So, here's the drill...
Why are we talking about fracking?
Two companies, Tamboran Resources (Australia) and Enegi Oil (Canada), have options to secure exploration licences allowing them to look for shale gas underneath parts of Clare, Leitrim, Sligo and Fermanagh. While they cannot drill any wells in the Republic for at least another two years, Tamboran expects to carry out more detailed studies early next year in Fermanagh.
Tamboran has a licence to explore 986 sq km of the Northwest Carboniferous Basin, while Enegi Oil has a licence for 495 sq km in the Clare Basin.
What is shale gas?
It is found in deposits of shale; coal bed methane and tight gas, or gas trapped underground in impermeable rock. Shale gas was formed millions of years ago.
How is it brought to the surface?
This is where the controversy arises. The method used is called hydraulic fracturing, or fracking. A well is drilled and large volumes of water mixed with sand and chemicals are injected underground at high pressure to create cracks in rocks, which remain open.
This frees the gas, allowing it to flow to the surface where it is captured and processed.
It sounds complicated.
It's not really. Similar technologies have been used in the US for the past 40 years. Production of Shale gas in the US ramped up from 2005 onwards, and represents more than 20pc of all gas production.
Is there much gas out there?
The companies believe that more than six trillion cubic feet (tcf) of gas could be extracted. Tamboran says more than 2.2tcf could be taken from a site straddling Fermanagh and Leitrim, while Enegi says there could be between 1.49tcf and 3.86tcf under Clare. By way of comparison, the Corrib Gas field – which could produce for 20 years, has about 1tcf.
Is shale gas unique to Ireland?
No. The International Energy Agency (IEA) says there's about 190 trillion cubic metres of proven gas reserves worldwide, or about 60 years' current annual production. But recoverable resources, or volumes that will be discovered or technology developed to produce them, are much larger, perhaps as much as 400 tcm.
Has it ever been done before here?
There has never been full-scale production, but exploration wells have been fracked as far back as 1981 (Cavan) and in 2002 in Fermanagh and Leitrim.
What happens the gas after it's extracted?
It's processed and either shipped by road or fed by pipeline into the national grid.
So what does this all mean?
It means that if enough shale gas is found, and it makes economic sense to bring it to the surface, fracking could become a reality in Ireland.
What are the pitfalls?
The long-term implications of fracking are not known. The chemical mix used by each company is different, and could contaminate groundwater.
There's also a question as to whether there's enough water to facilitate the process with between 90,000 and 13.5 million litres of water required per well.
What are the upsides?
Oil and gas companies say the gas will help reduce fuel bills and provide security of supply. We currently import more than 90pc of our fossil fuels at a cost of €6bn a year. They also claim that hundreds of jobs will be created and tax revenues paid to government once production begins.
How much would my bills be reduced by?
Very hard to say. In Europe gas is traded internationally. Even if the full potential of Clare and the north-west is exploited, it doesn't mean all the gas would flow to Irish customers. It may be cheaper to get gas from abroad.
So what's the Government doing?
It has asked the Environmental Protection Agency to carry out a study setting out the concerns, and how they can be addressed. That will take two years to complete.
Should I be concerned?
Yes. While there are economic benefits, there's risks too. There's also the question of whether drilling in areas of natural beauty is worth it.
Sources : International Energy Agency; investor presentations Tamboran/Enegi Oil; Department of Communications, Marine and Natural Resources; European Parliament 'Impacts of shale gas and shale oil extraction on the environment and human health'; 'Unburnable Carbon 2013: Wasted capital and stranded assets' from the Grantham Institute of Climate Change and the Environment, LSE; 'Hydraulic Fracturing or Fracking: A short summary of current knowledge and potential environmental impacts', University of Aberdeen on behalf of the EPA.