Tullow Oil announced another huge oil discovery in Uganda yesterday, delivering a fresh boost to the African state’s hopes of becoming a significant oil producer.

The Ngassa-2 well in the Lake Albert region could be the largest oil discovery in Uganda to date, Tullow said. So far, the company has drilled 27 wells in the Lake Albert rift basin, which lies along Uganda’s western border with the Democratic Republic of Congo (DRC), and has discovered oil in 26 of them.

Angus McCoss, exploration director at Tullow, said the discovery of a significant oilfield at Ngassa, which could extend across an area of 150 sq km, might be the biggest of them all and represented a “major achievement”.

He declined to say how much oil it might contain, but analysts believe it could be as high as 600 million barrels. If confirmed, that would nearly double the 700 million barrels that Tullow has already found elsewhere in the Lake Albert basin.

The discoveries promise to transform Uganda into one of Africa’s largest oil producers and may prompt the industrialisation of a now remote corner of the continent.

While the Tullow discoveries are enormous, the cost and complexity of developing them will be equally so.

The crude found around Lake Albert, which lies 250 km north west of Kampala, the capital, is thick and sludgy — so-called heavy oil — and is difficult to transport.

Two options are being considered to make the fields commercially viable.

One involves the construction of a 1,200km pipeline across large areas of swampland to Mombasa on the Kenyan coast, where the oil could be refined for export. However, President Museveni of Uganda has emphasised that he would prefer the oil to be refined within his country to ensure maximum profits. That could mean developing a refinery close to Lake Albert.

Tullow is seeking partners to help it to develop the finds. It is also considering selling down some of its 100 per cent stake in the Ngassa field.

A string of potential partners are eager to muscle in on the discoveries. BP, Royal Dutch Shell, Eni, of Italy, and several state-owned companies from China have expressed interest in the region.

Uganda has never before been a significant oil producer. Glada Lahn, energy researcher at Chatham House, the foreign policy think-tank, said that its Government faced a host of challenges if it wished to ensure that it does not suffer the “oil curse” of conflict and corruption that has affected other African countries such as Nigeria and Angola.

He added: “There is a risk that oil will distort the economy and present challenges to democracy in Uganda. Oil tends to bring with it a boom-bust cycle of development and a sudden flood of foreign currency could make its other exports less competitive.”

After the announcement of the discovery yesterday, the company’s shares rose 4 per cent to £12.38, giving it a valuation of £9.5 billion.

The latest news from Tullow — which started life in the 1980s as a small independent Irish oil explorer — of a fresh discovery in Uganda caps a positive week for the oil company.

On Wednesday, a consortium that includes Tullow announced another big oil discovery off the coast of Sierra Leone. The news captivated the markets, making Tullow easily the biggest riser of the day, the share price leaping 100p to £10.87.

The group, led by Anadarko Petroleum, of the United States, claimed that it potentially opens up a new, 1,100km-wide, multibillion-barrel oil frontier in West Africa.

Tullow’s shares have nearly trebled in price since December when they were trading at less than 450p.

Good news keeps on flowing for accountant turned explorer

For Aidan Heavey, it has been a fabulous run. The Irish accountant who founded Tullow Oil started out as a financial controller for Aer Lingus. In 1981 he joined Tullow Engineering, a small Irish company that had a subsidiary operating fuel tankers called Tullow Oil.

Inspired by the idea that the world was full of oilfields too small to be considered commercial by the multinationals, in 1985 Mr Heavey oversaw a buyout of the business with an ambitious plan to transform it into an independent oil explorer in Africa. He made his first play in Senegal, then the North Sea.

Since then, Mr Heavey, 56, has pulled off a series of shrewd deals that have built Tullow into a FTSE 100 powerhouse with operations in 23 countries on four continents.

Yesterday, Tullow Oil’s market value hit £9.5 billion as investors cheered the news of the discovery of vast new oilfields in two parts of Africa.

The defining deal for Tullow was the acquisition of Australia’s Hardman Resources in 2006, which gave it access to unexplored acreage in a remote corner of Uganda. That deal has turned out to have been spectacularly good value, unlocking a string of huge discoveries that have seen Tullow’s valuation soar.

Uganda is not the only place where Tullow has enjoyed good fortune. The company, now based in a business park in Chiswick, West London, is also enjoying a bonanza off the shores of Ghana and Sierra Leone.

Earlier this week Tullow and partners, Repsol of Spain and Anadarko of the US, announced a find that they said opened up a new oil frontier stretching 1,000km along the West African coast.

Mr Heavey, meanwhile, has watched his wealth soar. Last year he cashed in options which were worth more than £24 million and received a further £3 million in pay and additional compensation. He still retains more than six million shares in the group, worth in excess of £74 million.

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