State-of-the-Art Drill Ship Conversion

Aft moon pool double-bottom module being floated into position under the ship while semi-submerged on Dry Dock 4

Glomar Explorer

2,250 tons (2,041 tonnes) of steel installed

Extensive structural modifications

Major machinery installations

Ship delivered ahead of schedule

Fore/aft double-bottom modules inside the ship's moon pool during initial fit-up. Drill well in center, ROV moon pool at bottom right

Four large mud pumps were installed under deck at center

Cascade General completed the conversion of the Glomar Explorer, a 619-foot (188 m) vessel, into a deepwater oil drilling ship. This was one of the most complex projects ever undertaken in the history of the company, involving fabrication of more than 4.5 million pounds (2,041 tonnes) of steel and reactivating virtually every system on the vessel.

In a carefully orchestrated sequence, the 619-foot (188 m) ship was blocked and lifted, and retractable gates covering the 200-foot (60.9 m) "moon pool" were cut away, lowered and removed. Prefabricated bottom modules were floated in and inserted, leaving a 74- x 42-foot (22.5 x 12.8 m) drilling pool.

The ship was lifted again, and the new bottom welded into place. Two bulkheads were erected above the new pool, creating fore and aft holds. To port is a separate 16- x 19-foot (4.8 x 5.7 m) moon pool for Remote Operated Vehicle (ROV) deployment. The aft hold required extensive demolition and reconstruction to support loads imposed by ten 40- x 15-foot (12.1 x 4.5 m) mud tanks, five 7,500 PSI mud pumps and a new electrical generation room. Four EMD 645 16-cylinder AC generators, each weighing 40 tons (36 tonnes), were installed. Twenty-four (24) new digital SCRs were installed in forward and aft rooms. A powerful, 1,140 KW emergency generator installed aft of the bridge also demanded extensive structural modification.

The ship's diesel-electric propulsion system - five Nordberg 16-cylinder, 4,160 volt AC generators turning six 2,200 HPO DC shaft motors - was overhauled and rebuilt. The twin propellers and shafts and all five 2,000 HP shaft-driven thrusters were returned to top condition.

Integral to its new role of deep-water oil prospecting, the Glomar Explorer needed the ability to hold positions of +10 feet (+3.0 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-foot (15.2 x 3.8 m) vertical tubes, which were installed to a tolerance of 1/4" (6 mm) over the 52-foot (15.8 m) length.

Glomar Explorer after hull structure modifications at Cascade General