As a boy growing up on the Florida Keys, I lived for a couple of years next to Ted Williams, Beantown's fabuloso left fielder and hitter extraordinaire. For that reason, I tend to limit the number of residents of my pantheon of heros. But a current one, Texas oilman and energy hedge fund maestro Boone Pickens, may have quietly seen his sobering predictions about energy's future boosted somewhat by ExxonMobil's (NYSE:XOM) latest quarterly results.

On Thursday, the company reported that its net income slid in the quarter to $9.41 billion, or $1.70 per share, from $10.49 billion, or $1.77 a share, last year. And as you and I both knew would happen, given the across-the-board squeeze on refining margins in the quarter, the downstream contribution slipped 28% in the U.S. and nearly 26% elsewhere. No real surprise there.

But the scribes are already making far too much of the company having chalked up gross sales of $102.3 billion. Yes, that's a huge number. But to my way of thinking, the company's most significant figure was somewhat buried in its operating results: For the quarter, its worldwide liquids production declined by slightly more than 4%. If you bundle oil and gas together to achieve an oil-equivalent basis, the decline was about 2%.

According to a statement by the company, "Mature field decline and reduced entitlements were partly [emphasis added] offset by increased production from projects in Africa and Russia." Of course, you also have to factor Venezuela into the equation, since that country's President Hugo Chavez sent Exxon packing earlier in the year, along with the likes of ConocoPhillips (NYSE:COP), BP (NYSE:BP), and France's Total (NYSE:TOT). But overall, I'm inclined to focus on the first three words in the company's statement -- "mature field decline" -- as being perhaps the most significant.

Pickens has roamed the world discussing his notion that the approximately 85 million barrels of crude oil that the world produces today is unlikely to -- indeed, can't -- be expanded meaningfully. This, despite projections that, pushed by the developing nations, the world will need as much as 120 million barrels a day in just the next couple of decades. The biggest reason for his pessimism is that same "mature field decline" that Exxon talked about.

So, Fools, I think that in the quarters to come, we'll need to watch the liquids production of Exxon and the other big oil companies very closely. During the past quarter, the company spent $5.4 billion in its worldwide quest for oil and gas, an 8% increase year over year. Let's hope it was enough.

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Fool contributor David Lee Smith doesn't own shares in any of the companies mentioned. He does welcome your questions or comments. The Fool has a carefully constructed disclosure policy.