cheduled to come online in the third quarter of 2009, Tahiti will start with six wells. Within several months of initial production, output from the Tahiti Spar platform is expected to increase to the facility capacity of 125,000 barrels of oil per day. Based on J. Rays high quality welding procedures,

Chevron awarded J. Ray McDermott a contract on this project in 2005. The scope of work included transportation and installation of subsea flowlines for the Tahiti project; two six-inch and four nine-inch wet insulated flowlines and Steel Catenary Risers (SCRs), and Pipeline End Terminations (PLETs). J. Ray also was awarded the recovery and hang off of two abandoned export SCRs, a 20-inch and 16-inch, and the installation of three large subsea manifolds ranging in weight from 60 to 250 tons.

riSEr rEliaBility The riser system is a critical part of deepwater field architecture its design and construction must be highly reliable, to ensure the field can safely produce for many years without interruption, said Jim Reiners, Chevrons Subsea Installation Lead Engineer for the Tahiti Project. SCRs are technically feasible and commercially efficient for reservoirs with high temperatures and pressures, but they are highly sensitive to environmental loading and fatigue. Such forces over the fields lifetime include water pressure, vessel motion, wave action and ocean currents, so SCRs must be designed and installed in a way that minimizes the damaging effects of these stresses. Manufactured from pipe sections with strict pipe-end tolerances to reduce misalignment and pipe-ends matching and/or counter bore on the ID of the pipes, SCR sections must meet high tolerance and fracture toughness requirements after field welding, explained Reiners. In order to meet demanding service requirements, welding criteria for fatigue sensitive SCRs is probably one of the most stringent in the world. J. Rays welding procedures for the offshore installation of the SCRs met or exceeded these rigorous specifications. J. Ray McDermotts proven J-Lay technique was

28 J.Ray NEWS www.jraymcdermott.com

Handle With CareHigh Quality Welding and Challenging Installation - 4,300 feet Under the Sea

The Tahiti deepwater field development in the Gulf of Mexico is one of Chevrons major growth prospects. Similar to other major deepwater fields under development, the Tahiti reservoir lies beneath a massive salt canopy that begins approximately 100 miles off the eastern tip of Louisiana and extends to the Texas coast. The high pressures and temperatures associated with reservoirs that extend to 28,000 feet below sea level, coupled with water depths ranging from 4,000 to 4,300 feet, create a significant challenge for the construction and installation of the subsea equipment necessary to enable safe and reliable production.

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numBer oF onsHore WeLds ComPLeted For tAHiti

multi-JoiNt FaCility 9-inch welds | *SCR+FSFL | 786 high spec fatigue

sensitive welds *SFL | 534 high spec flowline welds

6-inch welds | SCR+FSFL | 369 high spec fatigue sensitive welds

SFL | 270 high spec flowline welds

J-Collar SHoP 9-inch welds | SCR+FSFL | 532 high spec fatigue

sensitive welds SFL | 360 high spec flowline welds

6-inch welds SCR+FSFL | 250 high spec fatigue sensitive welds

SFL | 180 high spec flowline welds

*SCR (Steel Catenary Riser), SFL (Standard Flowline), FSFL (Fatigue-Sensitive Flowline)

ideally suited for the fatigue-sensitive SCR installation in Tahitis 4,300-foot water depth. Mounted on J. Rays dynamically positioned installation vessel, DB50, the J-lay equipment allows precise control of all operations in water depths beyond the limits of conventional moored systems. Laying SCR pipe by J-lay, at near-vertical angles significantly reduces fatigue on the quad joints, by reducing the distance of the flowline touchdown to the seafloor, explained John Danos, J. Rays Marine Operations Division Manager for Deepwater and the Americas.

FEaSiBility For multi-JoiNt FaCility With the riser installation scope awarded to J. Ray in October 2005, Chevron began discussions with J. Ray to fabricate the quad joints for the project, convinced that it was best for project schedule and quality. The quad joints required the same high-quality welds as the offshore field welds. Each quad joint comprised four 40-foot pipe joints and one forged J-Lay collar, thus the amount of welding required on the project increased five fold. At Chevrons request, J. Ray began a feasibility study to build a dedicated multi-joint fabrication facility at its Morgan City marine base in Louisiana to handle the quad-joint onshore fabrication. Simultaneously, J. Ray prepared a commercial proposal to build the facility and perform the fabrication work. Chevron awarded us the quad joint scope of work in January 2006, said Danos. By fabricating and installing both the pipeline quad joints onshore and handling the offshore J-Lay installation, we minimize the typical interfaces between fabri-cator and installer and maintain a consistent high-quality weld critical for subsea flowline installation at these depths. A welded joints fracture toughness is highly influential in the fatigue life of the joint, as it defines its resistance to failure through fracture once flaw propagation has reached a critical size. Extensive qualification to confirm weld ability and provide long-term fatigue performance in an offshore environment is vital. The welded joint fracture toughness for high-yield strength risers requires careful attention to line pipe properties and welding processes, as difficulties can arise with higher strength steels that tend to have high hardness and low fracture toughness properties. As we began construction of the multi-joint facility in January 2006, we also began construction of a J-collar workshop for the preparation, assembly and welding of the upper J-collar forging assembly to individual 40-foot pipe joints. The J-collar shop and the multi-jointing facility were designed and built in just 13 months. A commendable achievement, said Danos. To maximize productivity during construction of the multi-joint facility, two out of five quad-joint welds were performed in the J-collar shop; the J-collar was welded to the pipe section and then a 22-inch pup-section was welded to the J-collar. Subsequently, 40 percent of the required quad-joint welding was completed prior to the completion of the multi-joint facility. By late January 2007, J. Ray was running quad joints through the new multi-joint facility. All welds were Fusion Bond Epoxy coated and insulated per Chevrons requirements. Quad jointing

was completed on schedule during the last week of May 2007. At peak production, the facility completed 50 welds in a 10-hour day. Overall, we successfully completed 3,255 welds, 60% of which were critical fatigue-sensitive welds; all adhered to Chevrons stringent SCR weld acceptance criteria, said Danos. Our high-quality welds, excellent weld and material traceability of finished work, schedule certainty and superior safety record during the fabrication of the Tahiti quad joints are all measures of the success of our new multi-jointing facilities to support our growing subsea business and our customers project completion.

30 J.Ray NEWS www.jraymcdermott.com

FaBriCatioN oF SuBSEa HarDWarE Having established J. Rays proven welding processes and quad-joint fabrication capability for Tahitis subsea infrastructure, Chevron subsequently awarded J. Ray the fabrication of Tahitis eight PLETs and eight flowline jumpers. With fabrication resources already dedicated to the project and our welding criteria prequalified, we were able to handle the fabrication of the PLETS and jumpers very systematically, said Danos. The space afforded by J. Rays Morgan City fabrication facility allowed the team to fabricate the eight PLETs in parallel and perform factory acceptance and systems integration testing operations. Establishing four jumper fabrication sites, the jumpers will begin fabrication in May 2008.

oFFSHorE iN taHiti In August 2007, J. Rays DB50

mobilized to the Tahiti field to install four PLETs and four nine-inch production flowlines which were installed before the Spar hull. Additionally, J. Ray installed three large manifolds in up to 4,300 feet of water: an eight-slot production manifold weighing 250 tons, six-slot production manifold weighing 200 tons, and a discovery well tie-in manifold weighing 60-tons. The DB50 crew returned to the Tahiti field, in April 2008 to complete the subsea installation work. Two unique aspects remaining are the recovery and installation of the two export SCRs, a 20-inch and a 16-inch, that are on the seafloor, and the installation of the flowline SCRs to the Spar hull. The export SCR installation will be a challenge as DB50 will first have to recover them from under five mooring lines, said Danos. We plan to use an abandonment and recovery (A&R) winch to initially raise each SCR from the seafloor, then transfer rigging to move

sCr PuLL-in eQuiPmentlocation: installed on the top of the Spar hull to support the pull-in of the SCR flowlines to the hull. Equipment: 1,000 kip chain jack, mul-tiple routing sheaves, 1,700ft of 3 3/8 chain, chain locker to store the chain when not being used.

Once the crew has successfully welded each flowline SCR, the end will be low-ered into the water using an A&R winch and held in position. The DB50 must move close to the Spar hull to gather the end of the 3 3/4 chain and transfer it to the vessels chain receptacle. Once in place, the chain is locked in the recep-tacle while the loose end of the chain is attached to the pull-in rigging at the end of the SCR pull head. The complete rigging system is then lowered into the water using the J-Lay travel block and transferred to the A&R winch.

The load of the SCR is eventually trans-ferred from the A&R winch to the chain jack on the Spar hull, which begins to pull the chain and the SCR into the des-ignated pull tube below the Spar hull.

The base of each pull-tube is approxi-mately 588 feet below the water line, while the top of each tube is 35 feet above the water line. Once the pull head clears the top of the tube an SCR sup-port ring is installed on each SCR, which is then centered and placed on top of the pull-tube and a support ring is bolted up to the pull-tube.

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j-LAy AdvAntAgeMost conventional S-Lay pipelay vessels weld 40 or 80-foot long pipe joints and use multiple welding, non-destructive testing (NDT) and field joint-coating sta-tions. DB50s cost-effective 775-kips ca-pacity J-Lay system can handle 160-foot quad-joint pipe sections, with fully au-tomatic welding, NDT and field-joint coating operations in a single, fully en-closed station located at the base of the J-Lay tower.

J-Lay offers a great advantage over S-Lay with regards to fatigue. While the sag-bend stresses are similar between the two installation methods, J-Lay has lower stresses at the top of the pipe string in the order of 15-20 percent specified minimum yield stress (SMYS), while S-Lay typically sees 80-85 percent SMYS. This stress factor is important as the topside of the pipe sees higher cyclic loading, which determines the amount of fatigue damage induced during installation.

versAtiLe underWAter CAPABiLitiesDB50s high-capacity underwater lower-ing system allows J. Ray to install heavy manifolds in deep water. With its dy-namic positioning capability, the vessel can maneuver directly over the piles on which the production manifolds land.

The flexibility DB50 affords with its ca-pability to switch from installation of flowlines or mooring lines, to subsea and above-water facility installations uniquely benefit customers by improv-ing project schedules and reducing re-mobilization costs, which mitigates risks.

the load from the A&R winch to the DB50 derrick crane. Once out from under the mooring lines, the SCR will be brought to the DB50 for removal of subsea protective components and attachment of pull-in rigging. Well then pull the SCR into a receptacle located 500 feet below the surface using specialized pull-in equipment and rigging, positioned on the Spar hull to assist with pull-in operations.

tHE FuturE looKS DEEP Projects such as Tahiti involve highly sophisticated technologies and resources to ensure challenging deepwater hydrocarbon extraction is successful. This type of exploration is costly, risky and time consuming. High quality, reliable, safe performance on such projects is imperative. As the industry focuses on even deeper water extraction to meet the worlds increasing energy demands, solutions will become more concentrated

on and within the seafloor to allow optimal subsurface exploitation. J. Rays greater focus on its subsea business unit comes at a time when the industry is pushing further into new frontiers. Establishing a concentrated subseabusiness is relatively straight forward, explained Bruce Crager, J. Rays Vice President of Subsea. As the Tahiti project scope attests, we already have all the pieces vessels required to install flowlines, SCRs and other subsea hardware; high quality welding technology and fabrication facilities to construct quad joints, manifolds, PLETs, jumpers and more; and Mentors 20 years of proven subsea engineering capability. In addition, our project management, cost control and scheduling expertise, with J. Rays worldwide EPCI resources, enable our customers to realize their ultra-deep dreams, where certainty is imperative.