A Russian consortium has paid $1 billion to Venezuela to assure participation in exploiting the Orinoco oil fields, among the world's largest, officials said Sunday.

A Russian consortium has paid $1 billion to Venezuela to assure participation in exploiting the Orinoco oil fields, among the world's largest, officials said Sunday.

The group of five Russian firms -- Rosneft (ROSN.RS), Lukoil (LKOH.RS) Gazprom (GAZP.RS), TNK-BP (TNBP.RS) and Surgutneftegaz (SNGS.RS) -- paid "for access to exploit the reserves with us," the South American nation's energy minister, Rafael Ramirez, said, Ramirez said on President Hugo Chavez's radio show.

On Saturday Venezuela's state oil company Petroleos de Venezuela (PDVSA) said production on the massive Junin 6 heavy crude oil block would begin by 2012, and that the Orinoco-based operation would produce "between 400,000 and 450,000 barrels of crude a day."

Junin 6 is estimated to hold 53 billion barrels of heavy crude, making it one of the world's largest reserves.

Chavez, leader of the largest oil exporter in South America and a founding member of the Organization of Petroleum Exporting Countries, said that during his visit to Moscow last week he signed the joint venture that would give PDVSA a 60% stake, with the remaining 40% to the consortium.

The deal foresees investments of nearly 30 billion dollars in the project, Chavez said on his radio show, "Alo Presidente," adding that the operation could surge to up to a million barrels per day.

Oil-rich Venezuela claims current proven reserves of some 142.3 billion barrels, but expects to raise that total to as high as 316 billion barrels. Of this total, 235 billion are estimated to lie underneath the Orinoco.