Halfdan Knudsen, a vice president in charge of developments on the Norwegian continental shelf, said the investment would help boost recovery by 65 million barrels of oil equivalent.
"By using the fast-track concept, with standardized solutions and consistent teams in one project, we will improve recovery in an effective manner," he said in a statement.
The company said parts of the field were closed in 2008 in order to maintain pressure levels at the site for future drilling operations. Pressure in mature fields like Gullfaks declines as production occurs.
Statoil last year estimated there may be as much as 9.5 million barrels of recoverable oil equivalent present in the Gullfaks area.
Resumption of operations at Gullfaks South is expected in 2014.
"We're now making a substantial investment in a mature field," Jannicke Nilsson, senior vice president for the operations North Sea west cluster, said in a statement.