CAPE TOWN, June 26 (Reuters) - Sierra Leone will wait for the results of a recently-launched offshore 3D seismic survey, its first in over a decade, ahead of potentially opening its next oil and gas licensing round later this year, a senior government official said on Thursday.

In partnership with the government's petroleum directorate, consultancy GeoPartners started the six-week seismic survey last month as part of efforts to de-risk exploration in Sierra Leone's offshore basin.

"The reprocessing of that data is happening now with our multi-client partners, TGS, and we are hoping to get something to push to the market in October," Foday Mansaray, director general at the Sierra Leone Petroleum Directorate said of a potential licensing launch date.

He said the West African country, where the then Anadarko Petroleum and Russia's Lukoil previously discovered oil but not in commercial quantities, could potentially offer up to 60 offshore blocks in its sixth oil and gas auction round. The previous round concluded in 2023.

However, the new blocks are unlikely to include ultra-deep areas that are ordinarily open for direct negotiations, he said.

Sierra Leone has an estimated 30 billion barrels of oil equivalent recoverable offshore, Mansaray said, including the large Vega prospect identified by Anadarko previously, which has some 3 billion barrels of oil recoverable.

Situated along the Atlantic seaboard and between regional oil-producing countries, such as Ivory Coast to the south and Senegal to the north, Sierra Leone is keen to boost its credentials as an emerging exploration frontier.

Over the past 18 months, Shell SHEL.L, Petrobras PETR4.SA, Hess HES.N and Murphy Oil MUR.N have purchased some of its licensed data, Mansaray said.

Using Namibia and Guyana as examples of how exploration has boomed in those countries following years of inactivity, he said Sierra Leone could be on the verge of a breakthrough.

"I firmly believe that Sierra Leone is on the cusp of something big and we are going to be one of the next big and successful stories."

(Reporting by Wendell Roelf. Editing by Mark Potter)

((wendell.roelf@thomsonreuters.com; +27 21 461 3523;))