Lundin said its Norwegian subsidiary, Lundin Norway, started operations in the southwestern section of the discovery in the Norwegian waters of the North Sea.
Lundin completed an exploration well near the western edge of the Johan Sverdrup discovery in the North Sea in early August. Norwegian energy company Statoil last year estimated there were 900 million to 1.5 billion barrels of recoverable oil equivalent in Johan Sverdrup, twice the previous estimate.
The company said it was drilling to examine "uncertainties" related to the area's reserve thickness and quality.
"The well is expected to prove the existence of a producible oil zone and provide information for the planning of oil production from the south-western part of Johan Sverdrup," the company said in a statement Monday.
The company said it would take about 45 days to finish drilling the appraisal well. It said its appraisal program in the Johan Sverdrup field was "extensive."