Oil Underwater Photograph by Sarah Leen One hundred twenty miles (200 kilometers) off the Louisiana coast, the drill ship Discoverer Enterprise prepares for production to begin at BP's Thunder Horse oil field in 2005. As six giant thrusters hold the ship in place, its crew punches wells into the seabed 7,000 feet (2,000 meters) below. With an estimated one billion barrels of crude, this field could represent the biggest discovery yet in the Gulf of Mexico. Developments in offshore drilling have allowed oil companies to work in deeper and deeper waters. The new world record—at 10,011 feet (3,050 meters)—was set in the Gulf in November 2003.

It's inevitable. But just how soon will the vital fuel become so scarce and expensive that we're forced to make hard choices about how we live.

Below more than a mile of ocean and three more of mud and rock, the prize is waiting. At the surface a massive drilling vessel called the Discoverer Enterprise strains to reach it. It's the spring of 2003, and for more than two months now the Enterprise has been holding steady over a spot 120 miles (200 kilometers) southeast of New Orleans in the Gulf of Mexico. The ship is driving a well toward an estimated one billion barrels of oil below the seafloor—the biggest oil field discovered in United States territory in three decades.

The 835-foot (255-meter) Enterprise shudders every few minutes as its thrusters put out a burst of power to fight the strong current. The PA system crackles, warning of small amounts of gas bubbling from the deep Earth. And in the shadow of the 23-story-tall derrick, engineers and managers gather in worried knots. "We've got an unstable hole," laments Bill Kirton, who's overseeing the project for the oil giant BP.

The drill, suspended from the Enterprise's derrick through a swimming-pool-size gap in the hull, has penetrated 17,000 feet (5,000 meters) below the seafloor. Instead of boring straight down, it has swerved more than a mile sideways, around a massive plume of rock salt. But now, with 2,000 feet (600 meters) to go, progress is stalled. Water has begun seeping into the well from the surrounding rock, and the engineers are determined to stem its spread before drilling farther. Otherwise, the trickle of water could turn into an uncontrolled surge of crude. "There's a lot of oil down there wanting to come out," says Cecil Cheshier, a drilling supervisor, after struggling all night with the unruly hole. "You can cut corners and take chances—but that could cost you a lawsuit or cause a spill into the Gulf of Mexico, and then deepwater drilling gets shut down."

The troubled well is just one of 25 that BP plans to drill in the giant field, called Thunder Horse, which sprawls over 54 square miles (140 square kilometers) of seafloor. The entire project, including a floating platform half again as wide as a football field that will collect the oil from individual wells and pipe it to shore starting next year, will cost four billion dollars. But if the wells live up to expectations, each will eventually gush tens of thousands of barrels a day. "That's like a well in Saudi Arabia," says Cheshier. "We hardly get those in the U.S. anymore."

You wouldn't know it from the hulking SUVs and traffic-clogged freeways of the United States, but we're in the twilight of plentiful oil. There's no global shortage yet; far from it. The world can still produce so much crude that the current price of about $30 for a 42-gallon barrel would plummet if the Organization of the Petroleum Exporting Countries (OPEC) did not limit production. This abundance of oil means, for now, that oil is cheap. In the United States, where gasoline taxes average 43 cents a gallon (instead of dollars, as in Europe and Japan), a gallon of gasoline can be cheaper than a bottle of water—making it too cheap for most people to bother conserving. While oil demand is up everywhere, the U.S. remains the king of consumers, slurping up a quarter of the world's oil—about three gallons a person every day—even though it has just 5 percent of the population.

What Lies Beneath Photograph by Sarah Leen The wellhead is just the tip of the iceberg at an oil storage cavern in Bryan Mound, Texas, where an employee of the Strategic Petroleum Reserve (SPR) does routine monitoring. Beneath the wellhead is an underground salt cavern the size of the Empire State Building. The SPR, the largest such reserve in the world, began operations in 1977 as an emergency crude oil storage site, ready to be drawn on should a disruption in commercial oil supplies pose a threat to the U.S. economy. Located at four sites in Texas and Louisiana, the reserve can hold up to 700 million barrels of crude oil. Should the need arise, a maximum of 4.3 million barrels of oil a day can be tapped from the reserve for 90 days. And delivery is swift. Once the President gives the go-ahead, oil can be on the U.S. market in 13 days.

Yet as the Enterprise drillers know, slaking the world's oil thirst is harder than it used to be. The old sources can't be counted on anymore. On land the lower 48 states of the U.S. are tapped out, producing less than half the oil they did at their peak in 1970. Production from the North Slope of Alaska and the North Sea of Europe, burgeoning oil regions 20 years ago, is in decline. Unrest in Venezuela and Nigeria threatens the flow of oil. The Middle East remains the mother lode of crude, but war and instability underscore the perils of depending on that region.

And so oil companies are searching for new supplies and braving high costs, both human and economic. Making gambles like Thunder Horse and venturing into West Africa and Russia, they are still finding oil in quantities to gladden a Hummer owner's heart. But in the end the quest for more cheap oil will prove a losing game: Not just because oil consumption imposes severe costs on the environment, health, and taxpayers, but also because the world's oil addiction is hastening a day of reckoning.

Humanity's way of life is on a collision course with geology—with the stark fact that the Earth holds a finite supply of oil. The flood of crude from fields around the world will ultimately top out, then dwindle. It could be 5 years from now or 30: No one knows for sure, and geologists and economists are embroiled in debate about just when the "oil peak" will be upon us. But few doubt that it is coming. "In our lifetime," says economist Robert K. Kaufmann of Boston University, who is 46, "we will have to deal with a peak in the supply of cheap oil."

Full story is available from National Georgraphic, June 2004 Issue