Lukoil Overseas, a subsidiary of Russia's second-largest oil company, said a 3-D seismic survey was under way in a 700-square-mile section of the Romanian waters of the Black Sea.
The company said the survey marks "the first time in its history (that) Lukoil has begun upstream operations in a European Union member country."
Lukoil said it was conducting the survey in preparation for work in the East Rapsodia and Trident blocks offshore Romania. Water depths range from 295-3,280 feet.
Lukoil didn't indicate the reserve potential of the two blocks offshore Romania.
Russian oil company Rosneft and Exxon Mobil signed a deal in August that included development in parts of the Black Sea and the South Kara Sea in the Russian arctic. There may be as much as 85 billion barrels of oil in the Kara Sea.
French supermajor Total announced it landed a similar deal for the exploration of a license area in the Bulgarian section of the Black Sea.