Hydraulic fracturing in the onshore gas industry and drinking water

Hydraulic fracturing (Fraccing) is a method used to extract gas from onshore gas deposits such as: coal seams, shales and tight gas (deposits surrounded by rock/sand). Western Australia has only shale and tight gas deposits. If not done correctly, the fraccing process has the potential to contaminate surface and underground drinking water sources.

How is fraccing done?

Initially, a well is drilled into the underground gas deposit. Then, a fluid mixture containing water, chemicals and proppants (particles that hold fractures open, such as sand) is injected into the formation at high pressure to fracture it. The proppant remains in place to hold the fractures open to allow trapped gas to be accessed and extracted. 

When the fraccing is completed, a large proportion of the injected fluid mixture will return to the surface (product water) where it is stored.

What are the risks to sources of drinking water?

The risk of contaminating a drinking water reserve depends on the separation between the underground (aquifer) or the surface catchment area and the fraccing operation. In addition, the type and concentration of chemicals in stimulating fluids and the chemical by-products produced during the production of gas may impact upon drinking water reserves.

Underground water (aquifer) supplies

  • The risk of contamination within an aquifer is greater the closer to the aquifer.
  • The fluid mixture used in the fraccing process and hydrocarbons contained within the gas deposit can leach into and contaminate an aquifer through fractures within the fraccing area.
  • Cross contamination is more likely in coal seam gas operations where gas deposits are usually closer to the surface and surrounding aquifers. 
  • Cross contamination is less likely in shale and tight gas deposits which are usually located deeper underground (more than 2000 metres) and aquifers are further away.
  • All fraccing operations require a drill hole to reach the gas reserve. It is possible for drill holes to pass through aquifers. If this takes place contamination of the aquifer can occur unless the drill hole is cased along the entire depth of the aquifer. The casing must be able to withstand high pressures during the fraccing process and not deteriorate over time once the gas well is abandoned.

Surface water supplies

  • Millions of litres of water are required in a fraccing operation. After fraccing is completed, the fraccing fluid must be safely contained and disposed of on the surface.
  • During gas production water from the gas reserve may flow back to the surface, where it must be safely disposed.
  • Production water may contain many chemicals, including, hydrocarbons and heavy metals.

Who regulates fraccing in Western Australia

The Department of Mines, Industry Regulation and Safety (DMIRS) (external site) regulates hydraulic fracture stimulation in Western Australia.  Since 2018 fraccing has been prohibited within 2000 metres of gazetted Public Drinking Water Source Areas and all onshore fraccing proposals will be referred to the Environmental Protection Authority (EPA) for assessment under the Environmental Protection Act 1986.

What is Department of Health WA doing to manage the public health risk associated with hydraulic fracturing?

The EPA has agreed to refer all new proposals with the potential to impact drinking water sources to the Department of Health for review. The Department will also assess any proposals to reuse the product water to ensure the reuse is fit-for-purpose and that sufficient control measures are in place to prevent harm.

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Public Health