On Friday, Tullow Oil, founded by chief executive Aidan Heavey, said it had discovered new gas reserves in the North Sea, its principal asset base outside Africa. It is the company's seventh gas discovery in the North Sea area since 2001.

Heavey said the find has "potentially significant implications for future exploration in the region".

Tullow stock has risen 20% this year and the company is now valued at £2.1bn ( 3.07bn).

Heavey owns six million shares in the company, which are now worth £19.4m ( 28.4m).

Also on Friday, Burren Energy, founded by chief executive Finian O'Sullivan, said it had found fresh oil reserves in Congo.

"This result, one of the best obtained on the western edge of the structure, raises the hope of a new drilling platform in this area to drill productive wells to compensate for the natural depletion of the reservoir, " Etablissements Maurel & Prom, operator of the M'Boundi field, said in a statement.

Burren Energy shares rose as much as 8.9% on the news.

They closed at £7.59, valuing the company at £1.1bn ( 1.6bn) and O'Sullivan's stake in the firm at £40.3m ( 59m). O'Sullivan floated the firm in 2003 at £1.25 per share.

The rise in Heavey's and O'Sullivan's personal wealth dwarfs that of Dublin-born David O'Reilly, chairman and chief executive of Chevron, the second largest oil company in the US. He owns just over 90,000 shares in what is the world's 11th-largest company by revenue. They are worth approximately $5.2m ( 4.11m).

A number of Irish minnows have also seen their market capitalisations rise on the back of the scramble for oil. Island Oil & Gas, founded by chief executive Paul Griffiths, floated in London in late 2004. Its stock has risen over 22% in the year to date, valuing the exploration firm at almost £63m ( 92m). Griffiths' stake in the company is now worth almost 4.3m.

Meanwhile, UK-based Crescent Diagnostics has snagged 800,000 in funding from Seroba BioVentures, the Dublin venture capital outfit, as well as some private investors.

Founded in 2002, Crescent Diagnostics is developing a Bone Quality Test (BQT), discovered by two University of Limerick academics, Mark Towler and Declan Lyons, at the Materials and Surface Science Institute.

The BQT assesses osteoporosis fracture risk and drug response by examining the fingernail. The current method involves exposing the patient to expensive scans. In preliminary studies, Crescent showed that its BQT is a better predictor of fracture risk.

As part of the latest financing, Alan O'Connell, a partner with Seroba, will join Crescent's board of directors.