Back in 1968, Prudhoe Bay, the largest oilfield in the United States, was discovered in northern Alaska. It contained some 13 billion barrels of recoverable oil, and at its peak, it churned out 1.5 million barrels of black goo per day, adding a tidy amount to America's domestic oil production. What a treat that's been.

The problem is that bonanzas like Prudhoe Bay amount to a fraction of the oil we use. The U.S. imports the lion's share of its oil from foreign producers. That isn't breaking news to most people, but it typically gets passed off as a "thank-goodness-someone's-got-our-back" issue. However, check out the mushrooming tab that's being shipped off to our foreign-oil pals:

Year

Barrels Imported

Imported Oil Tab

2002

4.21 billion

$103 billion

2003

4.47 billion

$132 billion

2004

4.81 billion

$179 billion

2005

5.01 billion

$206 billion

2006

5.00 billion

$300 billion

2007

4.91 billion

$327 billion

2008 (estimate)

4.88 billion

$440 billion

The most recent 2008 estimate -- $440 billion -- assumes $90-a-barrel oil. With the current price hovering close to $140 a barrel, the figure becomes more like $683 billion. And if the price of crude were to hit $250 a barrel, as predicted by Russian oil giant Gazprom (OTC BB: OGZPY.PK), the figure balloons to well over a trillion dollars, but who's counting?

Well, Fools, in an economy with a GDP of around $14 trillion, sending anything close to $1 trillion to foreign countries isn't anything to sneeze at.

Here are three reasons why our dependence on foreign oil will be more than just a nagging issue for some time to come.

The neverending story
One problem with trade deficits fueled by oil imports is that they feed on themselves: the bigger the deficit, the weaker the dollar gets, and the weaker the dollar gets, the bigger the deficit can become. How so, you say? Shouldn't the weaker dollar push imports to decline? For many products, yes, but oil is different. There are few alternatives to oil, and consumption can't be reduced in short order. When oil goes up, our trade deficit goes up, and the dollar goes down. When the value of the dollar falls, companies that rely on cheap imports, like Wal-Mart (NYSE:WMT) and Dollar Tree (NASDAQ:DLTR), can really feel the heat as costs begin to soar.

What goes around, comes around Oil-exporting countries have to do something with all those dollars they accumulate. Where do a lot of them end up? As investments in U.S. securities. Of course, that helps in many ways, propping up markets that might be in even deeper water without foreign investors providing much-needed liquidity. For example, Citigroup (NYSE:C) grabbed a $7.5 billion lifeline from the Abu Dhabi Investment Authority last year. According to the Treasury Department, oil-exporting countries held $153 billion in U.S treasuries as of April, up 37.4% from the year before.

The problem arises when the benefits of those securities -- interest payments on debt, and dividends from stocks -- get siphoned out of the U.S. economy. I'm all for globalization, but when an ever-growing slice of our economic pie gets served up outside our borders, the benefits of our own labor become more and more distant.

Geopolitical woes
Whether it's a cause or an effect -- or even related at all -- some of the world's great oil reserves aren't located in the most politically sound regions. Some of the top oil-exporting countries -- Saudi Arabia, Nigeria, Venezuela, Iraq, Colombia, Russia, and Libya -- might not read like a "who's who" list of American buddies. Unfortunately, our economy relies on those countries more and more as oil prices soar. Case in point: ExxonMobil (NYSE:XOM), ConocoPhillips (NYSE:COP), and Chevron (NYSE:CVX), just to name a few, learned the hard way about operating in oil-rich foreign lands when Venezuelan President Hugo Chavez tightened his nationalization grip, forcing a handful of American companies to take a hike. His gain, our loss.

Where do we go from here? Like most things that look unbelievable, a trillion-dollar imported-oil tab might be economic fearmongering at its best. And if the price does happen to get that high, it's unlikely to stay there very long. But that's not the point.

Instead, realize this: The burden of oil contains more landmines than just higher prices at the pump. Gas-tax holidays, windfall profit taxes, and OPEC production increases may or may not alleviate gas prices, but they’re almost guaranteed to do precisely nothing to wean the economy off foreign oil.

Let the games continue.

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This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.