HOUSTON, CHICAGO (Bloomberg) — A Norwegian drill rig owner is supplying Russian oil giant OAO Rosneft and Exxon Mobil Corp. with the kind of high technology that will be barred under US and European Union sanctions taking effect shortly.

Though the EU said it will deny export licenses for equipment intended for deepwater and arctic oil production, Rosneft’s six rig leases from Seadrill Ltd.’ s North Atlantic Drilling unit, signed July 29, appear to thwart sanctions intended to block Russian oil companies from obtaining Western drilling expertise. Seadrill’s unit can proceed with the Rosneft contracts, worth $4.25 billion, because they were signed before the sanctions take effect, said Rune Magnus Lundetrae, Seadrill’s CFO.

The drilling contracts show how the latest round of international sanctions may have only minimal impact on Russia’s oil industry, at least in the short-term.

“This is not exactly a full, frontal assault on the Russian economy,” Frances Hudson, who helps oversee $305 billion as global thematic strategist at Standard Life Investments, said in an interview from Edinburgh. The sanctions “are just nibbling around the edges” of Russia’s energy sector.

The EU and the US decided to tighten sanctions against Russia over its support of separatists in eastern Ukraine. The measures target the banking, energy and defence industries, threatening business in Russia for companies from BP Plc to Siemens AG and Renault SA.

It is initially unclear how sanctions might affect Seadrill and its unit, North Atlantic Drilling Ltd., since they have roots in multiple countries. Seadrill owns 70 percent of North Atlantic Drilling, and the companies are controlled by billionaire John Fredriksen, a Norway-born Cypriot citizen whose nickname is the Viking King. Both companies are incorporated in Hamilton, Bermuda, and Seadrill lists its headquarters as London, while North Atlantic Drilling is managed from Norway. “We understand that the sanctions will be possibly valid from Friday, August 1, and apply to future contracts. And these contracts were signed July 29,” Lundetrae said yesterday in a phone interview.

Rosneft slid one percent to close at 223 roubles in Moscow. Seadrill was unchanged at 227.3 kroner in Oslo. North Atlantic Drilling gained 1.6 percent in New York to close at $9.75.

Norway is not part of the EU, though its government has signalled it will probably abide by the sanctions against Russia. Seadrill’s Lundetrae declined to comment on which laws the contracts might be governed by.

Rosneft was first to announce yesterday it had locked in its contracts with the Seadrill unit, which is a piece of the maritime empire controlled by Fredriksen.

“Entering into long-term offshore drilling agreements will allow Rosneft to ensure implementation of exploration and development of its harsh environment offshore license areas,” Rosneft chief executive officer Igor Sechin said in the statement.

Fredriksen has never shied away from geopolitical strife. The $16.7 billion shipping magnate started amassing his fortune in the 1960s trading oil in Beirut and leasing crafts to the US military in Vietnam, and in the 1980s running oil for Iran during its war with Iraq.