Areas of a states’ sea territory are divided into exploration blocks to which a company can acquire the exclusive license to explore. The most favourable form of license gives a company control over a block for decades. Exploration blocks in Irish waters are held by Island Oil and Gas, Statoil, Shell, OMV, ENI, Lundin, Providence Resources, Marathon, Petroceltic, and Ramco Energy.

There are four significant fields off the west coast; Spanish Point, Dunquin, Corrib and Dooish. In addition to this there are a number of oil and gas ‘shows’, findings which have to be probed more to see if there is any major amount present.
According to industry sources considerable reserves of oil and gas may exist off the Irish coastline. The CEO of one of the major local players, Providence Resources, claims: “there is no doubt that this is the best time to be in the oil and gas industry”.

The Corrib Gas field is owned by a group headed by Shell, but also including Marathon, the operators of the Kinsale field off the south coast, and Statoil, the Norwegian semi-state oil and gas company.

The Dooish field holds both oil and gas, but the exploratory well on it was capped in July 2003, as it is apparently currently commercially unviable due to the field’s depth.
Dooish is the hands of Shell.

The feasibility of exploiting Spanish Point is being considered by Providence, the company that holds the licence to the discovery, and in February 2006 the same company entered into a deal with Exxon-Mobil (aka Esso) to develop Dunquin. Providence is to have a 16% share and Scottish company Sosina 4%. Exxon-Mobil are to cover all exploration costs. This is basically trading in licences. 45% of Providence is owned by Tony O’Reilly, who also owns much of the Irish local and national press, as well as media outlets in several other countries, and his son is the CEO of the company. His papers are markedly hostile to the Shell to Sea campaign. Dunquin contains, according to Providence Resources, 25 trillion cubic feet of natural gas and four billion barrels of oil. Exxon-Mobil is the world largest energy corporation. Providence also operate off-shore in Nigeria.

In January 2005 the Department of the Marine was offering exploration licences with the sweetener: “The infrastructure of the Corrib Field could significantly reduce the development cost of any further commercial discoveries in the vicinity.”
The 400 acres that Shell own in north-west Mayo as a site to build their refinery for Corrib gas is much much larger than needed for just that refinery, and the site itself is adjacent to state owned land for potential further expansion. Hence it is well possible that refinery after refinery will be destined for Erris, should the present proposed refinery not be stopped.

In addition in land Finavera, owns 100 per cent of the 1,630 sq km gas field in the Lough Allen basin, which crosses Sligo, Leitrim, Cavan and Fermanagh. Tom Davitt, its CEO claims "The Lough Allen natural gas field has the potential to change the energy dynamic of Ireland and the UK,".

Finally an international oil and gas company Hess LNG is to build a liquefied natural gas terminal on land owned by Shannon Development, a state body, in county Limerick, by the Shannon estuary. This is essentially storage tanks for gas refined elsewhere, which can be brought to the terminal by sea.