Coal Seam Gas (CSG), also called Coal Bed Methane, is a controversial new technique for extracting methane gas from underground. A series of wells are first drilled into the coal seam. These wells don't produce much gas until the coal seam is broken up by hydraulic fracturing (fracking). A fracturing fluid is pumped into the coal seam at high pressure to crack open the rock, this lets the gas flow to the well more easily.
Ground water contamination
Gas companies are very reluctant to say what fluids they use in the fracking process but continually state that they are quite safe. Fracturing fluids are mostly water but contain other chemicals, often including acids, solvents, surfactants, biocides, and hydrocarbons. Sand is often added to keep the fractures open and allow the gas to flow freely to the wells. Some of this toxic fracturing fluid, known as ‘flowback water‘, resurfaces but much may remain underground.
Concerns about CSG operations:
- Extracting coal seam gas (CSG) requires the removal of large volumes of generally saline "associated water" from the coal seam.
- Extracting of associated water can lower water levels in adjoining aquifers or in shallower, alluvial systems.
- In many areas, we don't fully understand how different aquifers connect to each other, nor how groundwater sources connect to water on the surface. In some places groundwater flows into to streams and rivers; in others, water from streams goes into groundwater aquifers.
- Hydraulic fracturing (fracking) causes mini-earthquakes so fluids or gases can flow. If these fractures link to fissures or faults in the rock, the fracking fluids, contaminated water or gas can move into other geological layers, contaminating the groundwater.
Salt and other contaminants
- Coal seam gas (CSG) water (also known as ‘associated', ‘produced' or ‘formation' water) is a by-product of the fracking process. Large volumes are removed from coal seams to allow gas to flow.
- associated water is often high in salt and contains many other contaminants. In Queensland, in Australia, each million litres of associated water brings up about five to eight tonnes of salt previously stored safely underground.
- associated water may also contain heavy metals, carcinogens such as benzene, toluene, ethylbenzene and xylene, and radioactive chemicals that are naturally present in coal seams. Some of these highly toxic substances become more concentrated as they move up the food chain.
The production, burning and export of CSG for energy may be little or no better for our climate future than coal.
- Coal seam gas (CSG) is a fossil fuel - a dirty energy source that adds to greenhouse pollution.
- The gas industry claims gas-fired power stations produce 70% less CO2 than existing coal-fired power stations. This figure is just the emissions released when the gas is burnt. It does not include the emissions involved in producing the gas - the drilling, fracking, compressing, pumping, liquefying and transporting the gas.
- Liquefying natural gas uses at least 20 per cent of its energy value and reduces its "cleanliness" almost 30 per cent.
- There is little monitoring of methane leakage in the oil and gas industry, but conservative estimates suggest that during the life cycle of an average coal seam gas well, 3.6 - 7.9 per cent of the available gas is leaks into the atmosphere as methane. This is between 30 per cent and 50 per cent more than the methane emissions for conventional (natural) gas extraction.
CSG may be cleaner than coal, but it is not clean, nor green.