Marathon Utilizes Computer Graphics For First Computer-Designed Offshore Rig

The Gulfwind, the first completely computer- designed offshore jackup drilling rig, is under construction for Chiles Drilling Company of Houston, Texas, at Marathon LeTourneau Company's Brownsville, Texas, yard, Marathon announced from its Houston headquarters.

The Marathon-class 150-44-C cantilevertype jackup drilling rig was designed by a new Computer Graphics Section at Marathon Marine Engineering Company, division of Marathon Manufacturing Company. The new drafting-design system was formed as a state-of-the-art way to more efficiently and economically improve engineering drafting procedures, a Marathon spokesman said.

In addition to being computer-designed, the Gulfwind is being engineered and constructed by Marathon LeTourneau to incorporate every practical feature for efficient offshore drilling operations, plus comfortable living quarters for at least a 40-man crew.

To be fully equipped for exploratory or development drilling up to 15,000-foot depths, the Gulfwind has an unusual cantilever design permitting drilling multiple wells without moving the rig.

In order to design the Gulfwind by computer, many of Marathon's engineering drafters have been retrained to extend their knowledge into the sophisticated computer-aided graphics area to become computer drafting specialists.

Five new computer graphics modules with fully trained drafters-operators can draft a rig design at least twice as fast as the tedious manual drafting procedure, it was said.

The computer design module works like a typewriter attached to a video screen and is used to create a visual design or layout of a rig. These units can project graphic illustrations such as structural shapes, connection details, welding symbols, and other engineering symbols onto the screen where required on the rig layout, and as many times as needed.

Complex engineering drawings are thus possible by programming the system to do extensive mathematical calculations that can be interacted with the graphics system, according to the spokesman.

The Chiles's Gulfwind rig order, described a "Hull 152" at Marathon, started on its way in Marathon Marine Engineering's General Arrangements Group, after receiving a set of rig specifications supplied by Chiles Drilling Company, Here, the general rig layout and owner-specified modifications are incorporated into the design via one of the computer design modules.

The general rig layout includes an overall view of the rig, general layout of machinery and main decks, crew quarters, and interbottom tanks. The layout is dispersed to four other computer-graphics drafting disciplines, a Structural Group, an Electrical Group, a Mechanical Group, and Piping Group, each with its own computer-graphics module.

Concentrating on the hull design of the rig, the Structural Group specifies the size and type of steel to be used in rig construction.

Some 30 computer-aided drawings are required to show plating and framing for the bottom, machinery and main decks, spud wells for the jackup legs, and bulkheads and structural frames.

The Electrical Group executes about 40 computer-graphics drawings for the lighting, telephone and general alarm systems for the rig. They also lay out drawings for the wiring systems for any specified cranes, winches, and skidders for the drill floor.

Approximately 15-20 computer-graphics drawings are required from the Mechanical Group, which develops the drawings for the heavy structural skid rails, pipe racks, gear boxes, generators, water towers, crane columns, and spud legs.

All industrial piping computer-graphics drawings for the drilling function of the rig is provided by the Piping Group, as well as all standard rig piping such as bilge, ballast, pre-load, potable water, and sanitary and fire systems, all requiring some 30 drawings.

After a rig design has been completed and approved, finished drawings are made on a Computer Plotter and stored for recall at any time in a Central Processing Unit. Finished (approved) drawings are made on the Computer Plotter. A Computer Digitizer is also used to trace existing drawings, which can be stored in the Central Processing Unit for recall onto the Plotter for a finished drawing.

The Chiles's Gulfwind has been designed with a 153.5-foot by 160-foot hull to provide generous deck space for efficient drilling operations.

The rig's 248-foot-long legs can be recessed into the hull for towing into waters as shallow as 15 feet. The rig elevating system will extend the legs at the rate of 90 feet per hour to position the rig on station in waters up to 150 feet deep.

According to Marathon engineers, the Gulfwind is designed to be ideally adapted for relatively shallow-water drilling operations.

Though specially designed by Marathon for the Gulf of Mexico, it will perform just as efficiently off the West Coast of Africa, in the Caribbean or Indonesian waters, or wherever similar environments are found, it was said.

Marathon LeTourneau Company is a division of Marathon Manufacturing Company, Houston. In addition to being the leading manufacturer of mobile offshore jackup drilling rigs, the parent company is a multiproduct company manufacturing materials handling equipment, steel products, steel buildings, white oils, batteries, consumer goods, and providing civil engineering and construction services. It is a subsidiary of The Penn Central Corporation.

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