Petroleum engineers have been fracking for over a hundred years. They've known for ages that fissures in source rocks improve the flow of oil into reservoirs and so increase recoverable reserves. So already in the 1860s engineers were packing nitroglicerine underground and detonating it. But it was the first oil shock that made the US government and oil industry seriously interested. Research in the 1980s produced the hydraulic fracking of today, with Texan gas company Mitchell Energy being the first to come up with economically viable "slickwater fracking".

The oil and gas companies from the Southern USA (especially Texas, Florida and Oklahoma) who pioneered the technique (like Mitchell Energy) and bought up drilling rights in areas previously considered of no value.

Landowners on the big gas bearing shale formations in the USA - the Marcellus Shale, mostly in Pennsylvania, and the Barnett Shale, further south

The oil majors who got into the game late and overpaid for US acquisitions

Companies with competing, but more costly, energy assets, like deepwater offshore oil and gas and coal mines

Russia, whose Gazprom has contributed massively to state wealth, if and when the shale revolution hits Europe. Same will go for Algeria, that has profited handsomely from supplying mainland Europe in gas. Countries with big conventional gas reserves a long way away will also feel a new pinch. Western Australia, Central Asia, Iran and Qatar will all be hit.

Map

All over the world, including places like China and Western Europe that have traditionally thought of themselves as being energy poor

The UK has two major shale formations - one in the North West, in Lancashire and under the Irish Sea - the other in the South, stretching from the South Downs to Dorset and Somerset. Production in the economically depressed North West is greeted with more enthusiasm than in the rolling countryside of the booming and over-crowded South of the country.

2015, according the Chancellor's autumn statement this year.

Household bills in the UK may not fall that much - certainly they are unlikely to fall as have done wholesale prices in the US. The government will set royalty rates at the level the market will bear, and that'll be close to current levels. (In the US, the owner of the land owns the resources underground. No single owner has the monopoly power to set prices, so they tend to be lower.) There is also a battle raging at the heart of government between the Treasury and the Department of Energy and Climate Change (DECC). DECC wants 80% reductions in greenhouse gas emissions by 2050, so wants energy prices kept high. The Treasury is more interested in government finances and growth. But whoever wins, continuing high gas prices are likely to be the result. There might be some pass-through of benefits to large industrial users, but don't expect household bills to fall.

Everyone agrees that fracking needs careful engineering. Methane leaks need to be stopped by building sound concrete casing around the bore-holes. This will also stop groundwater contamination. The quantity of nasty chemicals used to keep the fractures open (acids, emulsifiers) could be reduced significantly. Some engineers have even suggested that air could be used instead of water to fracture the shale.

Cheap domestic energy will create an investment boom that could kick-start the economy. The existence of cheap high-quality energy will make heavy industry and manufacturing investment more attractive which will have the much-vaunted longer term effect of rebalancing the UK's economy away from financial services. Already in the US there is a move to "on-shore" production of steel and chemicals because of the availability of cheap energy.

In the UK, the Treasury could make a killing from Shale gas. All underground resources are owned by the state which has proved adept in the North Sea, for example, at setting royalties - the money paid by the operator to the government - just at the point at which it just makes sense for oil companies to keep exploring and producing. The government will do just the same with onshore shale operations. The North Sea oil bonanza allowed the Conservative government of the 1980s to keep taxes low, to beat the coal mining unions and to balance the books. What statesman wouldn't want a repeat of that?

Greens used to get some comfort from the idea that "peak oil" was upon us. Fossil fuels would run out, so even if the mainstream wasn't going to take renewables seriously for good environmental reasons, the coming shortage would make everyone pay attention. But shale gas changes all that. We won't be forced into really green energy - solar, wind, geo-thermal - any more.

There's not much hope of seriously denting our greenhouse gas emissions until a cheap clean alternative fuel is found argue some moderate, realist greens. Shale gas is better than oil and coal for making electricity and it gives us the 30 year window to develop the technologies we need - better solar, wind, nuclear (maybe even fusion) and efficient bio-fuels.

Basic Geology

Basic Engineering

Lots more cheap energy

There are environmental worries

it makes earthqukes