What Is Coal Seam Gas? |
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Basically it’s methane gas with small amounts of other gases such as carbon dioxide which are removed before the methane is used as a fuel or chemical feed. The CSG is naturally kept under some pressure within cracks, pores etc in underground coal seams by the action of water molecules. To get it out, a bore is sunk through to the coal seam where, under the natural water pressure or by a pump, the gas begins to flow to the surface with the water. At the surface a simple separation operation divides the gas from water and each is piped off. The gas is pumped through pipelines at high pressure to users. The waste or ‘product’ water is presently dumped into above ground evaporation ponds. The product water is heavily saline, contaminated with metals and toxic hydrocarbons of various types from the coal seams. Releasing it untreated into the natural environment is not an option and the evaporation ponds are the cheap option approved by the Queensland Government. The product water could be pumped back underground as is done extensively in US and Canada. The CSG reserves and developing fields are, naturally enough, currently around the margins of the major deep coal basins such as Surat, Bowen, Gallilee and Moreton etc. Much of the Surat basin CSG for instance, is under high quality agricultural land which has led to some concerns from locals as to what the future holds. All mining activities come to an end sooner or later, and the prospect of thousands of hectares of evaporation ponds turning into dry, heavily contaminated metre-deep dust bowls is a nightmare waiting to happen. It has been estimated that, if the expansion of the industry goes ahead as predicted, 1000 megalitres per day of product water may be generated. As a comparison that’s enough water to service the whole of South East Queensland. There is little evidence that the risks of product water evaporation ponds are being examined. There are possible risks to health - experts have suggested as plausible the spread of disease bearing saline habitat mosquitos. Risks of chemical residue contamination of meat and crops from proposed use of product water for irrigation or stock watering, currently under investigation. Risks to the natural environment from permitted discharges to ephemeral creeks in areas of national environmental concern. To date there has been little or no publicly available evidence that there is complete compliance with issued conditions from environmental authorities as to water quality testing and use. There is also some confusion as to who owns, and is therefore responsible for, the product water when it reaches the surface.
For more information about CSG and similar developments download our briefing notes |
What is coal seam gas (CSG)? 
CSG Product Water