Petrobras (NYSE: PBR) has a funny way of (not) making headlines. You'd think that a potential 33-billion barrel oil discovery would merit some monster PR, but instead the company has allowed the unconfirmed news to seep out slowly through unofficial channels.

The word on Carioca and Sugar Loaf, two fields that possibly comprise one and the same super-giant oil field off Brazil, just reached my attention in comments by a Brazilian energy minister on Monday. The official was apparently citing a February magazine article. Petrobras will neither confirm nor deny the figures flying about, and instead chooses to wait for more data to come in.

So what are investors to make of all this? It would be a mistake to draw too firm a conclusion about the number of barrels here. All the same, it's worth familiarizing ourselves with the four petroleum parcels in play.

The Carioca test well, which Petrobras has confirmed as a discovery, lies in a Petrobras-operated block in which Repsol YPF (NYSE: REP) holds a 25% stake. The Spanish company's humble slice was enough to generate a 9% groundswell in its ADRs yesterday. The Sugar Loaf well test lies in an adjacent Petrobras-held block, in which Royal Dutch Shell (NYSE: RDS-A) (NYSE: RDS-B) holds a handsome 40% interest. So did Shell shares surge by the seashore? Only a smidge.

There are two more blocks nearby, one of which is operated by ExxonMobil (NYSE: XOM) and counts stealthy offshore heavyweight Hess (NYSE: HES) as a significant minority partner. Test results there aren't expected until June, and it's impossible to say whether those companies will find themselves in the fairway.

Fortunately, one thing here is certain. Deepwater drillers like Noble (NYSE: NE) already are, and will continue to be, big beneficiaries of this Brazilian bonanza for many, many years.

Related Foolishness:

  • Here's another driller that might be to your taste.
  • This independent's actually lightening up on its deepwater fodder.
  • Brazil's big on biofuels, and you can bet that Petrobras will seek innovation in that space as well.

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Fool contributor Toby Shute doesn't have a position in any company mentioned. The Motley Fool has a disclosure policy.