Exploring a deep gusher

Exploring a deep gusher IT WAS almost like the setting of a bi-tech futuristic movie scene: powerful tug-boats hauling a massive platform into an angry open sea; a 23,000 tonne structure anchored to the seabed by mile-long steel tubes and an 'on the sea' quarter module housing 106 people. And mind you, this is no fiction; all this was done for Project Mars - the mission to tap the riches of the largest offshore oil depot ever found.

Ever since the Shell Offshore Inc, a New Orleans-based subsidiary of the petroleum giant Shell Oil Company, detected huge oil reserves deep in the Gulf of Mexico, it has been a story of implementation of a series of plans nothing short of brilliant technological breakthroughs.

The us government started to auction off drilling rights to the deep waters of the Gulf of Mexico in the mid '80s and Shell was one of the bidders. Led by Roger Baker, a deep-water geologist, company prospectors teed off with having seismic boats send sonic waves deep beneath the Gulf at a depth of about 1.3 kin. The reflected feedback was then translated into paper printouts that gave clues about the structure and composition of the seabed. Seismic lines appear like a plot of random squiggles to the untrained eye. But in the blocks Mississippi Canyon 763 and 807, Baker identified thicker and brighter spots which indicated that something different might lie below. Baker and Jim, Funk, Shell's offshore operations manager since 1986, then used advanced techniques of 3-D seismic imaging to decipher what really Jay beneath the seabed. A typical field in the Gulf contains oil at two or three depths, but the new-found site had the potential of more than a dozen layers. Shell geophysicist Mark Stockwell mapped the possible layers, and assigned each a colour. Orange and pink were the most promising but magenta, scarlet and other hues also held potential. "We ran into so many layers of interest that I ran out of colours," recalls Stockwell. It was named Mars because explorers suspected something astronomical.

Oil was finally struck at a depth of 4.1 km (the orange level). After initial celebrations, Shell was confronted with the biggest obstacle: how to retrieve the oil and how to send it onshore for refining? One option was to construct a behemoth, bigger than two Sears Towers put together, which would consume more than 25 million kg of steel and would cost a staggering us $3 billion. The other option, which seemed revolutionary indeed, was put forward by Daniel Godfrey, a civil engineer from Washington and a Shell employee since 1968. He envisaged that it would be easier to build : floating platform that moves with the wind and the waves'.

Twelve willowy yet superstrong steel fibres, each 28 inches in diameter and made of 1.2 inch thick steel, would stand vertically on the ocean floor keeping the platform - which floats like a cork in place. Each fibre would be fixed to the ocean floor by a 110 in long pile weighing 20,000 kg, and the piles would be driven deep into the ocean floor by hydraulic hammers. The structure, however, would have to withstand hurricane winds at 240 km an hour, waves more than 20 in high and wear and tear of the ricochet of more than 200 million waves during its estimated lifespan of 35 years.

The idea was tested with a model 1/55th the size of the real thing in a 20 in deep swimming pool at the Offshore Technology Research Centre at Texas A&M University. Twenty giant fans were switched on producing a gale with windspeeds reaching 200 kin an hour and artificial wavemakers were employed to create giant waves. Godfrey's model passed with flying colours.

The real model was modified keeping in mind all the conditions it would fa4@e. Like a skyscraper, it would have to move to prevent snapping and the support tubes vertically beneath the platform were strengthened by a network of giant, hollow tubes - laid deep inside the ocean floor - acting as pontoons. Underwater maintenance checks would be carried out by remote controlled robots as the pressure at such a great depth would be too much for divers to handle. After all, it is the deepest ever human-made structure.

Completed in Italy, the structure, headed for the high seas in mid-April and by summer, 1997, would yield almost 100,000 barrels of crude oil a day, which is more than 1.5 per cent of the annual us production of oil. Estimated at us $650 million, the Project Mars should break even, experts say, by sometime in 1998.

Shell's success in the Gulf has sparked a surge in deep-water drilling around the globe. There are *w some 18 major projects underway in the Gulf. Mars has also spurred the industry onto stepping out deeper into the waters of Norway, Nigeria and Brazil.