Investors are stepping up the hunt for hundreds of billions of dollars worth of oil beneath a deep submerged salt crust offshore West Africa, seeking to emulate Brazil's major discoveries across the Atlantic.

Geologists have long held that Africa's western seabed mirrors South America's. The continents were fused into a single plate nearly 200 million years ago.

Now, high oil prices consistently above $100 a barrel and cheaper technology make it possible for producers to explore thousands of feet below the surface.

The enthusiasm follows pre-salt finds by Total and Cobalt in Gabon and Angola, shifting focus to a region that has played second fiddle to east Africa's gas boom.

William Hayes, senior VP at explorer Kosmos Energy, told Reuters the firm expected a "suite of smaller, but still globally significant discoveries" in the region.

Jasper Peijs, BP's exploration director for sub-Saharan Africa, said he expected super giant discoveries off Angola.

"All the prospects there have the potential to be giant, which I would say is at least 250 million barrels and greater, or super giant of 500 million to a billion barrels and even greater than that," he said on the sidelines of an African oil and gas conference in Cape Town.

So far, most of the excitement has centred on Angola where prospecting is more advanced after a licensing round in 2011.

"The first year was one of acquiring seismic data, then evaluation of results and 2014 will be a year of drilling for most operators," Jean-Michel Lavergne, Total's General Director in Angola, said, adding that the company will drill two of the 10-15 pre-salt wells set to be explored in 2014.

In an interview with Reuters earlier this month, Angola's Oil Minister Jose Botelho de Vasconcelos said it could take operators eight to 10 years after discovery to start production.

Some expect the pre-salt zone to extend further north to the Republic of Congo and Equatorial Guinea or south to Namibia, stretching along a more than 2,000 kilometre coastline.

In addition to Angola, at least half a dozen pre-salt wells are either underway or have been announced in neighbouring Gabon and Equatorial Guinea.

Brazil has made several pre-salt finds since 2007 in the Santos Basin off its southeastern coast. It also has a host of new wells, such as the massive Libra field.

The International Energy Agency expects Brazil to become the sixth largest oil producer by 2035 and to meet a third of the net growth in global supply.

It said however that the pace of supply growth will hinge on the ability of its state oil company Petrobras to stick to its investment plans, which project $237 billion over five years, making it the world's largest corporate spending programme.

Wood Mackenzie's Martin Kelly, head of upstream research, estimated that total reserves in West Africa were between 10-15 billion barrels, or about a quarter and a third of Brazil's.

"The early signs are very encouraging that there will be commercial volumes of hydrocarbons," he said.