First Semisubmersible Rig Built On East Coast

The Ocean Scout, the first semisubmersible oil-well drilling rig to be constructed on the East Coast of the United States was towed from Bethlehem Steel's Fort McHenry shipyard on February 21 to a site below the Chesapeake Bay bridges, where final sections of the drilling derrick were erected.

The rig was then delivered to Ocean Drilling & Exploration Company of New Orleans, La.

It will be operated in the Gulf of Mexico by the Pennzoil Company.

Designed to be a mobile offshore drilling unit suitable for unrestricted ocean service, the Ocean Scout, with a lower hull length of 202 feet and width of 182 feet, was designed by Breit Engineering, Inc. of New Orleans.

The lower hull consists of two watertight structures 202 feet 'long, 32 feet wide and 28 feet deep, joined so that they are 150 feet apart on centers. Main members of the structure rising from the two sections of the lower hull are four 32-foot-diameter corner stability columns and four 10-foot-diameter interior columns, all interconnected by truss work.

Atop them is the upper deck which is 170 feet long, 150 feet in width and 14 feet deep.

The upper deck is watertight and contains the machinery spaces. Overall, the rig measures 108 feet from the bottom of the lower hull base line to the upper deck.

The operational draft will be 48 feet in depths of water from 80 to 600 feet. Towing is done with wire towing hawsers.

Provisions are made for carrying drilling water, fuel oil, liquid mud, cement and other drilling supplies. The living quarters, including staterooms, galley, mess, lounge, hospital, offices and passageways, are air-conditioned, Accommodations are designed for a crew of 59.

The most modern fire-fighting equipment, as well as all necessary navigation aids are provided.

About 7,000 tons of steel were used in constructing the rig, which will tower 257 feet aibove the water when under tow. Since clearance under the Chesapeake Bay bridges is only 186.5 feet, the upper portion of the derrick was erected at an anchorage just below the bay bridges.

The Ocean Scout will be moored by eight 30,000-pound anchors, each with 2,500 feet of 2j^-inch-diameter stud 'link anchor chain.

The unit is capable of drilling a hole in excess of 20,000 feet. Major items of drilling equipment include a 147-foot derrick, a 3,000- hp drawworks and two 1,300-hp mud pumps.

The main power plant for both drilling and vessel service includes diese'l engines with over 5,100-hp combined capability.

The sub-sea system includes a 20-inch blowout preventer stack with a 24-inch integral marine riser and a 13^-inch, 5,000-psi blowout preventer stack with a 16-inch integral marine riser. The marine riser is equipped with a hydraulic tensioning system. An underwater TV system is utilized to monitor and assist with sub-sea operations.

Two revolving cranes are situated aboard the drilling rig to provide loading and unloading capability