Big find, bigger thirst.

Byline: The Register-Guard

An oil strike announced by three companies last week is remarkable for two reasons. It's huge - 3 billion to 15 billion barrels. And it's deep - 30,000 feet beneath the surface of the Gulf of Mexico. The find promises to increase the United States' oil reserves by 14 to 70 percent and open the door to further ultra-deepwater drilling.

What it won't do is end the United States' dependence on imported oil. The new find is dwarfed by the scale of demand for oil in the United States and the world. This could be the biggest domestic oil strike since petroleum was found on Alaska's North Slope 38 years ago. But even such a discovery would not create a major shift in domestic or world supplies.

The world consumes 85 million barrels of oil a day, or 31 billion barrels a year. To avoid a drawdown of reserves, resources equal to those found deep beneath the Gulf of Mexico must be discovered every six months - and that's if the new field contains the high-end estimate of 15 billion barrels of oil. If the pool contains only 3 billion barrels, it will satisfy the world's thirst for six weeks.

The United States imported more than 12 million barrels of oil a day in 2005, or 4.3 billion barrels. The Gulf discovery could represent nearly four years' demand for imports at the 2005 rate. But the deepwater field can't be pumped right away, or all at once - daily production could eventually reach 750,000 barrels. That would have offset last year's imports by 6.25 percent. Domestic production is falling, however, while demand continues to rise. By the time the new Gulf oil begins to flow, it might bring imports back to their current level of about 60 percent of total consumption.

Nor will the Gulf strike alter the world supply picture. A 15 billion barrel discovery would add to the United States' petroleum reserves by 70 percent - a significant change. But it would add just 1 percent to world reserves. The United States ranks 11th in the world in petroleum reserves, with 21.4 billion barrels. The addition of 15 billion barrels would move the United States into a 10th-place tie with Nigeria. Sixty percent of the world's known reserves of oil would remain concentrated in the Middle East.

The United States' richest opportunities in the energy field lie not beneath the Gulf of Mexico, but beneath the hoods of cars and trucks. Two-thirds of the petroleum consumed by Americans is used for transportation. A 10 percent improvement in fuel efficiency would save 1.4 billion barrels of oil a year - an amount that would equal the Gulf discovery in two to 10 years, and the savings would continue indefinitely.

A conservation program that aimed to achieve a 50 percent improvement in transportation efficiency would save 7 billion barrels of oil a year. That's enough to cut current petroleum imports by half. It would amplify the importance of the Gulf discovery by allowing its daily production of 750,000 barrels of oil to represent a bigger share of total U.S. demand.

A 50 percent improvement in efficiency is ambitious, but not out of reach - it could be achieved with technology and investments far less impressive than those required to find oil six miles below the surface of the Gulf of Mexico. Such an oil discovery is good news for the country - but its rarity should harden a national determination to make oil resources last.