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Further than you will ever dig lies our underground coal seams, containing a natural gas (predominantly odourless methane) which is trapped within the coal matrix by large volumes of water. 

The coal seams are the result of a carbonization process taking place over millions of years, in which trapped vegetation sinks deeper and deeper into the earth as it compresses under more and more soil. Protected from biodegration and oxidation, usually by mud or acidic water, the carbon trapped within the subsequent underground peat bogs eventually converts the dead vegetation into coal, thanks to the high pressure and temperatures present.

A coal seam gas well involves drilling down into a coal seam, passing through any aquifers used for drinking water and irrigation often found above. Depths can vary from 300 to 1000 metres. 

Multiple layers of steel casing and cement are pressure-injected to ensure the well adheres to the surrounding rock to avoid gas or fluid leakage into permeable layers, including aquifers.

Hydraulic fracking occurs when strategically placed detonators form holes deep within the well to enable a mix of water, sand, and chemicals to be pumped through at high pressure down the well and into the coal seam. Whilst most of the mix is sand and water, a low concentrate of the chemicals used are hazardous. 

The process creates a network of cracks in the coal seam. To frack or not to frack is dependent on the type of coal present and the geology of the site.  As the water flows out of cracks in the coal, the gas trapped inside is released. A mixture of water and gas flows to the surface, where they are separated and sent through an extensive above ground network of pipes for processing, where it is liquefied and stored as LNG. The large quantities of salty water, whose naturally occurring elements from underground (such as radionuclides and heavy metals) have been mixed with those from the fracking process, are now sent to an extensive network of settling and storage ponds, where some of the chemicals and heavy metals sink to the bottom. 

Remaining water is then (mostly) decontaminated through facilities such as desalination plants for reuse either on farming land or in rivers. The further waste extracted from these plants is stored in ‘waste brine’ ponds for later disposal in waste facilities.

Across Australia, LNG is exported internationally, but also retailed domestically. CSG wells are typically shallower than conventional wells. They do however require a higher density of wells than conventional gas production.