What Is Coal Seam Gas?

By Author: Finn Xavier
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Coal seam gas in Australia is a form of natural gas (methane) found in coal seams, rather than in the sandstone reservoirs that hold conventional natural gas. As an end-use product, it is the same as conventional natural gas and is used to generate electricity and to power natural gas appliances such as heaters and stoves. Methane is a natural by-product of coal formation and is held within the coal seam by water pressure. When this water is removed the gas is released. Coal seam gas Australia is used for fuelling natural gas appliances and in the generation of electricity. It has an overall lower impact on climate change than coal when used as an energy source.Coal forms over millions of years, storing large quantities of a methane-rich gas and coal seam gas (CSG) in Australia. Other names for gas extracted from underground coal deposits are:

Coal bed methane (CBM)
Coalbed methane
“Unconventional gas”
“Sweet gas”

Unlike coal, the coal seam gas in Australia lacks hydrogen sulphide. The methane lines the inside pores of the coal and is also found in the cleats (open fractures ...
... in the coal) and seams. The gas is held in place by water pressure.

Gas is extracted by drilling a steel-encased hole into the coal seam. Natural gas is released from the coal as the water is pumped out. The water is removed from the gas allowing the gas to be piped to a compressor station for injection into natural gas pipelines. The water is either sent to evaporation ponds, released into streams, re-injected into isolated formations or used for irrigation.

Coal seam gas exploration in Australia involves geological studies that provide scientific data used to assess whether coal seam gas is available in commercial quantities. Seismic surveys are used to produce a detailed image of the geology beneath the earth's surface to determine the size and location of coal seams. Seismic surveys use sound waves produced using specialized truck-mounted equipment and read by recording devices at the surface. If the survey is successful these may be followed up by drilling to recover core samples or to test gas flows. Exploration wells are also used to assess the likely impact of local coal seam gas production on aquifers to measure how much water is actually pumped from wells before the gas is produced. Once this is done the regulator can make an informed decision on to the likely impact of any proposal for full-scale production.

Commercial production of coal seam gas in Australia requires the drilling and construction of a number of wells. These activities are tightly regulated by the Government. Wells are typically drilled at a spacing of between 200 and 1000 meters and each well occupies a space of about 10 by 10 meters. Steel pipes are installed in the well and the gap between the casing and borehole wall is filled with cement that ensures that there is no cross-contamination between the coal seam and any overlying aquifers. Coal seam gas has become a very important source of energy, especially within Australia where it supplies over 60% of the total gas market in Queensland. Gas is used to supply some of our electricity needs like running our lights, appliances and hot water.