If you're worried about what the political turmoil spreading out from Egypt might mean for your energy investments, keep reading and I'll give you the names of two companies whose geographic reach and expertise make them strong candidates for your energy portfolio.

Investors are concerned about whether the turmoil in Egypt, Tunisia, Jordan, and elsewhere will roil its way into Saudi Arabia, the world's largest oil-producing nation.

While Saudi Arabia's King Abdullah bin Abdul Aziz "instructed" President Obama that there would be "no compromise" affecting Egypt's stability and security, it appears many everyday Saudis are pulling for the Egyptians in the streets. And so the world's largest oil-producing nation may not be totally out of the woods regarding a potential spillover from Egypt.

Meanwhile, so-called brent crude -- which is derived from the North Sea -- climbed above $100 Monday, the highest it's been since 2008. At the same time, West Texas Intermediate is sitting near $92, based on an abundance of supply.

What, then, do we do about energy investments during this time of uncertainty? Should we avoid them altogether? Of course not. Should we load up on the likes of ExxonMobil (NYSE: XOM) or, say, Chevron (NYSE: CVX) and ConocoPhillips (NYSE: COP)?

Don't avoid the big guys
It's hard to discourage Fools from plunging, or at least inching, into Big Oil. ExxonMobil has pulled out its ample wallet, made a couple of key acquisitions, and is rapidly transmogrifying -- we say that a lot in Tennessee -- itself away from its oil-dominated past and toward an increasing global presence in natural gas. It's now the largest gas producer in the U.S., along with being a partner with Chevron and Royal Dutch Shell (NYSE: RDS) in developing Australia's huge Gorgon liquefied gas project.

But think about this: As The Wall Street Journal pointed out last week, in the late 1960s, about 85% of the world's oil and gas reserves were under the wing of the major companies -- Exxon, Shell, etc. But now, believe it or not, that share has plummeted to just 15%. The lion's share now belongs to state-owned or state-controlled companies like Saudi Aramco and Russia's Rosneft.

Some of those countries are willing to work with the traditional Big Oil companies. For instance, Rosneft has just salted away separate joint ventures with BP (NYSE: BP) and Exxon. But many of the companies are beholden to governments that don't always represent the height of stability. Indeed, you may have noticed that, along with Egypt's uproar, there were admittedly smaller demonstrations in Moscow Monday demanding the ouster of Vladimir Putin.

On that basis, I think it's sensible to include in your portfolio companies with a wide geographic spread, whose assistance is needed by companies from the small independent producers to biggies like Aramco and Russia's Gazprom. That's especially important during times of geopolitical instability, like the present.

You can probably tell that I'm zeroing in on the two largest oil field service companies, Schlumberger (NYSE: SLB) and Halliburton (NYSE: HAL). Both of these Houston-based companies work around the world, including in progressively strengthening North America, but also in places like Mexico and Saudi Arabia, where Western oil and gas producers are corporate persona non grata. Even countries with sharp elbows resulting from intensifying resource nationalism are all too aware that they can't succeed without technological assistance from the big services providers.

Strong world travelers
Both companies are doing well. In the most recent quarter, Schlumberger, which includes an oil field services group and a seismic-oriented WesternGeco unit, expanded its earnings by 42%. Halliburton raised its reported earnings by a whopping 67%.

Just as importantly, Schlumberger's oil field services unit operates across the Americas -- including in increasingly active Brazil -- along with Europe, Africa, Saudi Arabia, Russia, and China. WesternGeco plies its trade in the Gulf of Mexico, Africa, and Australia, among other areas. Halliburton's completion and production unit and its drilling and evaluation segment also work globally.

The bottom line
It seems to me the key here is that with the world becoming more dicey by the day, the oil field service providers' geographic spreads and ability to work even for operators as recalcitrant as Hugo Chavez in Venezuela are essentially irreplaceable.

Chevron is a Motley Fool Income Investor recommendation. The Fool owns shares of ExxonMobil and Schlumberger. Try any of our Foolish newsletter services free for 30 days.

We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Fool contributor David Lee Smith doesn't own shares in any of the companies mentioned. The Motley Fool has a disclosure policy.