In recent years, the SPAR concept has emerged as a viable option for deepwater development. The SPAR is a floating cylinder that supports a deck and is connected to the seafloor by mooring lines. It may or may not have a change in diameter (neck) below the water surface. The SPAR enjoys some desired motion characteristics, such as low heave response due to its deep draft, insensitivity to water depth, and relative insensitivity to deck loads. SPARs can support rigid risers, steel catenary risers and well surface trees, which have made SPARs even more desirable in deepwater.

INTEC, as a leader in deepwater floating systems development projects, has the experience and capabilities required to perform SPAR projects. The INTEC Floating Systems group has accomplished the following SPAR and TLP projects.

Leviathan Gas Pipeline Company SPAR Sensitivity Study
INTEC conducted a sensitivity study to determine the size and associated CAPEX of SPAR type systems for three different topside weights with varying quantities of risers and flowlines. The study also included SPAR sensitivity to changes in water depths that ranged from 914 m (3,000 ft) to 1,524 m (5,000 ft). The selected SPAR/concepts utilized open centerwells to support top tensioned surface production risers and trees and provides workover capabilities. Cost estimates and schedules for the design and construction of the SPAR were developed.

This study was subsequently followed by the Leviathan Sunday Silence Field Development. The Sunday Silence Field is located in Ewing Bank Blocks 958, 959, 1002 and 1003 offshore Louisiana in the Gulf of Mexico in 1,490 ft water depth. INTEC responsibilities included the preparation of the FEED, Invitation to Bid package, contractor scope of work, production riser design and overall system design basis. The following TLP/SPAR type designs were considered for development of the field and competitive bids were obtained from four contractors:

• Atlantia Offshore Super SeaStar Mini-TLP
• MODEC International Moses Mini-TLP
• Kvaerner Deep Draft Floater
• Spars International Truss Type SPAR

• Overall Project Management
• Invitation to Bid Preparation
• Metocean Data Coordination
• Geophysical Data Assessment
• Production Riser Design Criteria
• Global Performance Design Criteria
• Pro-Forma Contract Agreement
• Bid Clarification Activities
• Contract Negotiations
• Detailed Engineering Design Supervision
• Geophysical/Geotechnical Survey Management
• Steel Catenary Riser (SCR) Detailed Design
• QA/QC/Weight Monitoring
• Project Control Coordination
• Fabrication Supervision

A contract was awarded to MODEC International for the fabrication of the Moses TLP hull, tendons and production risers. Fabrication began at the AMFELS Fabrication Yard in Brownsville, Texas in September 1999. This contract was cancelled late 1999 when the project was suspended due to a change in the field operatorship.

Vanco Energy Company Manta Field SPAR, Offshore Gabon
INTEC performed a study to determine the size and CAPEX requirements for a Drilling and Production SPAR in a water depth of 1,860 meters (6,100 ft) with one million barrels of oil storage. The study included CAPEX and OPEX comparisons for three different storage possibilities:

• SPAR with a storage capacity of 100,000 barrels and dynamically positioned (DP) FSO serviced by conventional shuttle tankers.
• SPAR with one million barrels of storage and conventional shuttle tankers.
• SPAR with two million barrels of segregated storage and conventional shuttle tankers.

Reading and Bates Development Company SPAR Design
INTEC developed a conceptual cost estimate, concept design and development schedule for a Production SPAR for a water depth of 1,160 meters (3,800 ft) in the Gulf of Mexico. The SPAR was a site-specific design that can be adapted to meet different field requirements. The objective was to complete sufficient engineering and drawings to issue Invitations To Tender to qualified shipyards and contractors to obtain firm quotations.

The initial engineering phase of the project was primarily focused on conceptual engineering. Model testing and detailed engineering would be accomplished during the next phase of the project. One concept was based on a SPAR having a square cross section moored to the seafloor by 12 catenary mooring lines, three from each corner.

Union Pacific Resources Mini-Floater Study for Mississippi Canyon Developments
INTEC conducted a study to determine the size and CAPEX of a minimum facilities SPAR for the Mississippi Canyon area in the Gulf of Mexico for a water depth of 930 meters (3,050 ft). The Mini-Floater was sized to support topside weight of 2,000 tons. The mini-floater selection was optimized based on several factors such as keel offset, maximum surge excursions and mooring system requirements. The mini-floater CAPEX was developed for several types of mooring lines and anchoring systems after determining their applicability to the Mississippi Canyon area. Design and construction schedules were also prepared.

Confidential Minimum Facilities SPAR Study
INTEC conducted a study to determine the size and CAPEX of a minimum facilities SPAR for the Gulf of Mexico in a water depth of 914 meters (3,000 ft). The minimum facilities SPAR would be unmanned and would not have oil storage, drilling or workover capabilities. The SPAR was connected to the seabed by taut synthetic mooring lines. Two topside weight options with varying number of steel catenary export and flowline risers (SCRs) were used to select one SPAR design concept that would satisfy both topside weight options. Cost comparisons for varying water depths, anchors and mooring line components were developed.