline and riser construction and installation technology described here is very different from the common offshore technologies used at present. By using the O-lay technology operational production costs can be reduced compared to the existing general methods of pipe laying offshore. With O-lay, the pipe laying operations will be faster than other methods used today. Pipe line installation of larger diameter pipe can be as fast as 25 km per day. Furthermore the technology is safer because there are less people working in the offshore environment and the offshore operations are done in a shorter period of time.
The bottleneck of welding and testing on the traditional lay-barge is not a procedure that is part of the installation process anymore. Welding and testing are done on an onshore construction site.
The main difference between the new, state of the art, patented O-lay system and the existing systems is that the total length of the pipe is welded, post weld treated and tested onshore on a site that is near the waterfront.  Depending on the local situation, series of "long pipes", with a length of 50 to 1500 meter, are produced and temporarily stored in the pipe yard till they are transported into the water.
spoolbase
Deformation in elastic area
The "long pipes" are welded together in the final pipe line string and then transported into the water. If needed the pipeline will be kept afloat with the help of floatation devices. From the floating pipe a large spiral will be formed with a diameter that is sufficiently large to prevent the pipe from deforming in its plastic area. To remain within the 0,2% strain of the steel, the diameter of the floating circle is 500 times the pipe diameter
(Example: A pipe with OD 20 inch (500mm) will form a spiral of 250 meter diameter).

Quality of welds and improved fatigue resistance

The O-lay technology has the great advantage that welding can be performed under optimal conditions. With traditional S-lay the pipeline is lowered in the water just after the welds are finished. This cools down the welds and the HAZ relatively fast and induces local area's with high tensile stresses. Due to cyclic stresses these local area high tensile stresses can initiate cracks in the material.  With O-lay there is ample time to cool the welds slowly and to apply post weld treatments like ultrasonic impact treatment (UIT), needle peening and weld toe dressing to improve the weld geometry. These applications increase the resistance against crack initiation when a cyclic load is applied.

Floating transport

The spiraled pipe can form a total length of more than 100 km pipeline. When the pipe spiral has reached its predetermined length, the whole spiral can be transported (with the help of tugboats as is shown in the photo below) to the place where the installation has to be done. When the spiral has arrived at the location where the pipe will be installed, the spiral shall be unwound and with the help of a special prepared vessel  be lowered to the seabed. This method of pipe line installation is especially interesting for water depths where the S-lay method is being used and also in very shallow waters.
8inch spiral being towed toward sea smal-laag
In the picture a tug boat pulls the floating spiral.

Retrieving

Instead of installing pipe with the combination of S-lay and a spiralled pipe it is also possible to retrieve pipe from the sea bottom. Thereafter the pipe can then be transformed into a large spiral after inspection. In this way it is possible re-use the pipe again on a different location. This will reduce the costs even further and could be very interesting to use on very small oil or gas fields.

Tested

Several tests in laboratory and under real conditions (as seen in photo above) have shown that the method described is feasible for pipelines of all diameters.

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Intelligent flexible pipe can improve tieback design

The oil and gas industry has used flexible pipelines since the 1970s. Several thousand kilometers have been manufactured, installed, and put in operation. Many things can be done to make flexible pipe "intelligent." This is demonstrated in a technical feasibility study for expanding the producing Tui oil field.
Though intelligent pipelines can take many forms, two significant and proven applications are integrated service umbilical (ISU) and integrated production bundle (IPB). The ISU combines the function of both an umbilical and flexible pipeline. The IPB is essentially the same as an ISU, with an added active heating component. Both are made of a core and an assembly.
The core of either is a standard flexible structure. Flexible structures are made of several different layers. Each layer performs a different function. The inner most layer, known as an interlocking carcass, acts to withstand any hydrostatic collapse. Next is a leak-proof plastic sheath, known as the pressure sheath. This keeps the bore fluid contained. The pressure vault acts to withstand the internal pressure of the bore fluid. Then there are two sets of armor wires cross-wound for torsional stability. These wires take any tensile loading of the flexible pipe. The final layer of a standard flexible pipe is a plastic sheath to prevent water ingress into the annulus between the two plastic sheaths.
The assembly can comprise a bundle of hoses, cables, steel tubes, optical fibers, and insulation wrapped around the core. Assembly components typically are used for gas lift, chemical injection, hydraulic lines, power communication cables, heat tracing wires, and more. The assembly is held together by high-strength tape and a plastic outer sheath.

Feasibility study

Intelligent pipeline benefits have been demonstrated in a technical feasibility study on a Tui oil field expansion. As part of this study, tieback solutions of a production flowline, umbilical, gas lift flowline, and gas export flowline are considered.
Tui is 50 km (31 mi) offshore New Zealand in the Taranaki basin. In operation since 2007, Tui was New Zealand's first standalone subsea development. As part of its subsea field layout, it comprises four wells linked to an FPSO.

Design data

The main criteria for design of the flexible structures in this case are a production flexible flowline, a gas lift flexible flowline, and gas export flexible flowline are as follows (courtesy AWE):
table 1
The umbilical components are part of a previous umbilical design supplied for the project, so each component has been qualified for its function. The feasibility study called for the following:
table 2

Solution

The base case would be to supply three separate flexible pipeline structures and one umbilical. The alternative is to combine the gas lift, production, and umbilical into one pipeline known as the IPB, resulting in the manufacture, supply, and operation of only two pipelines.
In this case, the production line forms the core: the gas lift and umbilical form the assembly. The advantages of an IPB in this situation are reduced installation time, reduced field complexity, and optimized thermal performance.
Reduced installation time and reduced complexity arise because there is one structure instead of three. Reduced installation time is especially beneficial in this case because the Taranaki basin is known for harsh weather. The reduced complexity of the field means fewer pipes on the seabed and a cleaner subsea layout. This is advantageous for fields with existing infrastructure. Optimized thermal performance comes because the gas lift tubes are integrated into the structure. So, where the production line would have the highest temperature, the gas lift would have the lowest. Optimized thermal performance might keep the production line above a critical value to mitigate hydrate formation.
The Tui oil development is offshore New Zealand.
The Tui oil development is offshore New Zealand.
The IPB design is made up of a standard rough bore (with interlocking carcass) structure which forms the core and an assembly. The assembly consists of six thermoplastic hoses, two cables, and four steel tubes. The thermoplastic hoses can be used either for chemical injection or hydraulic controls. The cables are used for power and communication to subsea equipment, and the 3-in. gas lift line is split into four 1-in. steel tubes. All these components are evenly distributed around the flexible pipe for torsional stability, and are separated by fillers. Fillers keep these components in place as well as transfer any mechanical loading to the core. Both fillers and components are wound in an S-Z manner around the core of the flexible pipe resulting in torsional stability of each of these components.
In detailed design, the following options might bring advantages in cost savings and/or enhanced performance. These include the following:
  • Similar outer diameter components
  • Adding passive insulation
  • Active heating
  • Temperature monitoring.
The use of similar outer diameter components allows the use of one filler type. This reduces the manufacturing complexity of the flexible pipe structure. Passive insulation takes the form of strips of synthetic foam which can be added as part of the assembly.

Active heating

There are three ways to provide active heating to a flexible pipeline: hot water circulation, the use of heat tracing cables within the armor layer, and/or a dedicated active heating section above the core of the flexible pipe. Active heating is useful where hydrate formation is an issue and the bore fluid has to be kept above a critical temperature. It is especially useful for shutdown and restart operations.
Hot water circulation is beneficial because the hot water is warmest where it is injected, which is where the production line is coldest. This can mean an increase in diameter, which is not optimal. This makes the use of heat tracing cables advantageous.
Heat tracing cables replace every few tensile armor wires. The number and location of these cables depend on the heating requirements, and those are governed by factors such as water depth, length of pipeline section, bore fluid temperature, and critical temperature of the bore fluid. If the design of the flexible is governed by tension, a dedicated heating layer above the core of the flexible pipe can be created. The design of the heat tracing cables is unique in the sense that it is a three-phase star connection circuit, which means that the sum of the current phases is nil. Therefore, no return cable is necessary, ensuring a more compact solution.

Temperature monitoring

Technip's temperature monitoring is the distributed temperature sensors (DTS) system. This provides continuous temperature measurement along the length of flowline using optical fibers.
Small bore stainless steel tubes are incorporated in the tensile armor layer during manufacture. Every fourth tensile armor wire is replaced by a steel tube, sometimes with plastic fillers on either side to ensure structural integrity of the steel tubes. At one end fitting termination, the steel tubes join to provide a continuous loop. Post manufacture, the optical fiber is inserted into these steel tubes using a blow down technique.
This involves the use of fluid drag to run the fiber through the control line. A pump pressurizes the system, the tubes provide the drag, and the fittings allow fluid to flow through the system, directing the fiber in the line. The loop in the termination allows the optical fiber to be inserted at one end and retrieved at the other end. This means there is access to both ends of the optical fiber. Double-ended measurements can then be made with no fiber splicing, thereby increasing the accuracy of the measurements.
DTS sends pulses of light down the optical fiber. The ratio of intensities of the two wavelength separated components of the back scattered light yields the temperature at the point of scattering. The time it takes from when the pulse is sent and to when the back scattered light returns gives the location of the temperature. As a result, a temperature versus distance graph for the whole length of the optical fiber can be constructed. The principle is known as Raman OTDR (optical time domain reflectometry).

Graphical user interface

A dedicated system can be created according to project requirements to facilitate the user interface of the system. This can consist of obtaining raw data along the length of the riser system. This can then be split into critical locations along the length of the riser such as touchdown point, gas-lift injection point, and topside. Other functions can be implemented into the system such as alarms in case of detection of cold or hot spots to prevent against hydrate formation and temperature fluctuations in the flexible pipe.
3D representation of an IPB (left). Cross section of an IPB (right).
3D representation of an IPB (left). Cross section of an IPB (right).

Gas export line

The nominal option of the 4-in. gas export line is a standard flexible pipe structure. However, with the use of intelligent options such as active heating, the need for dehydration of gas prior to export onshore could be revisited. This would be useful where there is no offshore processing facility. Active heating could take the form of electrical heat tracing cables integrated into design of the flexible pipe.
3D representation of an IPB (left).
3D representation of an IPB (left). Close up of the DTS system (right).

Qualification and track record

Integrated service umbilicals (ISU) have been used for a number of years. The current record stands at 18. A number of tests have been performed to determine the validity of these intelligent pipeline solutions. These take into account the mechanical behavior of the pipe when subjected to installation loads and hydrostatic loads, the thermal behavior of the pipe due to the integration of active and passive heating, and fatigue behavior of the pipe.
The first test began in 1998-1999. A test sample was fabricated incorporating active heating by hot water circulation. The sample consisted of an 8-in. ID flexible pipe with 11 hoses distributed around the core and passive insulation in the form of 30 mm (≈1.2 in.) of syntactic foam above. This was subjected to several heating and cooling phases. This qualification program resulted in the development of calibrated software in which the global heat exchange coefficient (U-value) of an IPB can be determined accurately as well as software capable of modeling the thermal and hydraulic coupling of an IPB, verifying its performance with regards to flow assurance.
In 2000, a joint industry research and development program (JIP) was formed between Technip and participants to qualify active heating for a flexible pipe. As part of this JIP, two electric heat tracing technologies were tested. The sample incorporated two designs - heat tracing cables as part of the assembly (dedicated heating layer) and heat tracing as part of the armor wires. The sample was then submerged in water and subjected to more than 10 different heating and cooling simulations. Test results were used to validate the design of the IPB as well as software used to design the IPBs.
The JIP also led to the creation of the DTS, which was devised to monitor the temperature along the length of the flexible pipeline during the test. The DTS system was integrated into the test sample as part of the tensile armor wires as well as part of the bundle layer.
Previously manufactured IPBs.
Previously manufactured IPBs.
To complement thermal testing, a full-scale test was done to study the behavior of electrical cables laid in an SZ manner over a core structure. It was found that the dynamic fatigue cycling as well as the heating and cool down phases had no effect on the integrity of the electrical systems. A layer by layer dissection found no significant damage to any of the IPB components.
The JIP paved the way for its first application offshore West Africa. This project is in block 17, 135 km (84 mi) offshore in water depths of between 1,200 m (3,936 ft) and 1,500 m (4,920 ft). For this project, eight 10.75-in. IPBs were supplied. The IPB design consisted of six heat tracing cables, thermal insulation, DTS system, and 24 gas lift tubes evenly distributed around the core of the IPB. A test sample was manufactured prior to final supply which was subjected to a full-scale testing in which the crushing, fatigue and thermal behavior was validated. A full-scale test was performed in a vertical configuration as this is more representative of real-life conditions.

Conclusion

With discoveries in more challenging fields, the implementation of intelligent pipelines is a qualified solution for both new and existing fields. These intelligent pipeline solutions take the form of an integrated service umbilical (ISU) and integrated production bundle (IPB) which can incorporate umbilical functions, active heating components, and the DTS system.
Key advantages of intelligent options can include improved thermal performance, reduced complexity of existing fields/new fields, and minimized installation time. Improved thermal performance can be achieved several ways where the temperature of the bore fluid needs to be kept above a certain critical value. The reduction in complexity of a subsea field layout and minimized installation time arises from incorporating three different flexible structures (gas lift, production, and umbilical) into one pipeline solution.
The ISU design has been in service for many years. IPB is a more recent technology. The IPB is qualified by numerous test programs performed by Technip, which validates the performance of its active heating elements and DTS system. The positive results of these test programs have paved the way for its use on offshore projects; the IPB risers have been successfully implemented on two West Africa field developments and are due to be installed on a project in Brazil.