Oil: A Beginner's Guide (Beginner's Guides) by Vaclav Smil

Oil: A Beginner's Guide (Beginner's Guides) by Vaclav Smil

Author:Vaclav Smil
Language: eng
Format: azw3
Publisher: Oneworld Publications
Published: 2008-02-01T05:00:00+00:00


OFFSHORE DRILLING

In 1949 John Hayward combined a submersible barge and a piled platform to build the first submersible rig, Breton Rig 20; he devised a way to stabilize a ballasted barge on the seafloor so that only the columns (connected to the barge and supporting the rig’s working deck) were exposed to waves. Kerr-McGee bought the rig in 1950, after it had drilled nineteen wells. A better version, Mr. Charlie, was built in 1953 by Alden J. Laborde who founded the Ocean Drilling & Exploration Company (ODECO). That company eventually combined with three other pioneers of marine drilling to form Transocean, the world’s leader in offshore engineering.

The first self-elevating (jack-up) drilling rig, Offshore Rig 51, began working in 1954. Its ten legs (1.8 m in diameter and 48 m long) ended in large spud cans to minimize the pressure of the ocean floor. A prototype of modern jack-ups – a triangular platform with three legs and pinions driven by electric motors – was built by Le Tourneau Company in 1956. Jack-ups were not suitable for deeper waters and in 1961 Shell Oil was the first company to deploy a semisubmersible rig, Bluewater I, in the Gulf of Mexico. Different designs followed in rapid succession – and a decade after the first model there were thirty semisubmersibles at work.

During the 1970s Transocean introduced the Discoverer-class drill ships whose operations proceeded to set repeated drilling records: by the year 2000 the fifth generation of these ships could drill in waters 3 km deep. By the end of 2006, there were roughly 650 mobile offshore rigs deployed worldwide, with more than 20% of them in US waters.

A new chapter of offshore drilling began with operations in very deep water. The industry defines work at a depth of 1,500 m (5,000 ft) as ultra-deep drilling, and the Gulf of Mexico has the world’s highest concentration of such projects and associated records, including an exploratory well drilled in 2003 by Discoverer Deep Seas in more than 3,000 m of water. In 2004 there were twelve rigs drilling in the Gulf’s waters, five of them in depths of more than 2 km.

These efforts have been rewarded with regular new major deepwater finds, six in 2003, eight in 2004, and nine in 2005. On September 5, 2006 a consortium of Chevron, Devon Energy and Statoil announced some details of their record-setting explorations in the Gulf of Mexico. Their Jack 2 well was set 280 km offshore in water about 2.1 km deep and then penetrated more than 6 km before encountering oil at a total drilling depth of 8.45 km. And this was no ordinary discovery: preliminary estimates credited the field with reserves of anywhere between 3–25 Gb, clearly a giant field and, if the higher total is verified, the largest discovery since the Alaskan Prudhoe Bay in 1968 and an impressive supergiant.



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