Glomar Explorer Converted for Deep-Water Drilling

The well-known salvage ship Glomar Explorer arrived Cascade General in February after 20 years in lay-up. It departed in June well on it's way toward its new mission as a state-of-the-art, deepwater drill ship after 135 days of round-the-clock work. This remarkably fast conversion was completed 15 days ahead of schedule and included a virtual doubling of specified work from the original contract terms.

Some 5,000,000 lbs (2,267,950 kg) of steel were used in the primary modifications. The 619-foot (188.67 m) ship was lifted and blocked at the bilges with a 12-foot (3.65 m) clearance. In a carefully orchestrated sequence, the retractable gates covering the Glomar Explorer's 200-foot (96.96 m), "moon pool" were cut away, lowered and removed. Prefabricated, bottom modules were floated in, flooded and inserted into place, leaving a 74' x 42' ft (22.5 x 12.8 m) drilling pool.

The ship was lifted again on standard 6-foot (1.8 m) blocking and the new bottom welded into place. Two bulkheads were erected above the new pool, the aft one carrying a 25-ton (22.67 m ton) rack to support the 175-ton (158.7 m ton), blow-out preventer. The new fore hold will contain stacks of riser pipe and related stores. To one side is a new moon pool, 16' X 19' (4.87 x 5.79 m), specifically for Remote Operated Vehicle (ROV) deployment. The ROV will have the ability to inspect the seabed at great depths and will have its own service facilities and stowage area on deck.

The aft hold required extensive demolition and re-construction to support the loads imposed by ten 40' x 15' (12.19 x 4.57 m) mud tanks, five, 7,500 PSI mud pumps and a new electrical generator room housing four, EMD 645 16-cylinder AC generators, each weighing 40 tons (36.2 m tons). The electrical output is generated at 4,160 volts AC, stepped down and rectified to 440 DC via two, new (SCR) control rooms. A powerful, 1,140 KW, emergency generator was installed aft of the bridge and also demanded extensive structural modification.

The ship's diesel-electric propulsion system - five Nordberg 16-cylinder AC generators turning six, 2,200 HP DC shaft motors - was overhauled and rebuilt where necessary. The twin propellers and shafts and all five 2,000 HP, shaft-driven thrusters were returned to top condition while the exterior received a five-year coating system before the ship was refloated.

The provision of ventilation to these numerous spaces necessitated retrofitting an entire system from the new deck down. Besides vent shafts, the deck plan called for 25 hatches, scuttles and davits for four Schat-Harding, 60- and 80-person, self-righting lifeboats. Access to the helicopter deck has been strengthened to carry a forklift and under-deck reinforcement has been added to support four Seatrax cranes, with boom lengths of 90-110 feet (27.43-33.52 m).

"The GLOMAR conversion has been the largest, most complex project in the history of this yard," said Cascade General Executive Vice President Andrew Rowe. "It has enabled us to demonstrate the full potential of Portland Shipyard and Cascade General as major players in the US conversion market."

Integral to its new role of deepwater, oil prospecting, the Glomar Explorer will need the ability to hold position of +10 feet (+3.04 m) over a drill site up to 7,500 feet (2,286 m) deep. This necessitated additional thrusting capability in the form of four new 3,000 HP azimuthing units operating in 50' X 12.5' (15.24 x 3.81 m) vertical tubes. These electric thrusters can be raised and inspected at deck level via a vertical rail system, built to machine-level tolerances.

The total power of the nine thrusters is 22,000 HP, greater than the ship's main propellers. All eleven screws will be connected to the vessel's new, dynamic-positioning system. Six 18-inch (45.72 cm) tubes projecting from the main deck to the bottom have been installed to carry the hydrophone array. The bridge has been completely re-designed to meet these precise, navigational needs.

"In many ways, the complex demands of this job are greater than with new construction," observed Alan Jones, Cascade General Project Manager and a 25-year veteran with the yard. "The Glomar Explorer contract has made full use of all our assets: the dry docks and cranes, workshops and workforce. We've also had great support from local specialists/sub-contractors."

"We have overcome numerous challenges, from containing the lead paint removed from the houses to removing the original, 150-ton (136 m ton), heavy-lift girders over the pool," added Ship Superintendent Jim Mattix. "Our goal has been to upgrade the existing systems to full ABS standards to match all the new equipment we've added."

After load testing of the engines and sea trials, the Glomar Explorer will be delivered under its own power to the Gulf Coast via Cape Horn, where it will be fitted out and commence work under a five-year, exploration contract. According to Jeff Shepard, Global Marine Construction Manager, "The work accomplished in Portland has been a critical milestone in the process of creating a state-of-the-art, deep-water drill ship. We are confident this ship will be on the leading edge of exploration technology and the equal of any vessel afloat. Cascade General has the unique features, manpower and expertise to perform this kind of conversion and has been responsive to the owner's needs."

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Glomar Explorer
(Project Profile)

Cascade General operates Portland Shipyard, the largest and most complete ship repair and industrial facility on the West Coast of the United States. We provide full-service repairs and conversions for tankers, cruise ships, bulk carriers, container ships, government vessels, tugs, barges and workboats. Cascade General's Portland facility includes a 60-acre (24.2 ha) yard, 550,000 square feet (51,096 square meters) of craft shops, more than 7,600 ft. (2,326 meters) of full-service repair berths, and two floating dry docks.