"China's biggest oil firm, PetroChina, says it has made the country's largest crude discovery in a decade." -- BBC News

"China has made its largest oil find in more than three decades ... " -- Forbes.com

"Shares of PetroChina Co., the nation's top oil producer, surged after the company announced China's biggest discovery in half a century." -- Bloomberg

Golly, sounds like they found a lot of oil over there in China! Unfortunately, no one seems to be able to tell us how much -- with any accuracy, that is. All the media outlets seem eager to throw high-end estimates out there, in a similar fashion to what we saw with Chevron (NYSE:CVX), Statoil (NYSE:STO) and Devon's (NYSE:DVN) Jack-2 well test in 2006. If you recall, that's when it was reported that the deepwater Gulf of Mexico was believed to contain potential reserves up to 15 billion barrels, equivalent to roughly half the nation's reserves at that time.

So America has been cured of its dependence on foreign oil as a result of that discovery, right? No, the headlines didn't go that far. US crude oil demand is sitting around 20 million barrels per day, so aggressively assuming that 15 billion barrels are recoverable from the lower tertiary play, that would hold us over for, oh ... two years. We're saved!

Turning to PetroChina's (NYSE:PTR) Jidong Nanpu field, we are hearing a similar clamor over the discovery's potential to ease China's dependence on imports. Frankly, I just don't see it. Proven reserves are pegged at about 3 billion barrels, and out of that amount, most analysts are estimating that only about one-quarter is likely to be recoverable. If China's crude-oil demand somehow flat-lined at present levels of approximately 6.5 million barrels per day, Jidong's production would appear to satisfy about four months of Chinese demand. Of course, Chinese crude consumption rose 14.4% last year, and the possibility of demand topping out at present levels is remote.

Now, this is undoubtedly a valuable find for PetroChina. The shallow pay will make the reserves much easier to extract than those sitting about 5 miles under the deepwater Gulf's surface. The moderate boost in shares since the announcement seems reasonable, but I wouldn't go chasing the stock here. Production is several years away, and the company is likely to experience muted near-term profit growth in the face of higher drilling costs as it ramps up spending 25% this year. This one find is not enough to place PetroChina among the ranks of world-class explorers like ExxonMobil (NYSE:XOM) or BP (NYSE:BP), and it is too early to determine whether future exploration is likely to yield a satisfactory return on capital.

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Fool contributor Toby Shute welcomes your feedback. He doesn't own shares in any company mentioned. The Motley Fool has a world-class disclosure policy.