Exxon Mobil Corporation (NYSE:XOM) is mulling bids for its Argentine shale assets as the US energy giant looks to unwind its bet on the South American nation's oil and gas riches. Exxon received several offers for holdings in Argentina's heralded Vaca Muerta formation in Patagonia earlier this month, according to people familiar with the matter. The assets, which comprise stakes it owns with QatarEnergy in seven oil-and-gas blocks in the shale patch as well as holdings in a pipeline, have been valued at around $1 billion, said the people, who declined to comment publicly on private talks.