The development stages:In production - under development/2012-09.Argentina's Golfo San Jorge basin is principally being explored by Argentine oil and gas firms Pan American Energy and YPF. The companies hold the highest stakes in and own the greatest number of active wells in the basin. The basin totals some 200,000 square kilometers and holds 56.2% of the country's proven oil reserves and 9% of its gas reserves, according to data for 2007 provided by Argentina's energy department.