Coal seam gas (CSG) is the name given to any naturally occurring gas trapped in underground coal seams by water and ground pressure. The most common gas found in coal seams is methane, which is why the term Coal Bed Methane (or CBM) is used interchangeably with CSG. The gas lines the open fractures between the coal (called cleates) and the inside of the pores within the coal (the matrix).

Coal seams store both gas and water. The water, which is under pressure from the weight of overlying rock material, holds the gas in place - when the water pressure is reduced the gas is released. In the extraction (or production) process, the water pressure is reduced when a well is drilled into a coal seam and the water is gradually pumped out of the seam. This allows the gas to flow to the surface in the well.  

Arrow normally drills CSG wells no deeper than approximately 700m although gas can be produced from coal seams at greater depths if necessary.

Once a well has been drilled it becomes the only conduit for gas and water to reach the surface. The two products are separated below ground, with water being transferred to centralised collection and treatment points, and the gas being piped to processing facilities where it is dried, compressed and fed into commercial pipelines.

There are vast CSG resources spread across Queensland’s and Australia’s many coal basins. It has been commercially produced in Queensland for more than 15 years and currently supplies the fuel used to generate about 17 percent of Queensland’s electricity needs. Gas-fired power stations create less than half the greenhouse gas emissions of equivalent sized coal fired power station.