Shell is planning more seismic surveys of the seafloor off the coast of South Otago.
Shell New Zealand holds two deepwater exploration permits for the Great South Basin covering about 25,000 square kilometres.
At their closest, the areas come within about 50km of the coastline south of Dunedin.
The company is due to decide whether to begin test drilling for natural gas in one area by early January 2014.
Shell New Zealand said preview seismic mapping in two and three dimensions have indicated two potential natural gas accumulations it wants to explore further.
The company said it would begin a new set of two-dimensional surveying in January, running for about 70 days.