French utility GDF Suez SA (GSZ.FR) has acquired independent oil and gas company Andarko Petroleum Corp.'s (APC) 60% stake in a Qatari offshore natural gas block, becoming an exploration and operation operator in the gas-rich country, the French company said Monday.

GDF Suez, which buys in most of its gas, has a target of eventually boosting its own reserves to 1.5 billion barrels of oil equivalent. That would involve doubling the company's reserves from the 704 million barrels of oil equivalent it held at the end of 2008.

"The acquisition is part of a strategy to increase the group's hydrocarbon reserves, notably through geographic expansion of its exploration and production activities," GDF Suez said in a statement.

Block 4 extends over a 3,132 square kilometer area off Qatar's coast and has "several prospects," GDF Suez said.

Qatar is the world's leading exporter of liquefied natural gas and has huge gas resources.

GDF Suez said it bought the stake in Qatar's offshore Block 4 through the purchase of Anadarko Qatar Block 4 Company LLC but didn't say how much it paid.

-By Adam Mitchell, Dow Jones Newswires, +33 1 40171756; adam.mitchell@dowjones.com