Here we are walking on a tightrope, and most of us don't even realize it. That tightrope is nothing more than the dicey geopolitical situations in many of the places where the biggest reserves of crude oil are located.

And while we could probably list about half of the OPEC contingent as capable of precipitous unraveling, let's drop in on a couple of the exporting nations that seem to be teetering most precariously toward the sort of instability that could interrupt their production meaningfully.

We'll start off by heading south, Fools, and landing in Venezuela. Once there we'll discover that a host of the world's major oil companies, including ExxonMobil (NYSE:XOM), Chevron (NYSE:CVX), BP (NYSE:BP), Total SA (NYSE:TOT) and Norway's Statoil ASA (NYSE:STO) has -- as ordered by the Venezuelan government -- packed their duds and handed over operational authority in the nation's Orinoco reserve to the nation's government-owned oil company. The main risk from the nationalization program is that production of Orinoco's viscous crude could prove challenging to the nation's engineers. On Thursday, Venezuelan President Hugo Chavez announced an intention to also nationalize the banking and steel industries.

Only ConocoPhillips (NYSE:COP) has refused to sign an agreement officially transferring its operations, although it has ceased physically operating in the Orinoco. That legalistic recalcitrance could get it ejected entirely from Venezuela, but it's certainly the sort of pluck to be applauded.

Having glanced at teetering Venezuela, let's now head for Nigeria, another member of OPEC, where kidnappings and sectarian violence have followed the exclusion from high-paying energy jobs of members of tribes indigenous to the oil-rich Niger delta. The clear result is a threat to the nation's oil industry.

Indeed, from Tuesday through Thursday as many as 30 foreign workers were taken hostage in separate incidents. It further appears that at least 11 Daewoo Group employees are still being held, perhaps with physical mistreatment and the withholding of food. Korean Daewoo has evacuated nearly 200 workers from Nigeria as a result.

Between them, Venezuela and Nigeria export about 4.5 million barrels of oil daily. This says nothing about the 2.4 million barrels each day coming out of obstreperous Iran, or the 1.5 million barrels being shipped from war-torn Iraq. It doesn't even address the 7.2 million barrels a day being exported by OPEC kingpin Saudi Arabia, whose royal family isn't immune to geopolitical or religious treachery.

So, Fools, watch these unstable situations carefully. And as I've advised you repeatedly, please don't operate without energy representation in your portfolios.

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Fool contributor David Lee Smith doesn't own shares in any of the companies mentioned. He welcomes your questions or comments. The Fool has a disclosure policy.