The Acteon customer magazine
V.4 05-08
Re-engineering the conductor installation process Groundbreaking environmental monitoring system ready for shipment Responding to the challenges of hurricane-damaged structures
issue 4 Re-engineering conductor installation Responding to challenges Gap analysis rising to the fore submerged turret buoy mooring
Diary
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05–08 May 15–18 September
For further information please contact Paul Alcock T: +44 1603 227012 F: +44 1603 774175 W: www.acteon.com E: paul.alcock@acteon.com © Acteon Group Ltd 2008
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OTC .08, Houston, Texas, USA Rio Oil & Gas, Rio de Janeiro, Brazil
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Acteon has grown considerably in recent years by expanding existing businesses and bringing new companies into the group, the whole process being driven by our belief of what customers really desire from the service sector.
We often hear about new technology enabling things to be done faster or cheaper, or making the impossible or very difficult possible. All of these are eminently achievable, as shown in some of the features in this issue of S2S.
We see a particularly strong appetite for more cost-effective methods of delivering subsea services. In this regard, there has been a positive response to our initiative to install subsea equipment from the back of anchor-handling or similar vessels, as opposed to more conventional installation methods. Recently, InterMoor took this approach to reduce the cost of installing conductors in the Espirito Santo basin for Shell Brasil Ltda (page 7).
However, another important dimension where new technology can play an important role, and be beneficial in a very topical way, is risk reduction. You will need to have been in very remote parts of the world recently to be unaware of the effect that risk taking has had on global capital markets and, in turn, the impacts on people’s everyday lives. Risk management is a fundamental and key part of any endeavour, and offshore projects, like complex financial investments, are no exception.
We are continuing to devote a lot of effort to structural integrity management within Acteon, as a consequence of increasing customer demand for more intelligent systems to plan and implement inspection and remediation programmes. 2H Offshore continues its endeavours to expand its capability and services in the riser and subsea equipment market.
Applying new technology is sometimes viewed as potentially increasing risk. There can be an understandable reluctance to be the first to try something new. However, if the risks are understood and well managed, risk reductions can result. The key here is “well managed.”
I would also like to mention the formation of InterAct, again in response to market demands, this time for improved early-stage project analysis, planning and integration services, but supported by detailed skill and knowledge of field methodologies and operations. The article on page 9 gives a flavour of the capability we are building in this area, with the focus on three target applications: field development, subsea installation and decommissioning. RICHARD HIGHAM GROUP CHIEF EXECUTIVE, ACTEON
Hopefully, the editorial in this issue of S2S will provoke your interest, in which case we would be delighted to hear where we could help. There is no risk involved in making a call. Our different viewpoint might provide you with a solution. KEVIN BURTON VICE PRESIDENT, TECHNOLOGY, ACTEON
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The customer service model that we have developed in Acteon often calls for group companies to work together. This is demonstrated by the North Sea Ettrick field development project in which we were recently involved (page 14). Trident Offshore led the Acteon contribution to this technically challenging turret buoy installation exercise. In this project, the client was able to deploy a more cost-effective anchor handling vessel for installation of the mooring system, rather than a conventional large construction vessel.
Risk can also be mitigated, while simultaneously reducing costs, by using proven technology in novel ways. This fresh-thinking approach is typical of the way Acteon companies do business and optimise benefits for their clients. Several features in this issue cover these points, for example, structural integrity management; managing combinations of proven technology from various Acteon companies; and the management skills of InterAct.
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news Subsea partnership ensures asset protection When the thermally sprayed aluminium (TSA) protective coatings of three wells in the Gulf of Mexico were found to have suffered degradation, 2H Offshore was enlisted to find a solution. 2H designed three retrofit sacrificial anode cathodic protection systems for the wells and managed the hardware procurement. The company then worked with subsea mooring specialist InterMoor, which provided the deck crew and the winch operators for the project, on installing the systems.
The installation operation was performed from an external anchorhandling towing and supply vessel. Using dynamic positioning, the anode sleds were lowered by a winch over the stern roller and manoeuvred into place in approximately 1370 m of water to target locations less than 15 m from the producing wellheads. The design of the retrofit anode sled system was developed to satisfy the strict installation constraints. Each anode sled consists of a structural frame supporting 1090 kg of sacrificial
aluminium. Special clamps adapted for remotely operated vehicles connect the sleds to the wellheads through heavyduty electric cables. The retrofit system will provide cathodic protection to the conductor, the wellhead and the riser for 20 years. Michael Ritchie, engineer in charge of the project, says, “This project demonstrates that 2H is capable of designing a custom product that is outside of its normal riser design and integrity monitoring work, procuring that product and seeing it through to installation.”
New yard caters for clients’ needs With client convenience in mind, InterMoor prioritised the transfer of Diamond Offshore’s equipment into its new Fourchon, Louisiana, USA, yard during late 2007. Having operated in the facility since then, Diamond is now purchasing an office unit to be located on the site.
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Further to this, InterMoor has reached an agreement with safety specialist Halo, LLC to operate a full rigging shop and a testbed facility in the yard.
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InterMoor’s 25-acre facility includes more than 360 m of bulkhead waterfront dock space, a warehouse, an office and a training centre. The facility comes complete with three cranes to support the yard and provide heavy-lift services, including a new ringer crane that offers a maximum lift capacity of 880 t and has a reach capability of 375 ft, which enables
a large area of the yard to be used for heavy storage. Having been erected and with the boom sections being finalised, the new crane is awaiting certification before it becomes fully operational. Kirk Trosclair, InterMoor operations manager at the Fourchon yard, says, “All aspects of this new facility have been designed with the client’s perspective in mind. Time is money, and the more efficient our dockside services become, the more valuable we are to our clients. Our core business of mooring services will not change, but the 880-t crane will open new opportunities in heavy lift and storage and will enable us to mobilise mooring equipment faster, thus removing the need to shuffle boats around.”
“Time is money,
and the more efficient our dockside services become, the more valuable we are to our clients.”
Groundbreaking environmental monitoring system ready for shipment 2H Offshore has completed the design and supply of a pioneering environmental monitoring system for BP. The project is based on a concept developed by Oceanlab, part of the University of Aberdeen, which is also supplying specialist environmental monitoring instrumentation. Designed and project-managed by 2H in Woking, the deep-ocean environmental long-term observatory system (DELOS) structure was fabricated at Exel Composites in Runcorn, UK, and assembled for final testing in Aberdeen. It has now been shipped to Norway, where preparations are being made to install it offshore Angola. DELOS will be used to conduct biological research in the poorly understood deepocean environments. The system is a subsea structure installed on the seabed with retrievable modules onto which a range of
scientific instrumentation can be mounted. Several innovative technologies have been used, including glass-fibre construction to reduce the environmental impact on the seabed and a suite of environmental monitoring equipment controlled by lowpower data-logging systems. The system had to be built entirely from glass-fibre-reinforced plastic composite and super-duplex steel to avoid the need for corrosion protection systems, which might have contaminated the sensitive environmental research. Because this is the first long-term deepwater application of a composite structure, 2H had to work with the National Physical Laboratory to prove that the materials would be structurally sound after 25 years in ultra-deepwater conditions.
compensate for the inclination of the docking station on the seabed. 2H addressed this by creating two cages, an outer frame that fits in the docking station and an inner frame mounted on an adjustable lever. BP will install two DELOS units offshore Angola at water depths close to 1500 m. One unit will be placed within 50 m of a working wellhead and will provide nearfield measurements, whereas the other will be placed 8 km from drilling operations. This will give scientists an indication of the effects of drilling and subsea production activities on marine environments. Both systems are intended to operate for 25 years with 6-monthly services by remotely operated vehicle to retrieve and reinstall the instrumentation modules. The initial installation will take place in 2008.
Further challenges included installing a facility to adjust the modules to within ±2° to
Merger boosts Team offering
Established for many years now, the Aquatic manpower division has over 250 contractors currently working in the field. The division is located in Aberdeen, UK, and Doha, Qatar, and serves the UK, the Middle East and beyond. The Doha office provides ground-level production
forces and has vast experience of the logistics involved in providing work crews, whereas TEAM in the UK focuses on drilling personnel and supervisors. The merger of two complementary divisions of the group will effectively enable TEAM to cross-sell its services worldwide; the Doha office has already taken advantage of its new resources in providing personnel for a Qatari drilling contractor. With a view to breaking into the markets in UAE and Kuwait, as well as into the offshore construction industry, TEAM is concentrating
its immediate focus on building upon current contracts to introduce UK-based services, such as drilling staff, into the Middle East. George Highmoor, general manager of TEAM Energy Resources, said, “There can be no doubt as to the value of this new addition. Before the merger, TEAM in the UK turned over £15 million a year. With the incorporation of the new division, we have increased that to £30 million. We have charged our manager in Qatar to find more business now that he has the additional UK drilling resources.”
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Having gained from the incorporation of Aquatic’s manpower division, UK-based TEAM Energy Resources is set to make further inroads into the international personnel market, as well as increasing the range of disciplines on its database.
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CASIM advances InterMoor continues to make advances with its compensated anchor-handler subsea installation method (CASIM). Initial engineering work has begun to develop a modified depth compensator for tackling the installation of seabed equipment such as trees and manifolds in deepwater environments. The new system will be based on a nitrogen-overhydraulic single cylinder with multiple accumulators that act as a subsea heave compensator. These new units will be depth compensated and adjustable subsea. Should conditions change during an operation, the desired compensation can be maintained through pressure adjustments via the panel of a remotely
operated vehicle. The new system will also feature hydraulic circuits for controlling the stroke out before entering the water. A 20-t prototype is currently in development for testing, after which two fully operational 75-t models will be built. Brent Boyce, subsea installation manager at InterMoor, says, “We are developing these new compensators to fit the growing needs of our customers. The new demands and challenges push us to improve on the services we already provide.� The all-inclusive CASIM service package has been widely acclaimed since it was first demonstrated in 2006, and it continues to be in strong demand.
rapid responses mean efficient operations for petrom omv
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CIS has recently provided substantial savings on both costs and rig time for Petrom OMV. In early 2007, CIS was approached by Grup Servicii Petroliere SA, a drilling contractor working for Petrom in Romania, to supply an S-90 hydrohammer package on board the Saturn rig following the failure of a diesel hammer. The hammer was used to install a 30-in. conductor and provide cold-cutting services to the jackup rig.
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The successful completion and the rig time saved encouraged Petrom OMV to award CIS a three-year contract covering all its conductor installations in the Black Sea region. To date, the company has installed seven conductors, all without any down time, accidents or incidents.
Through its strategic positioning of hammers at locations across the world, CIS was able to dispatch the new hammer the day following the request.
For one such operation in November 2007, CIS received an urgent request to supply a 30- Ă— 1.5-in. directional drive shoe for a conductor installation on board the Jupiter rig. The rig was positioned over a platform, and there were concerns that the new conductor might collide with an existing one driven across the open conductor slot.
The installation work was completed in textbook fashion without needing a cleanout run, which had normally been required on previous installations.
The machine shop completed the drive shoe overnight, and it was airfreighted the following day and then transported out to the rig.
CIS then supervised the welding of the shoe onto the end of a 40-ft joint, before it was spudded into the seabed. This work was performed at slack tide to avoid interference from the elements and ensure a true direction. CIS plans to perform at least three more deviated-drive operations during 2008.
Re-engineering the conductor installation process An innovative subsea installation technique developed by InterMoor has helped Shell Brasil Ltda to prove a new technology for conductor installation. The scope of work performed by InterMoor in the Parque das Conchas fields in Brazil’s Espirito Santo basin included installing eleven 36-in × 50-m drilling conductors, two templates, a guide for the caissons and a foundation for the artificial gas lift manifold at water depths of 1600–1800 m. Six 48-in. × 60-m caissons were installed and driven through the template. InterMoor’s work involved welding the conductor sections and using a transport-and-launch barge to carry the conductors out to the site. This was a bespoke barge manufactured to a tight timescale and included an InterMoor-designed conductor side-launch system for keelhauling the conductors to the anchor-handling vessel (AHV). To maximise control during the installation of the conductors from the AHV, InterMoor applied its compensated anchor-handler subsea installation method (CASIM). This included performing dynamic lowering analyses on the conductors and the hammer to be used, and conductor driving analysis and procedures. As part of the CASIM service package, InterMoor also supplied two of its 6-m heave-compensation devices: single-unit cylinders that act as shock absorbers. These reduce motion and line tension spikes by behaving as soft, dampened springs applied in series with the much stiffer wire lowering system.
For the hammer, InterMoor turned to MENCK, as it is the only supplier of deepwater hammer systems. The company selected the MHU-270T deepwater hydraulic hammer, which has a driving energy of 270 kJ (at a water depth of 1000 m) combined with MENCK’s girdle-type electrohydraulic power pack. Generating hydraulic power at depth, rather than at the surface, helps to minimise the hydraulic hose length and reduces energy losses. This is the only practical method at these water depths. It also reduces environmental risks, as hydraulic fluids do not have to be pumped over long distances. In addition, the system ran on just 1400 L of a synthetic oil that biodegrades within 14 days. The project was a major undertaking with many unknowns at the outset. The combination of onshore requirements before the offshore operations could start proved to be the biggest hurdle. However, the offshore phase was a success: all the conductors and the two templates for the gas lift manifold were installed from the AHV between Q4 2007 and Q1 2008. John Cook, drilling manager, Shell Brasil, says, “The subsea hammering concept was particularly beneficial for the 48-in. caissons in the gas-lift-manifold templates. There was really no other installation method available that would give us the accuracies needed for the final conductor height.” John Riggs, managing director, InterMoor do Brasil, points out that InterMoor’s novel approach created valuable project management benefits: “By using an AHV, we were able to keep the conductor installation activity off the schedule of the drilling rig. In addition, it meant that Shell knew the exact positions of the wells before the rig’s arrival so that the detailed rigid jumper and flowline work could be performed in advance.” The concept of pre-installing conductors off the drilling rig’s critical path, although not problem free, was demonstrated to be feasible in water depths in excess of 1800 m. The main obstacle to the project was weather-related downtime in deploying the subsea hammer and the remotely operated vehicle, which was essential for the hammer deployment and installation process. The lengthy mobilisation and demobilisation times required for the hammer and its associated equipment were also major contributors to the overall project time.
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Shell approached InterMoor because it was seeking ways to make the project as efficient as possible.
This was a concept-proving project that showed the technique to have merit and one that could benefit larger-scale projects in less onerous operating conditions.
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“This is an environment in which cost is paramount, so service providers must leverage their experience to avoid or at least optimise the use of expensive repair and maintenance equipment.�
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Responding to the challenges of hurricane-damaged structures When hurricanes Katrina and Rita thundered through the Gulf of Mexico in 2005, they had an impact on 3050 platforms. While most structures performed adequately, many suffered major damage above or below water. Damage to offshore platforms had been relatively uncommon before the two powerful hurricanes struck, so S2S talked to Tom Kennedy, InterAct PMTI’s president, about the engineering challenges posed by repairing or decommissioning the damaged wells and production facilities.
InterAct PMTI mobilised on a 200-class lift boat. The planned methodology involved removing the top section of caisson down to the mudline and then jetting down to the targeted 8 m using a submersible pump. To mitigate the risk of caveins, the hole had to be sloped to a diameter of around 24 m. However, the pipe at 8 m still did not have sufficient integrity. “So we had to keep jetting,” says Kennedy. “At about 9 m, cave-ins became a major issue. When we had overcome those, we eventually found straight pipe at 12.5 m – you can imagine the size of the hole!”
Having located round, straight pipe, Kennedy’s team was able to jet down the cofferdam enclosure that would provide the dry work environment, make a cut on the caisson and move the 9-m tall cofferdam into position. The team made two cuts on the conductor to prepare it for the overshot, and installed a centraliser around the conductor before installing a 72-in. caisson around the 36-in. conductor. The well could then be He adds, “It is often impossible to obtain vital data on the field tied back to surface. conditions in advance; therefore, teams have to be nimble so This project illustrates the challenges posed by many of the that they can take an alternative approach if the need arises Gulf of Mexico’s hurricane-damaged structures, which are as the project develops.” frequently bent below the mudline. Regardless of whether Kennedy cites the example of a recent initiative to bring a the operator plans to bring the well back on production or to damaged 36-in. caisson back on production in the Gulf of plug and abandon it, the service provider has to get below the Mexico. The simple free-standing caisson (which supports a bend and find straight pipe that has integrity. Projects based single well completion with a minimal deck and is tied back on incorrect assumptions can incur major cost overruns. to surface facilities) was leaning at 52°, but it was not on the Says Kennedy, “During the planning stage, it is impossible to seabed and the wellhead was still showing. The water depth pinpoint where a conductor is damaged. And there is no science was 12 m. that can predict this to a high degree of accuracy; we have The field operator was keen to get the well back into production seen everything from platforms falling down on themselves because abundant oil reserves remained. InterAct PMTI’s role was to platforms being twisted. InterAct PMTI’s experience shows that, although some valuable engineering studies and analyses to remove the leaning structure, jet below the mudline and locate can be performed in advance, essentially the team must straight pipe so that the conductor could be tied back to surface. be prepared to respond cost-efficiently to the situation that Despite comprehensive upfront planning, Kennedy expected presents itself during project execution.” the crew to have to think on its feet when it was offshore. The organisation’s engineering studies and finite element and soil analyses suggested that the conductor was bent at a point 8 m below the mudline. However, it was impossible to confirm this. According to Kennedy the plan was: “Let us go out and see what we have. If we are correct in all our assumptions, then here is your procedure. But if we are not, then we are prepared to adjust it as we go.”
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“Increasingly, our role is about devising solutions to problems that have perhaps never been faced before,” says Kennedy, who has more than 30 years of experience in the oil and gas industry. “This is an environment in which cost is paramount, so service providers must leverage their experience to avoid or at least optimise the use of expensive repair and maintenance equipment.”
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GAP analysis 2H has worked closely with Single Buoy Moorings, Inc. (SBM) to deliver a novel transfer pipeline system for Murphy Sabah Oil Company’s Kikeh field development Assume your aim is to transfer production fluids from a spar platform moored in deep water to a floating production, storage and offloading vessel (FPSO) located 1.6 km away. It seems somewhat perverse to take these fluids from the spar, down a kilometre or more to the ocean floor in a riser, then through a seabed pipeline and finally up to the FPSO via a second extended riser. However, this is the normal way of doing it – or it has been. Murphy Sabah Oil is bucking the trend in its Kikeh field development, situated in 1350 m of water off the coast of Malaysia. In this case, the transfer of fluids in four fluid-transfer lines (FTL) between the two floating structures will use a gravityactuated pipeline (GAP) system some 1300 m long and suspended approximately 200 m beneath the surface of the sea. The FTL GAP concept, which was invented and patented by SBM, involves a neutrally buoyant bundle of steel pipes supported and tensioned by tether chains and weights linking it to the two floating facilities.
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Clearly, a shorter pipeline than normal is needed, which saves a significant amount of money. And, because the produced oil does not have to travel down to the very cold seabed, the insulation can be reduced without problems connected with hydrate formation and waxing arising. The third major
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SBM built the Kikeh FTL GAP at a specially selected site at Bintulu, eastern Malaysia. Its design permits considerable deflection of the pipe bundle. While the towheads will remain at a depth of 200 m, the central portion of the FTL GAP will be at a depth ranging between 70 and 300 m below the sea’s surface. The profile that the FTL GAP takes up will be determined by the weight of the production fluids in the FTLs, which will vary as the fluid composition changes.
advantage of the concept is that the loads imposed on both the spar and the FPSO are reduced, certainly compared with those involved if steel catenary risers were to be used. The FTL GAP concept is undoubtedly elegant, but it is one that requires highly specialised engineering skills to translate it into a practical and confidence-inspiring design. 2H Offshore has been working closely with SBM for almost two years to do just that. Soon after the two companies began to look at the design together, it was realised that ensuring the Kikeh FTL GAP had an adequate fatigue life, and then clearly demonstrating this, was going to present a serious challenge. An early engineering analysis indicated that a structure based on the outline design would have a fatigue life of the order of 200 years – not long enough for such a critical application, especially when the estimate did not take account of possible fatigue damage during tow-out and installation. Yann Helle, 2H project manager, says, “From our experience, we believed that to increase the fatigue life of the FTL GAP, we needed to concentrate on the first-order fatigue induced in the structure by wave action on the FPSO.” As a priority, Helle, his team and SBM set out to find a way of decoupling the motion of the FPSO from the FTL GAP. (The problem is not so acute at the connection between the spar and the FTL GAP because the movements of the spar are not as extreme as those of the FPSO.) The solution adopted by SBM involved installing air cans at the FPSO end of the FTL GAP to provide extra buoyancy. It was also decided to use a
heavier chain between the FPSO and the FTL GAP so that the link between the two would take the form of a catenary. An enormous amount of detailed analysis by 2H was necessary to prove the effectiveness of the modification before its approval by all the relevant parties. Significantly, the predicted fatigue life of the new design is around 1300 years. 2H also provided input to the procedures for launching and towing the FTL GAP during installation in order to reduce stresses on the structure and avoid reducing its fatigue life even before it was put into service. Interestingly, the 2H engineering analysis also offered assurance that the bulkheads built into the carrier pipe at regular intervals to resist buckling propagation along the pipe would be up to the task. This was valuable, as it meant SBM was able to avoid expensive practical tests to verify this aspect of the FTL GAP’s design. Fabrication of the Kikeh FTL GAP started at Bintulu in eastern Malaysia in mid-2006, and the structure was launched and towed out to the field in May 2007. There has been an unusually constructive relationship between SBM and 2H throughout the project. “SBM is a world leader in critical areas of FPSO design and has a tremendous grasp of the needs of the deepwater market,” says Helle. “We can take pride from having used our expertise in riser analysis and engineering to help SBM deliver this groundbreaking project – this is the first pipeline system of its kind in the world.”
A 3D CAD-generated drawing of the towhead at the FPSO end of the FTL GAP showing the air-can arrangement.
GAP will have 18 stand-alone INTEGRIpod motion loggers fitted along its length and two pressure sensors. It is satisfying to realise that as well as verifying that this FTL GAP responds in accordance with the engineering assumptions made at the design stage, the data collected will aid the design of future novel pipeline systems of this kind.
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Under a separate direct contract with Murphy Sabah Oil, 2H is providing a monitoring system for the FTL system. The FTL
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Rising to the fore New products company widens choice for riser hardware Industry journalist Terry Knott talks to Steve Hatton, managing director, 2H Offshore, about new Acteon company Subsea Riser Products Acteon has launched a new company in the seabed-to-surface market to provide clients with a range of innovative riser hardware solutions. Inaugurated in February, Subsea Riser Products (SRP) is doing just as its name suggests – designing and supplying riser components – but doing so with a keen focus on technology, costs, schedules and local content, which promises to give the company an advantage in this highly competitive market sector. This move has been spearheaded by Acteon group company 2H Offshore, a recognised leader in subsea riser systems design, and comes in response to Acteon’s desire to grow and diversify its riser-related business by introducing innovative technology into the market. “For riser system development, 2H designs not only the riser pipe, but also produces the specifications for all of the associated components from the seabed upwards,” says Steve Hatton, managing director of 2H. “Typically, these components will include riser joints, connectors, tensioners, buoyancy modules, coatings and handling tools, all integrated into a complete riser system. “However, our contractual relationships do not normally extend to supplying the hardware items, and these are sourced by the client. But over years of designing complete riser systems, we have learned where there are opportunities for improvement in the hardware market, and have developed our own technology ideas for filling these gaps. Those ideas have now been transplanted into SRP, along with other relevant innovations selected from around the Acteon group.” Although the initial product design ideas have come from within the group, SRP will operate independently of the other Acteon companies, and must be seen to do so, Hatton emphasises.
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“The riser configurations designed by 2H will not be detailed to favour products from SRP, and, just as we do now, the key riser components will have a functional specification, which will enable the client to issue a competitive requisition package for suppliers to bid against.”
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Acteon believes that this balance of independence can be achieved, as the industry already supports several companies that have both design and supply sides in their groups without compromising independence. The Acteon move has also received the endorsement of several client companies, which have expressed support for SRP’s launch.
SRP, based in Woking, UK, is now building its in-house capabilities around an engineering team transferred from Precision Engineering Design, a local specialist mechanical design company that has worked closely with 2H for some years and was recently acquired by Acteon. A strategic decision taken in establishing SRP was for the company not to have its own manufacturing capability. In many of the world’s deepwater regions where major development projects are located, for example, offshore Angola and Brazil, there is increasing demand for local content in the supply of equipment. Several of the new products offered by SRP lend themselves well to local manufacture. As SRP is not tied to one manufacturing base, the company has significant flexibility in where it fabricates its products, thereby gaining a competitive advantage in regions where local content is an important driver in supplier selection. Discussions have already started with local companies, for example, in Angola, that are capable of providing the skills and services, such as welding, machining and pressure and non-destructive testing, necessary to manufacture SRP’s products. Among these products are three innovations transferred from 2H, each an alternative to conventional riser components already in the marketplace and offering advantages. Shrink-fit is a patented design and method for attaching a flange or other connector to the end of a pipe joint without welding. One application, which is due to make its debut for North Sea clients next year, is for high-pressure drilling risers. In conventional practice, high reservoir pressure is handled by a blowout preventer (BOP) at the seabed, which enables the drilling riser to the surface to be designed for lower pressures. If the riser were to be designed for high pressures (over 10,000 psi), the pipe joints would have 40–70-mm thick walls, which would present difficulties in ensuring integrity and fatigue performance when welding flanges onto the pipe joints. In contrast, the Shrink-fit technique enables purpose-designed bolted flanges to be attached to high-strength, thinner-walled steel pipe joints – without welding. The result is a lighter-weight, high-pressure riser with its BOP located more accessibly on the drilling rig – an attraction for high-pressure offshore fields. The Shrink-fit method is also targeting taper and tension joints, the pipe joint sections at the top and bottom of risers that are tapered to control stresses and meet strength requirements.
SRP HAS a competitive advantage in regions where local content is an important driver in supplier selection.
A second new proprietary product available through SRP is LinkLatch. The device is an articulated latch for attaching the base of a freestanding riser to a pile in the seabed, thus providing a secure connection while giving a degree of movement between the two. Currently, the alternative hardware available for this duty incorporates sophisticated elastomeric elements designed for high loads, which are expensive and require long manufacturing lead times, perhaps 18 months. Link-Latch is a simpler design and is based on two large chain links held in a two-part housing joined by a bellows rated for a 200-t operational load. The net result is a compact connection with
multidirectional movement that is cheaper and quicker to manufacture around the offshore industry. The third new component, Trunnion-Latch, is a high-capacity connection purpose-designed for attaching a buoyancy air can to the top of a free-standing riser. The compact latch has integral water-lubricated PTFE bearings, with a 1000-t axial load operating capacity and the ability to deflect by up to 25Âş. Trunnion-Latch is also designed for ease of fabrication from plate and bar material, which cuts down lead times and offers flexibility in manufacturing locations. Innovative SRP products such as these, and many others, will provide Acteon clients with the reductions in cost and schedule they frequently seek.
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Taper joints, 10–12 m long, are normally machined from a solid forged bar, including the flanges, which requires complex heat treatment and has an expensive price tag. Using Shrinkfit flanges means that a smaller diameter bar can be used to produce the tapered joint section and the flanges can be added afterwards, which will significantly reduce the fabrication costs.
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Submerged turret buoy mooring Six Acteon companies contribute to a successful operation
While many people were still enjoying their winter holidays, a 450-t submerged turret buoy was being installed in the central North Sea. The 26 December installation was part of Nexen Petroleum U.K. Limited’s development of Ettrick field. Six Acteon companies were involved in the mooring operation, principally Trident Offshore, which worked with field development contractor Saipem UK, Sonsub Division (Sonsub), but with important contributions from sister companies 2H Offshore, InterMoor, Aquatic, IMS and Seatronics.
For the third phase, the conical turret buoy, which is 11 m high and 11 m in diameter, was prepared by Sonsub and Trident at the Port of Invergordon, UK, before being towed to Ettrick field. In port, the buoy’s ballast system was commissioned, and the nine 148-m-plus JSS mooring cables were spooled off using an Aquatic AQPR7A powered-reel drive system and attached to Nexen Petroleum U.K. is developing blocks the buoy in two sections. 20/2a and 20/3a in the Ettrick oil field in just over 100 m of water with a subsea Large buoy systems are typically installed tieback to the Aoka Mizu floating production, using large construction vessels. However, storage and offloading (FPSO) vessel. Mid- in this case, a single anchor-handling water-arch, lazy-S and steep-wave riser and vessel was used for the mooring system umbilical systems will be connected to the installation and hook-up operations. This FPSO through the detachable submerged meant that the buoy had to be launched turret buoy. Three sets of three mooring and towed with the top sections of its prelines, consisting of chain and JSS cable, installed JSS cables suspended to tugs. To fastened to driven piles, now hold the buoy avoid cable damage through dragging on the seabed, IMS provided buoyancy modules in place. fitted with acoustic releases supplied by The buoy was installed in four phases. In Seatronics. The buoyancy modules were September 2007, piles were driven into the released once the buoy was in deeper water, seabed by Sonsub. Then chain sections were and the system was towed to its installation offloaded by Trident/Sonsub, ranged and location. The assembly and load-out of the inspected by IMS (ChainCo), and cut into buoy and its moorings required four towing 30-m lengths. The chains were extended vessels and several shore-based cranes, from the piles, each ended with a female including one of 1200-t capacity. subsea connector that was left supported in a frame ready for the second phase.
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The work had several technically challenging aspects, including towing the buoy with nine pre-attached, 148-m jacketed spiral strand (JSS) mooring cables and the need to complete the final three hookup connections subsea. This is the first installation of a permanent system in the North Sea using subsea connectors.
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During the second phase, the remainder of the bottom chain section of each line was deployed under Trident’s instruction and supervision and a JSS cable was attached to its end. The JSS cables were installed using an Aquatic AQPR2 powered-reel drive system. The mooring legs were tensioned using a tandem vessel pull to about 450 t with modified shackles provided by IMS. The final length of each chain was calculated, and the chains were cut and laid on the seabed ready for hook up to the JSS cables, which were already connected to the buoy.
The buoy was hooked up in the final phase by offsetting it to enable two of the three sets of mooring lines to be attached. The buoy was then towed onto location and submerged to provide enough slack in the system to enable the third set of lines to be connected using the subsea connectors. David Cobb, Trident projects manager, says, “I believe that this is the first example of towing a buoy of this type with such a large quantity of pre-attached spiral strand cable. It is also the first permanent system to be installed in the North Sea using subsea connectors. The project used 12 subsea connectors.” With Sonsub’s direction, Trident developed the procedures used for towing out, installing and tensioning the mooring lines and the buoy, and also provided equipment inspection and offshore supervision. Other Acteon companies were involved too, which gave the customer the advantages of Acteon’s comprehensive in-house capabilities. Trident brought in 2H Offshore for tow-out and hook-up analysis and drew on specialist expertise from InterMoor. Aquatic supplied personnel and two powered-reel systems. “Aquatic also assisted Trident in developing the spooling procedures, which were well received by Sonsub. The company hired Aquatic directly, but was able to take advantage of our close relationships within the Acteon group,” says Cobb. “The operation involved up to five vessels, a remotely operated vehicle and people from several organisations,” continues Cobb. “We developed a great working relationship with the Sonsub team, which enabled us to work efficiently during the offshore operations. I am pleased that the installation was such a success.”
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“I believe that this is the first example of towing a buoy of this type with such a large quantity of preattached spiral strand cable. It is also the first permanent system to be installed in the North Sea using subsea connectors. The project used 12 subsea connectors.”
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Acteon has an outstanding portfolio of complementary products and services for the subsea marketplace. The experience shared by Acteon companies opens up the opportunity for a different approach to subsea operations and services.