The company is project operator with 49% participating interest will manage the exploration and development project for the 4,022sqkm SL-5-11 deepwater block.

Lukoil vice-president Anatoli Katoshin told AFP, "We are going to invest $100 million in the first phase of an oil exploration venture in the first quarter of 2013."

Lukoil Ghana country manager Pavel Bogomolov said the company had built five wells so far in the Gulf of Guinea.

"Three in the Ivory Coast and two in Ghana and we are optimistic about the Sierra Leone drilling which will be 100km (62 miles) offshore," Bogomolov added.

Oranto Petroleum Corp. with 30% and Vanco Energy Co. with 21% are the other participants.

Sierra Leone announced its third offshore oil find when US-based Anadarko Petroleum Corporation struck oil in its Jupiter-1 well in February, earlier this year.