World’s largest riser support structure installed with unique EPCI solution

The Ichthys Liquefied Natural Gas (LNG) Project is one of the world’s largest, most complex LNG developments, scheduled to begin production in 2018. Operated by INPEX, the project is designed to provide approximately 10% of Japan’s LNG needs. 

In one of the world’s largest LNG projects, with the biggest subsea scope ever undertaken in Australian waters (Fig. 1), a multitude of contractors have been involved, including McDermott, as one of the largest contractors undertaking the subsea works.

Fig. 1. McDermott’s Lay Vessel 108 (LV 108) is shown in front of the Ichthys Explorer Central Processing Facility (CPF), part of the biggest subsea project ever undertaken off the coast of Australia.

 
For the past six years, McDermott has been delivering an engineering, procurement, construction and installation (EPCI) solution for the subsea umbilical, riser, flowline (SURF) system. Due to its size (Table 1), the Ichthys project has set many industry firsts, and overcome many challenging technical and installation-related hurdles required of a world-class development of this magnitude. 

 
BACKGROUND 

Sitting about 137 mi offshore Western Australia, in an average water depth of 820 ft, lies INPEX’s 309-mi² Ichthys field. Gas from five drill centers is gathered through 87 mi of infield pipelines and sent to the Central Processing Facility (CPF) via one of the world’s largest, most complex flexible riser systems, Fig. 2. 

Fig. 2. Gas from five drill centers, spread across the field, is routed through infield pipelines and directed toward one of the world’s largest, most complex flexible riser systems.

 
The lifted gas is piped over 553 mi to the onshore liquefaction gas plant in Darwin, Northern Territory. There, up to approximately 8.9 million tons of LNG and 1.6 million tons of LPG are to be processed and shipped annually, with a further 100,000 bcpd recovered from the FPSO facility, when production is at its peak.

In 2012, McDermott was awarded the offshore SURF EPCI scope. The geographical location required a technical solution developed around unique, challenging soils in seismically active zones, with conditions of sour service, high pressure (371 bar) and high temperature (150°C). This, coupled with the 40-year design life and 10,000-year cyclone survival criteria, as well as hook-up to the world’s largest semi-submersible (CPF), required a number of industry firsts.

The Ichthys project represents Japan’s largest overseas investment, to date. According to INPEX, Ichthys is one of the biggest gas-and-condensate-rich discoveries offshore Australia.

 DETAILED ENGINEERING

The design of the subsea assets and infrastructure required the expenditure of over 500,000 man-hours from the contractor’s engineering centers around the world. The company’s fabrication yards on Indonesia’s Batam Island, and in Singapore, were selected as key work locations, based on their proximity to Ichthys field, offshore Western Australia, Fig. 3. The high-end conceptual engineering was executed in Perth, while detailed engineering was completed in Singapore, with support from other centers around the world. 

Fig. 3. The locations for engineering design were selected on the basis of their proximity to Ichthys field, as well as McDermott’s Batam Island fabrication yard in northern Indonesia (as shown in this image).

 
Positioned within the “cyclone alley” of the Browse basin, the Ichthys project required a solution that could comfortably withstand the rough weather conditions and survive storms occurring “once every 10,000 years.” Although designing the individual subsea assets to these criteria was not beyond industry standards, the combined scope and scale is what set Ichthys apart from all other floating production facility projects, Fig. 4. 

Fig. 4. Shown here is the Gas Export Riser Base (GERB) Module 3 that McDermott installed as part of its SURF work.

 
The engineering solution required the management of complex interfaces with the Ichthys Explorer CPF, Ichthys Venturer FPSO, Subsea Production System (SPS) and Gas Export Pipeline. Accordingly, complex interface management was infused throughout the lifecycle of the project, from the first engineering calculation to the final installation and pre-commissioning campaigns.

GLOBAL SUPPLY CHAIN

The sheer magnitude of the Ichthys project, combined with the unique durability requirements— in particular, the 40-year design life—resulted in a number of challenges. Extensive in-field equipment was procured from vendors across multiple continents, demanding a new level of excellence in supply chain management. To ensure that product quality was maintained, the contractor developed a robust package management approach, drawing upon the expertise of quality assurance engineers, subject-matter experts, third-party certification, and project controls, to ensure delivery to specification, schedule and budget.

Major components procured for the project included:

• More than 100 rigid and flexible horizontal connection and vertical connection systems. 
• Roughly 36 mi of production controls, high-voltage power and communications umbilicals, and 31 steel flying leads.
• The largest order, ever, of diver-less bend stiffener connectors (42) that required zero ROV intervention.
• A group of 44 flexibles that totaled more than 25.5 mi and included project qualification for the 12-in. production riser, and 10-in. smooth-bore gas export risers.
• A 267-valve assortment, ranging in size from 2 to 42 in., which included the world’s first and largest (42-in.) forged body subsea ball valves, Fig. 5. 
• Nearly 40 mi of seamless carbon steel, seam-welded duplex, and metallurgically clad pipes and 300 induction bends. 

Fig. 5. A group of 267 valves, ranging in size from 2 to 42 in., which included the world’s first and largest (42-in.) forged body subsea ball valves.

 
McDermott deployed a large team of project personnel to many of the key manufacturing facilities, including sub-suppliers that were making subsea components, so that they could deliver project certainty. A multi-tiered package management process helped to maintain the overall project schedule. 

CONSTRUCTION AND FABRICATION

Over 12 million Lost Time Incident (LTI)-free man-hours were executed successfully in the completion of the 26,000 MT of subsea structures fabricated in Indonesia at the contractor’s Batam Island fabrication yard. The scope included the riser support structure, gas export riser bases, production riser bases, MEG distribution manifold, flowline end terminations, in-line tees, mid-depth buoys, flexible pipe connection assemblies, spools and well jumpers.  

The in-house fabrication team focused on proactive management to mitigate risks that are typically inherent with the high level of external interfaces. Early engagement of the fabrication team ensured that sufficient levels of constructability inputs were incorporated into the engineering and procurement phases, Fig. 6. 

Fig. 6. Early engagement of the fabrication team ensured that sufficient levels of constructability inputs were incorporated into the engineering and procurement phases.

 
Similarly, the cumulative 2.5 years of factory acceptance testing, system integration testing and mock-up testing, permitted by such in-house facilities, significantly reduced the offshore risk of failure and downtime during the installation campaigns.

WORLD’S LARGEST RISER SUPPORT STRUCTURE 

Of the many subsea structures built, the Riser Support Structure (RSS, Fig. 7), was particularly interesting and more challenging. At the time of installation, the weight of 8,500 MT made it the largest subsea structure ever installed.

Fig. 7. Of the many components built as part of the SURF, one of the most interesting and challenging was the RSS (shown here), which weighed more than 8,500 MT and stood 361 ft tall in 820 ft of water. The sheer number of flexible risers, and field location, required a number of innovative engineering solutions.

 
To aid installation of the 361-ft-tall RSS tower, two 1,000-MT temporary buoyancy tanks were used. This improved both the in-field barge launch and the ability of the installation vessel crane to maneuver and lower it into place. 

The RSS arch, which measures 410 ft in length and is 46 ft tall, was designed to accommodate 25 flexible pipeline and umbilical risers. Installed separately, the arch was connected to the tower structure through grouted connections at multiple stabbing locations.

The field’s susceptibility to cyclones and seismic activity, along with a challenging mixture of sandy and silty carbonate sands, required a uniquely designed base (Suction Skirt Gravity Base Foundation) to be prototype-tested and installed for the project. A rectangular, doughnut-shaped, shallow skirt, comprised of multiple suction compartments with novel sliding hatches, provided the passive suction pressure required to withstand the uplift and lateral loads in extreme conditions. 

TRANSPORTATION & INSTALLATION 

The transportation and installation (T&I) campaign involved the use of three newbuild installation vessels over a four-year period. With a supply base located in Broome, Western Australia, the T&I scope of work included: 

• A pre-lay survey 
• Sleeper installation 
• Rigid pipe installation via reeled and J-lay 
• RSS and MDB installation 
• Rigid pipe J-lay
• CPF and FPSO anchor piling
• Subsea structure installation 
• CPF and FPSO mooring chain installation 
• Tie-in spools installation 
• Flexibles and umbilicals installation 
• CPF and FPSO mooring hook-up 
• Flexible riser and dynamic umbilical pull-in 
• Pre-commissioning of relevant systems.

McDermott’s DLV 2000 was used to lay umbilicals, and install the larger structures and heavier spools, including the 42-in. gas export spool, whose combined lift weight of almost 500 t makes it the largest subsea spool installed, to date.

The Lay Vessel 108 (LV 108) is the contractor’s most adaptable vessel in the fleet. It demonstrated its versatility on this project, operating in both construction, and hook-up and commissioning modes.

During the project’s first half, the LV 108 executed the installation and pre-commissioning of structures, including the lateral buckling sleepers, spool supports, concrete mattresses and smaller spools, ranging up to 7.9 in., in diameter.

The project’s second half saw the LV 108 mode-change to incorporate the Reel Drive System and Vertical Lay Tower, to carry out the installation, hook-up and commissioning of the floating facilities.

As the RSS was the key marker point in the field development, one of the project challenges was to install the RSS before the beginning of the cyclone season. Any delay in installing the RSS would have affected all the other offshore work, and would have delayed the project significantly. McDermott mobilized resources across multiple fronts and locations to stay on schedule for this project’s fast-track nature, Fig. 8. 

Fig. 8. The transportation and installation phase involved the use of three installation vessels over four years. Among the items installed by <i>DLV 2000</i> were the umbilicals.

 
As part of the T&I scope, the contractor oversaw the management of its prime subcontractor, Heerema Marine Contractors (HMC), for installation of the following by the Aegir: 87 mi of 18-, 12- and 6-in. pipelines; RSS tower and arch (8,500 MT); 49 driven piles (35,000 MT); 49 pile mooring chains (7.1 in. x 3,281 ft) and 12 subsea structures (6,000 MT). 

QHSES

The company’s commitment to quality, health, safety, environment & security (QHSES) remained the top priority within the Ichthys project. McDermott worked more than 20 million project man-hours. The project resulted in a number of QHSES leadership initiatives on a company-wide scale. Managers regularly engaged with employees to clearly understand and identify any potential issues or concerns that would impede project quality and delivery. QHSES requirements were discussed openly, to ensure that expectations were met, and the team was focused on safety, quality and employee wellness. Leadership, communication and a proactive approach to risk management were critical to achieving good QHSES results on this project.

To help ensure that everyone understood how the work would be performed, QHSES requirements were addressed at the start of each job. Particular emphasis was placed on aligning the QHSES performance of vendors and subcontractors with project values. These proactive measures resulted in exceptional performance and project delivery for the operator, Fig. 9. 

Fig. 9. McDermott, with its newbuild DLV 2000, played a key role in the successful installation and completion of the complex subsea infrastructure designed to safely, and efficiently, extract gas and condensate from Ichthys field.

 
Key resources were made available to the project teams, to ensure risks were identified early and managed effectively without compromising delivery timelines. The project brought workers from around the world together into one common safety culture. 

CONCLUSION

The INPEX-operated Ichthys LNG Project has seen the development of incredibly advanced offshore facilities and state-of-the art onshore infrastructure, joined by one of the longest subsea pipelines in the world. “It is a challenging, complex project with many different moving parts,” said Mr. Louis Bon, INPEX managing director for the project. “The project was completed safely to the highest industry standards, with a much higher-than-usual design life of 40 years.” 

With first gas estimated this year, this mega-SURF used client-contractor collaboration and had multiple engineering marvels while ensuring the highest standards for QHSES. McDermott has executed an engineering feat, in ensuring the delivery of more than 80,000 t of equipment on the seabed, to transport the gas from various wells to one of the industry’s largest production facilities.