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6 May 2019
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23 February 2015
Coal seam gas (CSG) is simply natural gas, which consists mainly of methane. It’s used every day to generate electricity, run home appliances, and fuel businesses and industries. In fact, CSG provides 90% of Queensland’s gas needs.
CSG is a a term used to describe the gas found in coal seams (areas of underground coal). These coal seams can be anywhere from 200 metres to 1,000 metres below the earth’s surface. The natural gas bonds to the surface of the coal as a thin film, and underground water pressure holds it in place.
The CSG we use today started forming millions of years ago as a by-product of decaying organic plant matter. Layers of sand and soil compressed the matter and over millions of years, this compression, combined with the earth’s heat, converted it into natural gas.
Extracting and processing CSG is a multi-step process:
CSG wells are about the size of a dinner plate. They are drilled into the ground until they reach the coal seams, and the surrounding area is lined with steel casing and a cement barrier to protect it.
First, some water is extracted from the well. This reduces the pressure in the underground coal seam and allows the gas to flow into the well and to the surface.
When in operation, the surface area of a fenced CSG well is generally around half the size of a netball court, and land uses, such as farming and grazing, outside the fenced area can continue.
Once the gas and water reach the surface, they are separated and flow along underground pipelines to nearby processing facilities. Water is sent to a treatment facility and gas is sent to a processing plant.
Once the gas arrives at the processing plant, any remaining water is removed and the gas is compressed (put under pressure so it can flow) for distribution.
The gas is transported along pipelines to either Australian residential and industrial customers or it’s sent to a facility to be turned into a liquid (liquefied natural gas, LNG), which makes it easier to export overseas.
LNG is liquefied natural gas, which is gas in liquid form. To create LNG, the CSG is cooled under pressure to a temperature of minus 161˚C. During the cooling process, any existing traces of carbon dioxide, water and other impurities are removed. Liquefaction shrinks CSG to 1/600th of its size making it easier to transport.2
The LNG is stored in tanks, before it is exported in purpose-built ships for export overseas. When it arrives, the LNG is turned back into gas and used to fuel power stations, homes, businesses or for electricity generation.
Once a CSG well is no longer being used, it is decommissioned (plugged with cement) and the area is returned to its natural environment.