KNOC won rights to 65 percent of production from the two blocks in the Gulf of Guinea by exercising special pre-emption privileges that the Nigerian government had granted to it in the past week. Bids from Chevron and Exxon Mobil were disqualified because they were incomplete.

The two blocks - officially known as 321 and 323 - have, according to seismic data, the most promising oil and gas reserves among the 14 deepwater blocks Nigeria auctioned Friday and Saturday in Abuja, the national capital. Increasing energy demand in growing Asian nations is driving governments to secure crude and gas supplies in new territories.

Edmund Daukoro, Nigeria's top oil official, defended the decision to give KNOC preferential rights, saying Korea has promised to build railroads and power plants in Nigeria.

``Relationships between countries don't go in the cycle in which oil rounds come about,'' Daukoro said. ``If in the middle of planning a round Nigeria feels that it wants to have good economic relations with another country that promises to do major infrastructure projects, as a sovereign nation we have the right to do a package.''

The total value of KNOC's investments tied to its bids and related projects could reach as high as US$7 billion (HK$54.38 billion), said a KNOC official who declined to be identified. For its part, ONGC offered a US$310 million signature bonus to Nigeria as part of its bid, about US$100 million more than the closest rival signing bonus.