As Russian forces have moved to cement the apparent will of Crimean voters, in the process taking over Ukraine's naval headquarters on the peninsula, two key questions have bobbed to the fore: 1) Will Vladimir Putin and his minions extend their sweep farther? 2) Could ExxonMobil (XOM 0.57%) become a forceful weapon for the U.S. in dealing with Russia's expansionary appetite?

A semi-submersible rig working under a contract with ExxonMobil.

The response to the first query is simply a matter of opinion, although most of those opining on the telly or in print these days clearly believe that Crimea is simply the first step for an ambitious Russian regime. The second question is somewhat more vexing. As you know, about two years ago Exxon and Russia's state-controlled oil behemoth Rosneft signed a series of joint venture agreements with each another. A loggerheads status between their respective countries clearly wouldn't benefit either company.

One-way technology sharing
The agreements were billed as an opportunity "to share technology and expertise." In reality, however, it's noteworthy that those two elements are flowing almost exclusively from Exxon to Rosneft. The latter company's contribution consists largely of potentially massive amounts of oil and gas in as-yet unexplored territories. For instance, Exxon obtained an opportunity to pony up with Rosneft in exploring the Kara Sea of the Russian Arctic, along with portions of the Black Sea.

Conversely, Rosneft gained interests in 20 blocks owned by ExxonMobil in the Gulf of Mexico, along with an equal stake in a Permian Basin project. It also became a partner of Exxon in Alberta's Cardium Shale formation. In 2013 the two companies returned to the bargaining table, from whence Rosneft emerged with an interest in Alaska's Point Thomson natural-gas field. For its part, ExxonMobil also got entry into shale basins in Western Siberia.

Are tighter sanctions likely?
But what if a scenario emerges wherein, with Crimea under its control, Russia moves to occupy another of its neighbors -- the Baltic nation of Estonia gained some mention at midweek -- and NATO's members tighten the meager sanctions they're already imposing against the Russian bear? Obviously a number of Western companies would be affected. Chevron (CVX 1.20%), for instance, is a major investor in the Caspian Pipeline Consortium and a significant supplier of lubricants additives in Russia.

And Schlumberger (SLB -0.68%) provides products and services to the country's oil and gas companies. Beyond that, it operates a research and development facility in Russia.

But ExxonMobil would obviously be affected the most. But its CEO Rex Tillerson recently noted, "There has been no impact on any of our plans or activities at this point, nor would I expect there to be any, barring governments taking steps that are beyond our control."

Tillerson's assessment is accurate to a point, or at least as it relates to Russia. In actuality, however, his company heads a consortium whose objective is the exploration of Ukraine's portion of the Black Sea. Plans for that group, which had included Royal Dutch Shell (RDS.B) -- until the company bowed out in January -- have been put on hold. Exxon already has a massive gas find to its credit in the Black Sea's Romanian portion.

Severely wounding Russia's economy
Russia's ambitious energy program (easily the most important sector of its economy) would clearly be affected more severely by stronger sanctions than would any of the Western companies. The country is woefully inadequate in its mastery of energy operations and technological sophistication. It almost certainly would be unable to proceed on its own.

Among the indicators of its laggard status was a late 2012 accident during which a Russian rig, the Kolskoye, was being inappropriately towed from Sakhalin Island through a winter storm. When its water discharge systems were overcome, the unit sank in the icy waters of the Sea of Okhotsk, costing dozens of lives. As The New York Times said at the time, "Though the Russian rig ... was not drilling when it sank, the accident was a setback for Russia's ambitions to expand offshore drilling to replace declining output on land, and maintain oil exports that are vital to the country's economy."

The Foolish takeaway
Whether or not there's a possibility of sanctions prohibiting Western oil companies -- especially ExxonMobil -- from participation in Russian joint ventures clearly will depend on Putin's determination to expand his trek across Eastern Europe. It's virtually certain, however, that such an edict would wound the country's vital oil and gas program severely.