Coal seam gas (CSG) is produced by pumping groundwater from coal seams to release gas. In Queensland, the primary area of CSG development is the Surat Basin and the Southern Bowen Basin, although exploration is also being carried out in other parts of the state.
The Surat Basin is a sub-basin of the Great Artesian Basin (GAB), an important water resource. Some of the rock layers in the Surat Basin are permeable sandstones ('permeable' – meaning water can flow through the rock easily). Such a layer is called an 'aquifer' because a bore that is drilled into the layer can produce a usable supply of water. The water in the GAB aquifers provides bore water supplies for a range of uses and feeds GAB springs of high ecological and cultural value.
The aquifers of the GAB are separated from each other by lower permeability layers. However, there will usually be some degree of interconnectivity between aquifers through these lower permeability layers. The degree of connectivity between a coal formation and an overlying or underlying aquifer depends on how impermeable the separating layers are and the thickness of the separating layers. This connectivity means that water extraction from the coal seams can affect water levels in the adjacent aquifers.
The Queensland Government has a regulatory framework to support the responsible development of the CSG industry. This framework includes a role to assess and manage the cumulative impacts from CSG water extraction in areas of intensive development. The Office of Groundwater Impact Assessment carries out that function.