The world of energy, which is the largest sector of the S&P 500, continues to be a hotbed of activity -- and uncertainty. But crude prices haven't increased by 30% during the past year, private equity firms are showing limited interest in the sector, and even ExxonMobil (NYSE:XOM) isn't as visible as, say, Google (NASDAQ:GOOG). In other words, at times, the group can seem almost subterranean.

But let me offer the hopefully not too grandiose opinion that what happens in energy is of major importance to all Fools. And while I believe that the investment implications of the current geopolitical scene and the approaches being taken by the energy companies are of major investment significance, they're also meaningful from a lifestyle perspective -- if not for you, then for your children and grandchildren.

On that basis, let's look at a couple of this week's developments at ExxonMobil and then consider their likely meaning for energy and for your Foolish portfolio.

First, you should be aware -- if you're not already -- that ExxonMobil has announced plans to undertake more than 20 project start-ups over the next couple of years. The company hopes that these efforts will add about 24 billion oil equivalent barrels to its reserves, along with a million barrels a day to its base volumes.

That's not small potatoes. Given its size alone, Exxon doesn't really benefit from involving itself in insubstantial projects. So while the assumption that all these initiatives will qualify as mega-projects may be a bit much, it's a good bet that they'll all be sizable. The key is that ExxonMobil must make multiple big discoveries to keep its total reserves from sliding.

Further, The Wall Street Journal reported Thursday that ExxonMobil CEO Rex Tillerson recently met with Libyan leader Moammar Gadhafi regarding the possibility of the company helping Libya in "breathing new life into (its) giant but aging oil fields." As the Journal pointed out, when Gadhafi and Libya made nice with the U.S. in 2004, the country was removed from the list of rogue nations with which domestic companies were prohibited from dealing.

Both these bits of news constitute a look at one company's efforts to play a role in moving global crude production from its current level near 85 million barrels per day to the 120 million barrels per day we'll need when today's newborns are finishing college. Fostering growth of that magnitude clearly won't be easy. It'll have to occur in the face of slowing production in such places as the North Sea, Mexico, and the U.S. onshore.

And it'll also have to occur despite the frequently perverse efforts of the band of shaky characters who run many of the nations where oil is found. Case in point: We recently noted that ExxonMobil would quietly cede operational control of its projects in Venezuela, as demanded by that country's president, Hugo Chavez. It now appears that ConocoPhillips (NYSE:COP) and Chevron (NYSE:CVX) will do the same.

So, Fools, the world of energy is likely to be a thrill a minute during most of our lifetimes, and I therefore urge you to remain represented in the sector. In my opinion, any of the companies mentioned above are good places to start, as are oil service giant Schlumberger (NYSE:SLB) and perhaps deepwater drillers Transocean (NYSE:RIG) and Diamond Offshore (NYSE:DO).

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Fool contributor David Lee Smith does own shares of Schlumberger, but alas, he has no ownership in the other companies mentioned. He welcomes your questions or comments. The Fool has a disclosure policy.