What’s the difference between natural gas, liquid natural gas, shale gas, shale oil and methane? An oil and gas glossary

Over the last few weeks, shale gas has shot into the national consciousness – resulting in more discussion on the airwaves about what, exactly, the UK’s energy future is going to look like.But it’s easy to get lost in all the technical terms. Here’s our quick oil and gas glossary to help you sort your coal bed methane from your LNG.

Natural gas:Natural gas is a major energy source around the world, accounting for21 per centof the world’s energy supply in 2010. Natural gas is an odourless, colourless gas, largely formed over millions of years underground. It’s made of a variety of compounds (see below), but methane is by far the most significant.

Natural gas is a fossil fuel, releasing greenhouse gases when burnt – but is less climate-polluting than coal, releasing abouthalf of its carbon emissions.

Typical makeup of natural gas. Source:Naturalgas.org

Unconventional gas:Unconventional natural gas is trapped in deep underground rocks that are hard to reach, such as shale rock or coal beds. Recent technological advances have made it possible to get these new sources of energy out of the ground.

Shale gas:Shale gas is extracted fromshale rockusing fracking, orhydraulic fracturing, of the rock. Shale rock is very common; theBGSestimates it makes up 35 per cent of the world’s surface rocks. It also suggests there are1,300 trillion cubic feetof shale gas in the north of England.

The application of the fracking process – which has been used in the oil industry since themid nineteenth century– to shale gas extraction has the potential to bring about a “asweeping transformation” of the energy system around the world, according to the International Energy Agency, as different countries develop the resource.

Methane:In the shale gas debate, commentators sometimes做一个区别between natural gas and methane. In fact, as the chart above demonstrates, natural gas mostlyismethane.

When it’s released directly in the atmosphere – rather than being burnt – methane is a powerful greenhouse gas. It is approximately25 times moreclimate-polluting than carbon dioxide over a 100-year timescale. Some academics are worried that methaneleaksduring the fracking process – so called fugitive emissions – will significantly increase the impact of fracking on the climate.

Liquified Natural gas (LNG):In order to feed the world’s demand for natural gas, the gas needs to be transported from where it’s produced to where it’s going to be consumed. Buttransporting gasis not that easy. LNG is created by cooling natural gas to-160ºC, creating a clear, colourless and non-toxic liquid, 600 times smaller than natural gas. Thebiggestexporter of LNG around the world isQatar, which sends it around the world in enormous tankers.

Shale oil:Fracking can be used to get not just gas out of the rock, but oil. The US-basedEnergy Information Administrationestimates that shale oil represents 10 per cent of the world’s crude oil resources. It’s not clear how much the UK has got. The British Geological Survey is working on asurveyof the shale oil resource in the south of the country. But a spokesperson tells Carbon Brief it will be “several if not many months” before the report is produced.

Coal bed methane (CBM):Methane occurs naturally underground within coal reserves. It can beextractedusing a variety of techniques. In comparison to shale gas, the amount of gas we might get from CBM seems to be fairly small – maybe around three years of UK natural gas supply, according to theBritish Geological Survey.

Underground coal gasification (UCG):UCG is an industrialprocesswhere coal is converted into gas while it’s still underground. Itinvolves钻探钻孔煤层,注入water and oxygen, and partially burning the coal underground. UCG hasnot been carried outin the UK since trials in Derbyshire in the 1950s, but recently there’s been anincreased interest in the technology. UCG has the potential to open up large new areas of coal to exploitation – a prospect that hasalarmedenvironmental campaigners.