Page 11: of Maritime Reporter Magazine (February 15, 1973)

EKOFISK CRUDE OIL STORAGE TANK

ONE-MILLION BARRELS 1. Water depth at Ekofisk location: 230 ft. 2. Tank structure will rest on seabed. (Weight of the tank will cause it to pene- trate the firm sand bottom 1.0' to 1.5') 3. Perforated outer wall (breakwater) will extend above sea level 39'~4". 4. Inner wall (tank) will extend above sea level 65'-8". 5. Total tank height: 295'-8". 6. When completed in Stavanger Fjord and ready for tow to site, the tank will have 197' draft. 7. There are 8,000 circular holes in the outer breakwater wall. Diameter of the holes range from 2'-8" in the lower portion of the wall to 3'-7" midway up the wall to 4'-3" in the upper portions of the wall. 8. Horizontal dimension of the structure is 302' outside to outside of break- water wall. 9. The breakwater wall is 6'-6'' thick for the upper 105' of its height, and 4'-5" thick for the lower 164' of its height. 10. The horizontal dimension of the inner tank is 175' outside to outside of walls.

I 1. Thickness of the inner tank walls is 20". 12. Approximately 100,000 cubic yards of concrete are required for the com- pleted tank.

Unique Storage Tank— (Continued from page 11) weight moved, draft below the wa- terline, .beam of vessel, and the sheer volume of a manufactured item in controlled sailing will be eclipsed.

The completed project, which will include a huge platform over the entire tank for helicopters, stor- age space and other elements for a man-made island, will encompass between 480,000 and 500,000 tons of construction materials. With a horizontal dimension of 302 feet, which includes a specially-designed outer breakwater and the nine hold- ing tanks inside, the concrete tank under tow will far exceed the larg- est oceangoing tankers now built or contemplated in width of beam.

In its short ocean voyage to Eko- fisk from Stavanger fjord, it will also set an unheard of draft record of 197 feet. Truly, the only floating objects that are larger, wider, and with greater draft depths are ice- bergs.

To put the tank "vessel" into proper perspective with other man- made sailing objects—oil tankers—• the facility to be moved to Ekofisk is by far the largest in all of its dimensions with the exception of tank capacity. The latter total, how- ever, represents a calculated busi- ness estimate of oil storage needed to maintain a smooth and steady flow of petroleum from the offshore site to terminals on land to offset possible production interference from ocean storms.

As a comparison of the concrete tank with seagoing tanker giants, the biggest ship now afloat is a 477,000 deadweight ton tanker be- ing readied for service in Japan.

The ship—the Globtik Tokyo—is one of three of similar size being built in Japan. Contracts, mean- while, have been awarded for con- struction of even larger oil tankers —530,000 dwt—for the Shell Oil

Corp.

The Globtik Tokyo is slated to go into operation very shortly.

When it begins operating it will be the all-time giant carrier, topping the current record holding ship in terms of size by some 110,000 tons of cargo capacity. However, even fully laden with oil, which it moves regularly from the Persian Gulf to

Japan, the present record size ship would not equal the floated weight of the Ekofisk tank. Moreover, the beam of the biggest tankers at some 240 feet and their draft of between 90 and 100 feet fully loaded are on- ly about half that of the concrete tank when it makes its memorable voyage this year.

Referred to with affection as "The

Thing" by the American, Norwegi- an, French and other workers in- volved in the construction, the tank will be installed in Ekofisk, where exploration for oil is continuing.

Phillips reports that the oil con- sortium is now completing four ex- ploratory wells and plans to begin work soon on three new drilling platforms. Sitting on the sea bot- tom and connected to the produc- tion pipelines in the nearby wells, the concrete tank will permit un- interrupted oil flow even during typical violent, stormy North Sea weather conditions, when tankers are unable to dock at the terminal for loading.

Designed by a French company, the tank uses a patented energy- absorbing breakwater and an inner section to hold the crude oil. The breakwater, a perforated wall mea- suring 302 feet in diameter, is link- ed to the inner tanks by a series of perforated walls, all of which are made rigid and secure by high strength steel cables that encircle the tank in all directions.

The perforations in the breakwa- ter are designed to help absorb en- ergy against the structure by allow- ing sea water to flow into the wa- ter-filled space between the inner and outer walls.

Two Norwegian engineering firms are building the structure at a point in Stavanger fjord where the water depth is greater than that at the site at Ekofisk. However, this is not where it all began. Initi- ally a sheet pile cofferdam was built across a small inlet to form a dry-dock for construction of the tank bottom.

When the self-floating 20-foot thick concrete cell that forms the tank bottom was completed, it was moved into deeper water where the vertical walls are being con- structed by the slip-form method.

Perforations in the outer wall are formed by inserting precast units into the wall as slip forming pro- ceeds. As the tank grows, it is moved farther out of the inlet into deeper water, so that only the up- permost section is above water.

The oil storage section will be divided into nine compartments, for maximum structural strength.

Inner walls and partitions are be- ing formed from 20-inch thick re- inforced concrete. The outer walls are six feet thick from the top down through the surf zone, and taper down to four and a half feet at the bottom.

The top of the tank will -be deck- ed to provide 30,000 square feet of usable platform space. Eventually a 750-foot bridge will connect the deck to a field terminal complex to be built nearby.

When completed, the million barrel tank will sail under tow to its final destination. Towing time is estimated at five days. Once the tank is on site and anchored in position, sea water pumps will flood the storage compartments and cause the tank to submerge to its final position on the seabed. The lowering operation is calculated to take 24 hours. However, the pro- cess is reversible at any time in the event of an unexpected storm.

With the Norwegian government insisting on anti-pollution stand- ards in every possible aspect of the

North Sea exploration program, the tank will include a variety of sensors and pollution control de- vices and pumps.

Phillips reports that special con- sideration has been given to pollu- tion control and several safety fea- tures have been included in the storage tank design to protect against harmful spills. As an ex- ample, a water tank is being built into the roof of the tank to pro- vide a means of oil/water separa- tion and to assure that no oil will be discharged into the surrounding sea.

Additionally, the oil storage sec- tion of the tank is completely iso- lated from the sea, and, in the event of a ship-storage tank collision, the thick outer breakwater affords maximum protection for the storage compartments.

However, beyond even such eventualities the construction is geared to safety and strength. Built in the form of a network of thou- sands of multi-strand steel cables tensioned by tremendous pressure, the tank is covered by the thick concrete walls. In fact it is a sin- gle, unitized structure, whose cir- cular form is capable of offering the greatest possible resistence to outside forces that may come against it.

Once in the water, it will always function with either oil or sea wa- ter within its compartments to pro- vide equal weight pressure on the walls, according to a structural en- gineer at the site.

Donald J. Main

Joins ConAgra's

Ocean Shipping Staff

Donald J. Main

Donald J. Main, former planning and development coordinator for

Ingram Ocean Systems, has joined

ConAgra, diversified international foods company headquartered in

Omaha, Neb. He will work in the company's ocean shipping program and report t'o the office of the presi- dent.

Mr. Main, whose experience in- cludes both naval and mercantile vessel service, also served as a ma- rine engineer with Shell Oil. Prior to that, he was a test engineer in the naval nuclear department of the

New York Shipbuilding Corp.

While in the U.S. Navy, Mr. Main served as a lieutenant aboard die- sel-electric submarines.

He earned a bachelor of science degree in 1959 from the Maine Mari- time Academy. He also received special training in marine capital expenditure and operating manage- ment in London.

ConAgra, with 66 plants in 20 states, also has extensive opera- tions in Puerto Rico, Spain and

Portugal.

Drew Chemical's

Ameroid Marine Div.

Names John P. Kay

John P. Kay

John P. Kay has been appointed

Regional Manager for the Ameroid

Marine Division of Drew Chemical

Corporation in the United States.

Drew Chemical is a subsidiary of

United States Filter Corporation.

A graduate of the United States

Merchant Marine Academy at

Kings Point, Long Island, N.Y.,

Mr. Kay joined Drew in 1964, and has served as industrial national accounts manager, and as assistant marine sales manager.

He will be headquartered at Drew

Chemical's New York City loca- tion at 522 Fifth Avenue.

February 15, 1973 13