But the government believes there is more oil and natural gas off the southern tip of the island.
"We want to survey the Southern seas and would be calling for tenders shortly," Petroleum Minister A H M Fowzie said.
"Sri Lanka is straddling oil bearing formations in the Middle East on one side and Indonesia on the other."
Though Sri Lanka is yet to conduct more expensive three-dimensional seismic surveys officials estimate that the Mannar basin to hold about one billion barrels of oil.
Surveys were done in 2003 and 2005. The TGS-NORPEC data was bought by Sri Lanka for about 10 million US dollars.
"We want to conduct surveys in the South, South West and South East of the island," the head of Sri Lanka's petrole