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Volume 11, Number 6June/July 1960

In This Issue

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Oil Field Under The Sea

Deep under the Persian Gulf floor, six limestone reservoirs of oil nestle into each other like upside down cereal bowls.

The water taxi sliced a furrow through the emerald green of the Persian Gulf and splashed the white spume against the cockpit windows. As the Saudi Arab helmsman steered ENE by the compass, he worked his windshield wiper to brush away the caked salt. Although he was in contact by radiotelephone with the rock-filled Manifa pier astern and with the unseen floating island ahead, he had to thread his way through a maze of coral reefs lying athwart his 14-mile course. One by one, he picked up the navigation buoys and lights and gave them a wide berth.

"Don't you write anything nasty about those coral reefs," Sam Zimmerman, the burly chief geophysicist of the Arabian American Oil Company, was saying, as he shielded his camera lens from a splash of spray. "Maybe they are a hazard to navigation. But they came in mighty handy at one time. They made a nice solid platform, jutting out of the sand and mud on the floor of the Gulf. On just about every one of them, we set up a light rig and bored a shallow hole. We wanted to see what sort of rock structure lay underneath, to see if there was a good enough chance to warrant the costly gamble of drilling a deep well."

What was learned from structure drilling was enough to whet the appetite but not enough to place any bets, Zimmerman went on, as a porpoise, arched up off the starboard beam and slid away again. "So we took another hard look, back around 1950. We made a seismic survey, setting off a series of artificial earthquakes in the water so we could record the echoes and learn the shape and depth of the rock layers below.

"We used a surveying boat equipped with radar for precise ranging. We used a recording boat to tow the sensitive seismometers to pick up the echoes. We used a shooting boat to suspend a nitramon charge five feet beneath the surface of the water. Each time we blasted off, a geyser shot out of the Gulf, just like Old Faithful."

The seismic work confirmed the structure drilling. Aramco now knew enough to gamble on the wildcat well that discovered the Manifa Field at the end of 1957. "So you can credit a combination of the structure drill and the seismograph with the discovery of this underwater field," Zimmerman said.

Sam was just on a busman's holiday. As a geophysicist—an earth physicist—he had long since completed his pioneering work at Manifa and had turned to farther reaches of Aramco's concession area in Saudi Arabia. But he wanted to see what had happened at Manifa since his days there.

Joe Turner squinted through the spray as he pointed a pudgy finger. "See that speck up there to the north? That's one of our wells." Nobody doubted that Joe could see that speck. He wanted to. As Aramco's offshore drilling foreman, he had drilled that well and had a paternal affection for it. But nobody else could really make out the Christmas tree—the cluster of fittings, valves and gauges which poked up a dozen feet out of the water, the only visible evidence of an oil well bored 8,000 feet down through the rock layers below the bottom of the Gulf.

"And down south there, looking into the sun? You can't see it, really, but there's another well, just over the horizon. I know, one of you visitors is going to want to shoot a pair of our wells on a single piece of film. You can't do it. They average three to four miles apart."

"How much of this stuff are you producing?" someone asked.

"Oh, we aren't producing any, yet," Joe replied. "Just a few samples for testing. We also used a little to oil that airstrip you saw back near the Manifa pier. But mostly, we're just drilling, just trying to find out what it is we've found, so Aramco can plan properly, can make the right decisions as to when and how to bring the field into production. We already know how far the field stretches on its western and southern flanks. The well you're visiting today will help mark the eastern flank. Then we'll go north. We're drilling what we call delineation wells."

From the drilling so far, Aramco knew that the oval-shaped field stretched at least 15 miles along its north-south axis and five miles across. Beyond the possibility of doubt, Manifa was a big discovery, although presumably not as big as the Safaniya Field, a little farther north, which was the first offshore field discovered in the Persian Gulf and the largest offshore field yet discovered anywhere in the world.

Admittedly, the initial drilling at Manifa was disappointing. The wildcat well, Manifa No. 1, was drilled more than a mile deep into the same sandstone that is so productive at Safaniya, only to find no oil there. Later on, that wildcat was carried down to nearly two miles through the most productive limestone reservoir in Aramco's onshore fields, only to find it water-logged. Sandwiched in between those two failures, however, Manifa No. 1 discovered not one but six reservoirs of porous limestone, all nestling into each other like a series of cereal bowls turned upside down, and all saturated with oil. These elongated bowls, known as anticlines, were the type of structural formation in which oil might accumulate. It was this sort of formation which the early structure drilling and seismic survey had revealed.

In three of these six rock layers Aramco had never before found oil anywhere in Saudi Arabia, either on land or at sea. The other three had previously proved only mildly productive in certain onshore fields. In none of the six reservoirs was the oil identical. It ranged from a heavy crude oil with a high fuel oil content, to a lighter crude with more gasoline. One of the six, the Manifa Zone, was the thickest layer and contained the most oil.

Now the helmsman was heading the water taxi's prow into the waves to moor alongside a broad-beamed lady officially carried on Aramco's books as Barge 136, but known affectionately as the Queen Mary. A little tug bobbed astern at the end of a long hawser, like a poodle on a leash. A few fishing lines hung limply, awaiting perhaps a tasty bass-like hamur, perhaps a speckled whitefish.

One of the passengers leaped on board, to be greeted by the roar of her diesel engines and the belch of her exhausts. The Queen wasn't putting on party manners for anyone. She was all business. Her measurements were a shapeless 174 by 70 feet, with squared-off bow and stern, but she was seaworthy enough to have survived a 10,000-mile tow from Lake Maracaibo in Venezuela. She was so plain and simple that little time was ever lost due to failure of fancy gadgets. She even slaked her thirst from the Gulf by distilling 50 gallons of drinking water every hour and by using sea water for mixing the drilling mud. All she asked was that her make-up be kept neat, by four men wielding paint brushes right around the calendar.

Proudly Joe Turner showed off, on the Queen's lower deck, the mud pumps, mud storage, shale shakers, laboratories, tool room, and, on the weather deck, the handling crane, casing racks, drill pipe racks, galley, two staterooms, anchor winches, even lifeboat. But the Queen was aging a little, and Joe had found a younger love. With an extra bounce to his step, he strode up the steep ramp connecting to a stately princess. She didn't have a nickname as yet, but she needed one, for who could wear such a formal title as "Aramco Mobile Drilling Platform No. 1?"

She was a floating island who, to mangle a metaphor, lifted herself up by her own bootstraps. When her trim triangular hull was floated into position for drilling Manifa No. 7, she jacked her three triangular legs of latticework steel down through the 36 feet of water and 19 feet of mud until they hit coral bedrock. As she kept stretching down her tripod legs, one foot per minute, her 800-ton hull rose slowly, like a huge elevator, until it cleared the surface of the waves by a good ten feet. Then she skidded into position her 136-foot-high drilling derrick from amidships to her stern, right over a little platform which in time would support a Christmas tree.

"Maybe she did cost us $1,000,000!" Joe Turner was shouting above the whine of the platform's rotary table. "Maybe it did take us 115 days to tow her from the LeTourneau works at Vicksburg, down the Mississippi, across the Atlantic, through the Suez and around the Arabian Peninsula. But she's paying off at $100,000 per well. We don't have to drive a steel pile platform, heavy enough to support the drilling derrick and drawworks, down to bedrock at each well location. We don't have to go to the trou-ble of erecting the derrick from scratch at each site."

Just then, the cry of "Yalla!" (literally, "Come on, with the grace of God!") split the air. The Saudi Arab driller, at the controls, stopped the mud pumps and slowed the rotary table to a halt. His ten-man drilling crew, all Saudi Arabs, had to "make a connection"—to add another 30-foot joint of steel drill pipe - before the drill bit could bore any deeper than the present 3,157 feet. Now a finely trained team weaved on and off the floor of the derrick as if they were on a basketball court. The driller hauled the drilling string 30 feet out of the hole. One rigger secured the drill pipe with the serrated teeth of the "slips." Others broke the connection between the round drill pipe and the square "kelly." The driller lowered the kelly into the "rat hole" for safekeeping. A rigman detached the hook from the kelly and attached the hook to a new joint of drill pipe. The driller raised the new joint, set it down on top of the drilling string, and spun the new joint in. Machine wrenches tightened the connection. Then the kelly was hooked on again, hauled out of the rat hole, spun into the new joint, and tightened with machine wrenches. The driller started up the mud pumps, lowered the whole drilling string and felt for the bottom of the hole.

The cry of 'Yalla!" provided a punctuation mark at the end of each step. With a final "Yalla!" the driller restarted the rotary table and resumed drilling—for another 30 feet.

Making the connection had taken only six minutes.

This article appeared on pages 16-19 of the June/July 1960 print edition of Saudi Aramco World.


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