So they have used their dominant position in OPEC to act as the “swing” producer, raising and lowering production as needed to keep prices steady and to ensure that the oil age continues. But lately, their power has been threatened by surging world demand that has eliminated most of the gap between supply and demand. The Khurais field, they hope, will help restore that margin.

Image The Saudis say the Khurais oil field holds 27 billion barrels. Credit... The New York Times

Mr. Nasser and other Aramco officials described a project whose dimensions boggle the mind. Starting in June 2009, the field will produce 1.2 million barrels a day, enough to satisfy the expected growth in global demand next year. The Saudis say they are investing more than $10 billion, with 26 contractors, 106 subcontractors and 28,000 employees. It is the largest piece of a five-year, $60 billion effort to expand oil production capacity at a time of fast-rising demand.

A company tour of the main processing zone had a surreal, theatrical air. As the journalists stared out through the windows of their air-conditioned bus, hundreds of south Asian workers stopped work to stare back, their sun-protection masks and dark glasses making them look like Hollywood extraterrestrials. It was impossible to know if the site had been prepared for the journalists’ tour.

Beyond the buildings, gas flares blurred the horizon, in a forbidding landscape punctuated only by low reddish dunes and a few scattered shrubs.

The Khurais complex, which includes two smaller adjacent fields, was discovered in 1957. It got only limited use, because its oil is less accessible than that of the great Ghawar field, the world’s largest.

Now the Saudis are deploying an extraordinary engineering effort to bring Khurais’s mile-deep oil to the surface. Seawater will be carried through new pipelines from the Persian Gulf and injected into oil-bearing rock to pressure the oil upward. Usually Aramco pumps seawater into a field only after several years of production, and some skeptics point to this as a reason to doubt that Khurais will live up to its billing. But Mr. Nasser said the huge seawater injection system at Khurais was about cost and logistics, not a sign of a weak field.