The Neptune Spar has a 72 foot diameter hull which is 705 feet long. A square centerwell, 32 feet by 32 feet, runs through the 275 foot long buoyant section and the 100 foot long tank at the keel, accommodating sixteen well slots. Freeboard is 55 feet and the hull supports an integrated deck assembly of two production decks with a clear workover deck on top. Though the design topside load for the spar is 6,600 short tons the dry lift weight was only 3,300 tons. The packaged workover rig with associated tubulars, hook load and consumables, together with produced well fluids and mooring line tensions, make up the balance of the design load. An active six point mooring keeps the spar on station, each leg consisting of a driven pile, a short length of chain, 2,400 feet of spiral strand wire rope and 1,050 feet of chain running through the fairlead, up through the chain jack and down into the chain locker. The spar hull was fabricated in two main pieces in Finland. These two pieces were then transported to a shipyard in the Gulf of Mexico. Using alignment fixtures fitted in the original fabrication yard and ballasting, the two main sections were joined afloat and welded together to form the complete hull. The one piece deck assembly was built in the Gulf of Mexico and consists of two main production decks with a workover deck, sized to handle a 1,000 hp packaged rig, on top. The decks are supported on the spar hull by four 5 foot diameter legs in the same way it would be carried on a conventional jacket. On the spar hull the matching leg sections are placed directly over the vertical bulkheads and the outer half of the legs continue some distance down the hull to help in load transfer. Each production deck is 136 feet by 101 feet while the workover deck is 131 feet by 81 feet. Facilities layout was traditional with the quarters, control rooms and power plant on one end and the gas compressors, glycol plant and flare boom on the other.
Neptune, Gulf of Mexico, Kerr McGee, America(North),