As any Fool who has spent time researching energy investments knows almost instinctively, there's much to be said for taking positions in companies that operate at a level below the industry's biggest players. For instance among the producers, it's hard not to like Apache (NYSE: APA), which is unusually good at applying advanced technology to providing new life to otherwise tired and depleted oil venues.

At the same time, however, a top-down look at today's energy world will uncover challenges in virtually every aspect of this important sector. In short, the bigger your vessel, the less likely you are to be made queasy by stormy seas. For that reason among others, I'm inclined to urge those with a taste for energy investing -- and in today's world that should include all Fools -- to maintain a close watch on the industry's 800-pound gorilla, ExxonMobil (NYSE: XOM). (As recently as Thursday came the surprising -- but perhaps inevitable -- news that the Texas-based company has been surpassed as the world's leading publicly traded producer by 13-year-old PetroChina (NYSE: PTR).)

Rowing upstream
Beginning among Big Oil's integrated functions with the progressively more challenging effort at locating and producing crude oil, Exxon's size and technological expertise have permitted it to spread itself essentially around the planet. Beyond the onshore U.S. and the Gulf of Mexico, Exxon's oil minions can be found laboring from Canada to Brazil in the Western Hemisphere. They're also busy in several European locations; in Africa's Nigeria, Chad, and Cameroon; in Iraq and Abu Dhabi in the Middle East; and in Russia. I could continue, but you get the picture.

ExxonMobil's scope has permitted it to adopt an essential "don't tread on me" operating philosophy and to stand its ground when, for example, Hugo Chavez nationalized the efforts of a half-dozen of the world's majors in Venezuela's Orinoco basin several years ago. In addition, it's been far more successful than most in dealing with the inevitable shenanigans of Russian authorities as it plied its trade on desolate Sakhalin Island. In part as a result, it signed an agreement a year ago to join with Russian oil giant Rosneft in exploring that country's promising arctic waters, along with a portion of the Black Sea.

Turning on the gas
Moving to natural gas, which a host of industry observers (including yours truly) expect to become our primary fuel source in the years to come, Exxon has also benefited from its size and deep pockets. In 2010, the company was able to fork over $41 billion for Fort Worth's XTO Energy, an acquisition that added 45 trillion cubic feet of the clean-burning -- and currently dirt-cheap -- fuel to its coffers. That addition immediately thrust Exxon into the top position among U.S. gas producers.

Beyond its newfound U.S. gas supremacy, Exxon is participating in the massive, Chevron (NYSE: CVX)-led Gorgon LNG project off Western Australia. In addition, it's actively using horizontal drilling and hydraulic fracturing techniques in an attempt to locate natural gas in Poland's shale rock. If that effort proves successful, Poles will breathe a sigh of relief, having found a way to wriggle out from under the dominance of their current gas supplier, Russia's frequently bullying Gazprom.

Making do with minimal margins
And then there's refining and marketing, the "downstream" in the vernacular of the integrated oil companies. Others are being squeezed by tight margins between crude costs and refined-product prices to the extent that there are about as many refineries on the block as houses in Las Vegas. However, Exxon has no need to chop its complement of refineries. The ability to stand in there amid cyclical challenges is likely to benefit the company significantly when, as is inevitable, margins expand.

For now, ExxonMobil, like its smaller brethren, is attempting to deal with the Obama administration's pokey permitting process in the Gulf of Mexico, a circumstance that ultimately could trim U.S. production. As the New Orleans Times-Picayune said in an editorial last month: "President Obama has noted that domestic oil production is up. But production cannot be maintained or increased -- as the president has said he'd like to do -- if not enough new wells are being drilled."

Technology's the key
Finally, there's the progressively more important role of technology, where advancements have lately affected the oil and gas industry dramatically, especially on our continent. As Exxon's CEO Rex Tillerson told an industry group earlier this month: "The transformation unfolding in North America represents a potentially decisive shift in the history of energy. New technologies and innovative techniques developed by the men and women of our industry have taken sources of energy once labeled 'unconventional,' 'uneconomic,' and 'inaccessible,' and made them conventional, economic, and environmentally responsible."

The ability to maintain the role of a technological leader in the industry, along with oil-field services giant Schlumberger (NYSE: SLB) -- each of which spends a whopping $1 billion a year on research and development, will make possible the tremendous growth that the company envisions for traditional energy usage. Indeed, its forecasters predict that by 2030 -- the year that those born in 2012 will enter college -- global energy demand will expand by 30%, the call for natural gas will jump by 60%, and production from the deepwater will double.

It'll clearly take a company of ExxonMobil's scope and technological sophistication to lead the oil and gas industry in hitting those lofty targets. Beyond that, however, for my money all of the companies I've talked about merit your Foolish attention. I suggest that you add Exxon to your individualized version of My Watchlist:

Or if you're looking for more energy ideas, make sure to check out our free report, "3 Stocks for $100 Oil," which highlights three great companies that have a bright future ahead of them as energy consumption continues to increase around the globe. Get started for free!