What is shale gas?
Shale gas is just regular natural gas - the stuff that most of us cook with and run our central heating boilers on.
Instead of being found in accumulations or 'traps' in sandstone and limestone rock formations, it's found in shale rock. Shale rock is porous (contains lots of tiny holes in which gas is found) but largely impermeable (which means fluids can't flow through it on their own without help).
The shale rock was formed sometime around 450 million years ago through a process of sediment deposition. Silt and clay particles, along with organic matter, were compacted and became buried deeper and deeper. As they were warmed in the earth, some of the organic material was transformed into oil and gas.
You can find out more about shale rock here.
Where is it found in the UK?
Shale rock, and therefore shale gas, is found in several places around the UK. These are:
The Midland Valley in Scotland
Lancashire and Yorkshire
The East Midlands
There are also deposits of shale rock in South East England, under Surrey, Sussex and Hampshire, but these tend to contain oil rather than gas.
How much shale gas is there?
In its central estimate for Scotland, BGS reports that there could be 80 tcf (trillion cubic feet) of gas locked away in the shale rock. In Northern England, the BGS central estimate is 1,329 tcf of gas.
This is known as a resource estimate or Gas Initially In Place. It won't be possible, with current technologies, to extract all of it.
But it should be possible to extract 10% of it, or around 141 tcf of the total UK resource estimate.
To put that into context, the UK currently consumes around 3 tcf of gas a year, and so it would seem there's enough shale gas to meet 100% of UK demand for over 45 years.
How is shale gas extracted?
Firstly, a vertical well is drilled from the surface all the way down to the shale rock which is found at depths of over a mile.
The drill is then turned sideways, and the well is drilled horizontally deep underground.
Once the well has been built, it's time for fracking to take place. 'Fracking' is slang for hydraulic fracturing, a process of pumping a fluid down the well and into the shale rock in order to create tiny cracks. These cracks connect the tiny pore spaces together and allow the trapped gas to escape into the well and back to the surface.
The companies that are looking for shale gas
There are currently four companies actively involved in shale gas exploration in the UK right now. They are:
INEOS Shale, part of the INEOS chemicals family, holds the largest exploration acreage but has yet to drill any wells. Cuadrilla Resources has drilled four wells in Lancashire, and partially fracked one of them. It is currently drilling a well on a new site. IGas Energy has drilled a number of wells in Cheshire and has permission to drill some new ones in the East Midlands, whilst Third Energy operates a number of producing gas wells in North Yorkshire, including a shale gas well that it drilled in 2013 and now has planning permission to frack.
The US experience
Fracking for shale gas has grown rapidly in the US since about 2005, and is now the country's dominant source of gas. It has helped to reduce energy prices for consumers, and those lower energy prices have also helped stimulate a manufacturing renaissance. Not only that but coal-to-gas switching in electricity generation has helped the US slash its power sector emissions more than any other country in the world.
It hasn't been without its problems though. In its early days, some companies did make mistakes that have unfortunately sullied fracking's reputation. The situation wasn't helped by the way mineral rights work in the US and the pressure that drill-or-drop provisions placed on companies to drill ever more wells, more and more quickly. Not only that but environmental and safety regulations weren't always good enough, and the geology is such that the shale rock is often found quite close to the groundwater aquifer. Fortunately, it's very different here in the UK - all mineral rights are owned by the Crown, not individual landowners, so there's no pressure from people leasing their mineral rights so they can collect their royalty cheques. We have very robust regulations, and the shale here is found at depths of over a mile, separated from the groundwater aquifer by layers of impermeable rock.
Take a scribble-stop tour!
From site selection to the gas you cook with, Shale Gas in Scribbles explains what's involved in under 2 minutes.