Floating dry dock and wheel-on-rail system expedites jack up repairs

Dean E. Gaddy
Drilling Editor

A unique wheel-on-rail system and floating dry dock expedited leg removal and repair work on a Gulf of Mexico jack up.

Sundowner Offshore Services Inc. contracted Ingalls Shipbuilding of Pascagoula, Miss., to replace the jacking gears and racks for the Dolphin 110 (Fig. 1 [24,250 bytes]).

To transfer the jack up onto dry land, the floating dry dock was centered over a deep-water pit located to the right of Fig. 1. The dry dock was then submerged by filling ballast chambers in its wingwalls and wall sections. The jack up was then towed inside the dry dock, the dry dock unballasted, and the jack up raised above water level with the rig's mat sitting on top of a parallel, shoreward-oriented rail system of strongback rail cars. Fig. 2 [41,099 bytes] shows a top view of the jack up on the dry dock.

The dry dock was repositioned against the shore side of the construction area, and the three wingwalls were removed (one is missing in Fig. 1). The jack up was then wheeled ashore atop the strongback rail cars. Fig. 3 [35,207 bytes] shows a side view of the rig mat set on the strongback rail cars.

Once onshore, the four 190-ft legs were cut at the 60-ft level. The remaining 130-ft sections were then laid down with cranes and taken into the covered slab-area work bays where repair work would be unhampered by weather conditions.

According to Sundowner's project manager, Randy Murrell, horizontal leg repair work is superior to vertical. He said vertical alignment would have been more difficult, and repair work would have taken longer.

The Dolphin 110 arrived at Ingalls' shipyard May 5, 1997, and returned to Gulf of Mexico duty Aug. 20, 1997. The jack up can operate in water depths of 11-115 ft and can drill to depths of 14,000 ft.

According to Ingalls' manufacturing vice-president, Benny Lassitter, Ingalls' employees are pleased to once again be working in the offshore oil industry. During the 1980s, the shipyard built 17 jack up and submersible rigs, but during the 1990s, no major oil field construction or repair work occurred. Preparing for future construction and repair activity, Ingalls is planning a $25-million project which includes a 160-ft, detachable dry dock expansion that will be able to launch and recover a variety of offshore rigs.