From my vantage point, three dominant changes in the world of oil and gas during, say, the past decade establish oil-field services giant Schlumberger (NYSE:SLB) as a compelling inclusion for any and all Foolish energy portfolios.

Of that trio of changes, two are technological, and the third is geopolitical. The first of the two based on developments in technology is the movement of exploration and production operations into significantly deeper waters. As one who once trod the halls of what today is Diamond Offshore (OTC:DO), I'll note only that much of the offshore activity until recently was centered in the Gulf of Mexico waters shallower than 300 feet.

Occasionally, as semisubmersible rigs became more common, operating in depths a few hundred feet deeper became somewhat commonplace. But drilling in up to 10,000 feet of water -- which today we consider relatively routine in such venues as the Gulf, Brazil, and Angola -- not long ago would have been dubbed a fiction straight out of Jules Verne.

Of course, you know about the other technology development: hydraulic fracturing, or fracking. Just five years ago there was concern in the U.S. about our likely soon-to-be-gone natural gas reserves. Today, thanks largely to the persistence of Houston-area oilman George Mitchell, whose company, Mitchell Energy & Development, is now owned by Devon Energy (NYSE:DVN), we virtually have more gas than we know what to do with.

NOCs take the lead
The third big change in the world of oil and gas, one that we don't think about as often as perhaps we should, involves the ascendency of the national oil companies (NOCs), and the consequent reduction in the dominance of the international members of Big Oil. Whereas ExxonMobil (NYSE:XOM) and its peers formerly held the lion's share of the world's proven oil reserves, fully 85% of that global cache is now in the hands of government-controlled companies like Saudi Arabia's Saudi Aramco, Russia's Rosneft, Brazil's Petrobras (NYSE:PBR), and Venezuela's PDVSA.

A key to picking energy stocks these days is the recognition that all three of these trends are likely to strengthen in the years to come. Sure, fracking will continue to be an environmentally induced political target. And ultra-deepwater drilling heightens the possibility of accidents like BP's (NYSE:BP) tragic 2010 Gulf of Mexico mishap. But in the final analysis, these changes are hardly likely to be reversed, thereby expanding the relative attractiveness of Schlumberger.

Doling out the dollars
The King Kong of oil-field services has two very important features going for it: First, its research and development expenditures, near a whopping $1.1 billion annually, leave little room for contention that the company isn't the industry's technological leader. Second, the company's scope, which includes a "crew" of 115,000 toiling in 85 countries, provides it with muscle in dealing with frequently sharp-elbowed NOC leaderships.

As to the sustainability of its leadership in technology, Schlumberger operates fully 25 research and development facilities worldwide. In addition to providing a familiarity with local and regional geological and other idiosyncrasies, this array, which includes centers in Brazil, Saudi Arabia (near the campus of King Fahd University of Petroleum and Minerals), and Russia also allows the company to operate at the proverbial back door of some of the world's most important NOCs.

The offshore's big splash
It's also worth noting that, with most of the world's major oil finds now occurring offshore, Schlumberger is active throughout the discovery-to-production spectrum in virtually all the waters of the oil and gas world. At the beginning, it's industry-leading seismic operation -- which benefits significantly from its emphasis on research -- involves it at the earliest stages of exploration. Later on, its technological sophistication stands it in good stead in the rapidly developing world of subsea systems.

Further, the company benefits from partnering with others, such as its venture with Petrobras to study pre-salt reservoir development. And just a week ago, Schlumberger and Cameron International (NYSE:CAM.DL) announced the formation of a joint venture, OneSubsea, which will develop and manufacture products and systems for the subsea oil and gas market.

The Foolish takeaway
Let's conclude with a look at Schlumberger's short-term earnings outlook. The company updated investors slightly more than a week ago, indicating that, based on contractual delays and higher-than-expected seasonal slowdowns, along with the anticipated sluggishness in the U.S. onshore market, results for the fourth quarter of 2012 are likely to be substantially below prior expectations.

Nevertheless, while Schlumberger's shares slid by 5% on the day of that announcement, they're clearly moving back to earlier price levels, Friday's soft market notwithstanding. More importantly, the one-year consensus price target for the company's shares among the analysts who follow the company is $90 per share, a nearly 30% leap from Friday's close. Longer term, if there's a long-term energy situation that's more attractive than Schlumberger's, I'd love to know about it.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.