It was certainly a busy week for Brazilian behemoth Petrobras (NYSE:PBR). First, the oil and gas giant shocked observers with its obese estimate of original oil in place at an offshore field. Enthusiasm then waned somewhat on Friday, as the firm announced less-than-stellar financial results. On balance, shares were well in the black for the week -- quite a feat, given that the Street ran with the blood of newborn asset-backed securities.

First, a few thoughts on the Tupi oil field discovery. You've heard the term Big Oil. Well, this was a Big Oil Find -- like "5 to 8 billion barrels" big. PetroChina's (NYSE:PTR) puddle has nothing on Tupi. It's also noteworthy that this offshore field isn't sitting on the sort of heavy oil that refiners like Valero (NYSE:VLO) buy at a discount. This is primo, light-gravity stuff.

Before they even popped the Peterlongo, government officials quickly removed 13% of the exploration blocks coming up for bid in the late-November lease sale. This will make it harder for CVRD (NYSE:RIO) to go gas hunting, because it was eyeing those very blocks. The move has also left StatoilHydro (NYSE:STO) scratching and hissing, but it reflects the reality of today's oil patch. National interests are front and center, and I can't imagine that Norway would behave much differently if it stumbled upon a massive deposit in the North Sea tomorrow.

While its future prospects are bright, Petrobras is still suffering the same growing pains as the rest of the energy elephants. Sure, the company ground out modest domestic production gains, which is better than Chevron (NYSE:CVX) could boast, but the beefy Brazilian is also spending a king's ransom in reais to maintain production growth. Lifting costs are up 10% year to date, even after excluding currency appreciation, and investments were up a whopping 35% in the quarter.

As with its Chinese analogue, Petrobras has a strong asset portfolio, and it's fast becoming one of the most important global energy players. Fortunately, the shares haven't attracted the same level of speculative fervor, and I imagine that shareholders will continue to be rewarded by holding on for the ride. I'd advise Fools to keep an eye on those expenses and make sure you're getting your money's worth as Petrobras' production profile evolves.

Petrobras and StatoilHydro are both Motley Fool Income Investor selections. You can discover other companies that will pay you to own them by taking a free 30-day trial today.

Fool contributor Toby Shute doesn't have a position in any company mentioned. The Motley Fool's disclosure policy is both deep and profitable.