In reply to Postmanpat:
It's clear that shale gas brought down the price of energy in the USA, which was good for their economy, but it's not at all obvious the same would happen in the UK even if shale gas was exploited on a big enough scale, which I don't think it will be any time soon, for reasons below. The USA was disconnected from world gas markets and so following the rapid expansion of shale gas there was a glut which made US gas prices diverge from the rest of the world. There's been political resistance to building the gas liquification plants that would allow the US to export the gas and thus get higher prices for it. The UK, in contrast, is very well connected to world gas markets via long distance pipelines and imports of LNG, so this won't happen here.
I'm quite prepared to believe that there's a lot of shale gas in the UK, and even that it won't be that risky if done properly (though I think there are still questions to answer about methane leakage, which is important given what a powerful greenhouse gas methane is). But I don't believe that it will be extracted at any scale - certainly not at any scale that would make a real difference to our energy economy - in the near future.
The key difference between shale gas and conventional gas is, as a few people have mentioned above, the very rapid decay in flow rates, on time scales of only a year or two. It's not a question of drilling a well, and then inconspicuously piping the gas away for the next ten or twenty years, as happens with conventional gas. you've got to keep drilling new wells to replace the old ones, often at densities much more than one per square kilometer. This research note is instructive on the economic implications of this:
http://about.bnef.com/press-releases/uk-shale-gas-no-get-out-of-jail-free-c...
It's instructive to take a look on Google Earth at intensively developed shale gas areas in the USA, like round Fort Worth, TX, where the oblong patchs of drilling pads are very obvious. Now try to imagine that density of industrialisation - a thousand new wells per year, according to the estimate cited above - in Cheshire, Sussex, the Costwolds, E. Yorkshire, pausing only to compare a map of shale prospects with a map of Conservative rural constituencies. It's not going to happen. Apart from anything else, the drillers are US/international, they don't need to come here to put themselves through those planning hassle and expense when there are plenty of other countries with shale/unconventional gas in less controversial places.
I'm sure there are people in government who know all this (or they should, if they listened to anyone other than Lord Browne). So why are they hyping shale gas up so much at the moment? In the past I'd have wondered, as so often with this government, whether it was stupidity or dishonesty (or possibly both). But now I've come to realise that what we've got is actually the first completely post-modern government, which sees no need to make any connection between what it says and reality, as long as it has the appearance of doing something. So lots of talk about shale gas now gives them the appearance of having an energy policy. Unfortunately real life, in the form of the consequences of the shambles their energy policy is in reality, will catch up with us all before long.