Marathon-Built Rowan Gorilla I Now Drilling Offshore Nova Scotia

The Rowan Gorilla I, the first Gorilla Class jackup rig built by Marathon LeTourneau's Marine Division in Vicksburg, Miss., is now on location 268 miles east of Halifax, Nova Scotia, near Sable Island, an area where extreme cold is part of the working environment.

The rig's winterizing features are said to be working quite well.

Owned by the Rowan Companies, Inc. of Houston, the new rig is on its first drilling assignment.

It is working in 207 feet of water drilling a rank wildcat for a group of Canada-based companies including Bow Valley Industries Ltd., Husky Oil Operations Ltd., and ATS Explorations.

The rig left New Orleans in December 1983 and made its first tow, 2,300 miles to Halifax, in 17 days. The Gorilla's hull has been redesigned, and proved to tow very efficiently. The largest electromechanical jackup ever designed and built by Marathon, a Gorilla Class rig can operate year-round in remote offshore areas with hostile operating conditions.

Gorilla Class units have the unique Marithon LeTourneau Slotilever"'.

This means the rig can not only cantilever the derrick out beyond the stern but can also drill during design storm conditions with the drilling package fully retracted into the slot. Gorilla rigs are also capable of ocean tows and field moves with all 504 feet of leg in place; this greatly adds to the rig's mobility. The size of the Gorilla rig—the main deck covers nearly one acre—allows for storage of large quantities of drilling consumables. These rigs can continue to work even if resupply is temporarily interrupted.

Classed +A1 by the American Bureau of Shipping and constructed in accordance with U.S.

coast Guard Mobile Offshore Drilling Unit Regulations, the rig also meets or exceeds the requirements of the Canadian Coast Guard, the U.K. Department of Energy, and the Netherlands Department of Mines. The Gorilla has been designed by Marathon to survive up to 90-foot waves and 82-knot winds when drilling in 328 feet of water.

The Rowan Gorilla I has power to spare, with seven Caterpillar D399 diesel engines with a total output of 11,080 at 1,225 rpm.

These drive seven generators that produce a total of 7,210 kw. Power for the rig's propulsion assist system is provided by eight electric motors with a total output of 6,800 hp, connected through gearboxes to two 112-inch propellers in Kort nozzles. These motors are mounted on the machinery deck on either side of the drilling slot. When using a 10,000-bhp tug, the assist thrusters will increase the towing speed by about two knots.

Living accommodations are provided on the Rowan Gorilla I for 80 persons. Other features include a six-bed hospital, dual galleys, dining room, and recreation facilities.

The rig's survival system consists of two 50-person and two 34- person Whittaker enclosed capsules, approved by the U.S. Coast Guard and fitted with communications systems. An octagonal helipad cantilevered out over the bow has a diameter of 83 feet and is elevated approximately 75 feet above normal draft for sea tow purposes.

Two other Gorilla Class rigs are currently under construction, one at Marathon's Singapore yard for late 1984 delivery and one at the Vicksburg yard for delivery in 1985.

Maritime Reporter Magazine, page 22,  Apr 1984

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