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ABS Speeds Truss Spar Projects in Gulf of Mexico
| MEDUSA Truss Spar will be ABS-classed as an X
A1 Floating Offshore Installation, and will be located on Mississippi Canyon Block 582 in 2,223 feet of water. |
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| ABS is classing and certifying several other deepwater truss spar projects now under way. Projects in addition to Medusa and Devils Tower include Kerr-McGee’s Boomvang, Nansen and Gunnison spars, and BP’s Horn Mountain and Holstein spars. |
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"Our capabilities with both caisson and truss spar technology help our customers over regulatory hurdles. With our exclusive delegations of authority, we can significantly shorten turn-around time with the Coast Guard on ABS-classed installations."
Lynnda Pekel, ABS Project Manager |
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russ spar installations will provide vital avenues for deepwater GOM developments. Applying |
its deepwater expertise, ABS is presently providing classification services while facilitating fast-track fabrication and installation schedules for Murphy Oil’s Medusa truss spar and for the Dominion/Williams Devils Tower truss spar, currently the world's deepest dry tree platform in progress.
As with all floating production systems operating in the Gulf of Mexico, these two projects must comply with federal regulatory codes in order to receive a Certificate of Inspection (COI) from the United States Coast Guard (USCG) and a permit to operate from the Minerals Management Service (MMS), says Lynnda Pekel, ABS project manager for both the Medusa and the Devils Tower truss spars.
"The rapid and efficient interface that ABS maintains with the Coast Guard, the MMS, oil and gas companies and various contractors and vendors significantly accelerates the regulatory compliance of these Gulf of Mexico deepwater applications," says Pekel.
Tim Parker, Senior Vice President and General Manager, Offshore, for Dominion Exploration & Production, Inc., echoes this point while underscoring ABS’ industry leadership.
"ABS is the dominant leader in offshore classification and provides all the necessary services in one package. Dominion can count on ABS to do the required classification of the vessel; to be the USCG delegated reviewer of the design, fabrication and installation; and to serve as the certified verification agent for the MMS," says Parker.
About Truss Spars
Truss spars—similar to caisson or classic spars in their operational profile—are intended to offer some design improvements. The truss spar is primarily characterized by its space frame of tubular members, which provides the structural linkage between hard tank (flotation tank) and keel tank as well as support to the heave plates. The heave plates provide added mass and damping to further reduce heave motions and to improve stability. This arrangement is intended to save steel, allowing additional deck load, and providing required motion response performance.
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In general, spar systems are particularly suited to deepwater Gulf of Mexico applications by providing operators with increased flexibility in terms of water depth capability, extending traditional floating technology to 10,000 feet of water.
"Our capabilities with both caisson and truss spar technology help our customers over regulatory hurdles. With our exclusive delegations of authority, we can significantly shorten turn-around time with the Coast Guard on ABS-classed installations," says Pekel.
The ABS/USCG delegations allow a large part of the design to be reviewed and approved by ABS on behalf of the USCG. Further, ABS is authorized to carry out field inspections on behalf of the USCG under these authorizations. More recently, ABS delegation was extended to stability-related requirements for the USCG, including issuance of the USCG stability letter, greatly streamlining the entire process.
Quick Responses to Client Class & Regulatory Questions
ABS also assists clients with preliminary planning and advice early in the project, including pre-sanction FEED phases, through onsite meetings and review of design bases. ABS provides quick written responses to clients’ important class and/or regulatory questions through a query system and consults with clients regarding regulatory and class citations. ABS outlines the technical drawings and calculations, which are required for classification, coordinates all equipment vendors relative to ABS class and regulatory requirements and conducts meetings as needed.
"This preliminary review identifies potential problems and weeds out a lot of issues regarding hydrocarbon, safety and marine-related systems to streamline and speed the process. We are in constant contact with all players and respond rapidly to all queries," says Pekel.
She adds that the success of fast-track projects stems from designs that are as detailed and mature as possible, prior to cutting steel. Importantly, early communication and decisions regarding classification and regulatory issues support this fast-track effort and can lead to timely installations and production start-ups.
To address stringent regulatory issues, ABS design approval proceeds through a technical review of hull and topside structures, foundations/moorings, marine, utility and safety systems, global performance, overall stability, and, if included in the scope of classification by the owner, the hydrocarbon production facilities. ABS, working on behalf of the USCG throughout all these phases, also surveys the hull, topsides and piles/moorings during the fabrication, installation and commissioning stages.
Coordinating Additional USCG Requirements
Additional USCG requirements, which ABS can coordinate, call for certifiable marine-related components, including systems for power generation, fuel, potable water, crew habitability and general safety. Specific safety plans, fire-fighting systems and operating manuals are reserved for USCG final approval.
As an ABS service apart from USCG requirements, ABS can perform specific design review methodology, which includes time domain analysis and simulation of extreme response distributions. Motion/mooring analysis employs hydrodynamic and time domain software.
ABS has extensive experience with spars in the Gulf, including classification of the Kerr-McGee Neptune spar hull and topsides in 1996, which also included delegations by USCG as well as MMS Certified Verification Agent (CVA) work. More recently, ABS classed, performed approvals on behalf of USCG and carried out CVA activities for ExxonMobil’s Hoover/Diana DDCV.
ABS is classing and certifying several other deepwater truss spar projects now under way. Projects in addition to Medusa and Devils Tower include Kerr-McGee’s Boomvang, Nansen and Gunnison spars, and BP’s Horn Mountain and Holstein spars.
Medusa & Devils Tower
J. Ray McDermott, a subsidiary of McDermott International, is the EPCI—engineering, procurement, construction and installation—contractor for both the "Medusa" and "Devils Tower" spars.
ABS-classed as an X
A1 Floating Offshore Installation, the Medusa truss spar will be located on Mississippi Canyon Block 582 in 2,223 feet of water. Murphy Oil is the operator with a 60 percent operating interest; other interest holders include Agip Petroleum and Callon Petroleum. The sixth truss spar to be installed in the Gulf, Medusa will be of similar size to the Boomvang and Nansen projects.
SparTEC, a wholly owned subsidiary of J. Ray McDermott, is the general contractor for Medusa engineering, procurement, installation and construction (EPCI), and Mentor Subsea Technology, another McDermott subsidiary, is handling the design and procurement of the production risers. Upon completion, the facility will have capacities of 40,000 barrels of oil per day and 110 million cubic feet per day of gas. First oil is scheduled for November 2002.
Meeting the challenges of deepwater design and installation, the Devils Tower spar—lighter in weight than the Medusa spar—will employ different riser material because of its increased water depth location. Destined for Mississippi Canyon Block 773 in 5,610 feet of water, the Devils Tower spar is operating on a very fast track, with the project scheduled to complete in 18 months. First oil is anticipated for mid-2003.
"ABS experience with floating production units and pipeline and riser systems is vital to the efficient and timely completion of all phases of these projects," says Pekel.
ABS has classed all 14 of the classed floating production units now operating or under construction in the Gulf, with certification involvement with all 28 such systems in the Gulf. Including the Medusa and Devils Tower spar projects, ABS has performed classification or certification services for 82 floating production units worldwide.
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