Somewhat quietly, but very importantly, the world of Big Oil is undergoing some big changes.

Going down
The first of these changes I've discussed with you in the past. It involves a movement by the bigger companies into progressively deeper offshore waters and difficult drilling conditions. It's a phenomenon that was discussed last week in a lengthy Wall Street Journal article. And as you know by now, the hottest areas of deepwater activity for the industry includes Brazil's Santos Basin, where the country's state-owned oil company Petrobras (NYSE:PBR) is the leader of the pack.

Other areas of increasing deepwater attention include the U.S. Gulf of Mexico, where, as the drilling rigs have been dragged into deeper water, the discoveries have become more sizable. Indeed, just this past summer BP (NYSE:BP) led a group that drilled what may have been the world's deepest well in the Gulf. The results of the effort are still being evaluated, but they clearly represent a humongous find.

The lurking dangers
And then there's West Africa, where a number of deepwater venues, including Nigeria, Angola, and now Ghana are proving to be fertile grounds for discoveries of black gold.

All too often, however, violence is also part of the energy scene in those countries. Just last week, an attack on a Nigerian pipeline took 20,000 barrels out of Chevron's (NYSE:CVX) daily production.

And with oil-rich Angola playing host to an international soccer tournament, Africa's Cup of Nations, the team from Togo was hit by machine-gun fire during a bus trip through a portion of the country, killing several passengers. While violence hasn't yet directly affected Angola's energy output, it may be because most of the country's production lies offshore, and thereby enjoys a built-in buffer.

Recent discoveries in Ghana likely have occurred at the eastern edge of a huge structure that stretches offshore from that country westward to the Sierra Leone, as far as 700 miles away. Attractive enough to make historically conservative ExxonMobil (NYSE:XOM) pay Kosmos Energy $4 billion for its stake in the Jubilee field. So while violence may never be eradicated on the continent, as each day passes, Sub-Saharan Africa's potential as a supplier of a sizable portion of the world's oil becomes more apparent.

The new unconventional world
Far from these deepwater efforts, an entirely different world has been emerging during the past several years. It's the changing world of natural gas production, a world that could radically change the dynamics and geopolitics of the energy scene over the next couple of decades.

It wasn't long ago that even the most grizzled veterans and sophisticated scientists in the U.S. oil and gas industry were convinced that we were rapidly coming upon the day when we'd, become a large net importer of gas. Traditional approaches to finding and producing gas were yielding less and less of the fuel source, which is used in power plants and home heating, along with a host of other applications.

But in places like Texas, Louisiana, Arkansas, Pennsylvania, and New York, an effort was taking shape -- led by a host of small and medium-sized companies like Chesapeake (NYSE:CHK) -- that stood ultimately to turn a potential paucity of gas into an abundance. In places like the Barnett Shale of the Dallas-Fort Worth area, along with the Haynesville Shale at the Texas-Louisiana border, and the Marcellus Shale, which covers much of the Northeast, the companies were discovering how to unleash the gas from hard, dense shale rock, where it had been trapped since time immemorial.

An underground charge
Their approach involved the development of new technology, horizontal drilling, combined with hydraulic fracturing, or "fracking." The latter involves exploding the shale and forcing large amounts of liquids and sand down the well bore to retain fissures in the shale, such that the gas can flow freely. The result has been an immense increase in the amount of natural gas available in the U.S.

Notice I said that the advances in the so-called unconventional gas plays had been primarily the work of the small and medium-sized companies. That, coupled with Big Oil's deepwater efforts has created an acquisition trail, where the deep drilling offshore and the shale gas plays on land stand to be united. You, of course, are aware of Exxon's recent decision to pay $31 billion for Fort Worth-based gas producer XTO (NYSE:XTO). There have also been shale deals between Chesapeake and both BP and France's Total (NYSE:TOT).

Balancing act
In my humble opinion, gas represents our ultimate energy future. It's cleaner-burning than coal or oil, more dependable than wind or solar, and our supplies lie in our homeland. Beyond that, it has tremendous potential as a transportation fuel. As such, we've likely just scratched the surface regarding the array of deals that will see the bigger companies attempt to attain a progressively more important balance between oil and gas via acquisition of their smaller, gas-prone brethren.

For now, it seems that Exxon should be credited with the lead in the oil-gas balancing act. And while other companies, such as BP and Chesapeake, deserve close scrutiny, I'm still a fan of the biggest of the big.

Exxon is a four-star company in the Motley Fool CAPS world. I suggest you add your opinion on this huge company.

Chesapeake Energy is a Motley Fool Inside Value pick. Petroleo Brasileiro and Total SA are Motley Fool Income Investor selections. The Fool owns shares of Chesapeake Energy and XTO Energy. Try any of our Foolish newsletters today, free for 30 days.

Fool contributor David Lee Smith doesn't own shares in any of the companies mentioned above. He does welcome your questions and comments. The Fool has an ironclad disclosure policy.