Water
We recognise that water is one of Australia’s most precious and important assets.
Water is used in all stages of an oil and gas project from exploration to development. Water used in natural gas operations varies in quantity and quality depending on the field and operation required. The water used also varies in quality depending on what is it used for, such as camp supplies, drilling and dust suppression.
Australia’s onshore oil and gas industry is subject to stringent regulation and scrutiny, often more than other industries with comparable or greater water consumption.
At a national level, the Australian oil and gas industry is a modest user of water. According to the ABS, our activities account for less than 0.2 per cent of water consumed by Australians annually.
Industry takes very seriously its responsibility to protect that natural asset for other users today, and for future generations.
Producing CSG water
Petroleum operations also ‘create’ or ‘produce’ water which is brought to the surface along with hydrocarbons.
In the case of coal seam gas (CSG), water is also a by-product of production, with a significant volume of water treated and then made available to farmers, local government and other users.
Coal seam gas – or CSG – is natural gas trapped in a coal seam by water pressure. Decreasing the pressure on the coals by pumping water frees the gas for production.
Treating and using CSG water
Water produced from a coal seam is mildly salty (brackish). It comes from deeper geological layers and is generally not usable for agricultural purposes without desalination treatment or blending with fresher (less saline) water.
About 80 % of the water produced during coal seam gas production is beneficially used by agriculture, industry and by reinjection in aquifers. (Gasfields Commission)
When treated and beneficially used, CSG production water can be an alternative supply to the water that is currently taken from the shallower, less saline aquifers. This in itself can assist in recharging these shallow aquifers over time.
Chinchilla farmer Ken Schmidt using treated water for irrigation.
Modelling and monitoring water supply in Queensland
Water produced from CSG is a small percentage (0.03% or 3 parts in 10,000) of Australia’s Great Artesian Basin.
Regional aquifer depressurisation models predict the impacts on water supply aquifers, and continual data capture and monitoring is used to validate and improve these predictions.
In 2012, the Queensland Government commissioned the preparation of the Surat Underground Water Impact Report. The report is updated ever 3 years and assesses the groundwater impacts from resource operations in the Surat and southern Bowen basins. It also establishes:
- strategies to manage the predicted impacts
- responsibilities for implementing various aspects of the strategies.
Gas companies have installed monitoring wells to detect any changes in aquifer pressure (using vibrating wireline piezometers) or changes in the chemistry in the aquifers underlying their permit areas. This information is delivered to the Queensland Office of Groundwater Impact Assessment (OGIA) on a six-monthly basis.
There are over 66,000 water supply bores in Queensland, 22,500 of these bores are in the Surat CMA. Less than one percent of water bores in the Surat CMA are identified as Immediately Affected Area bores. 2.5 percent of water bores in the Surat CMA are predicted to be impacted in the long term.
The main reason many of these wells are expected to be affected is because they are producing from the same coals that are to be used for gas production.
Tenement holders are required to “make good” on any bore level decline by providing landholders with alternative water supplies. This may include drilling new, deeper bores, or supplying treated water to the affected properties.
Shale gas operations and water use
Water use for hydraulic fracturing can vary depending on the geology. The Australian Council of Learned Academies estimates that between 4 and 22 megalitres per well is required for an average shale gas well, depending on the length of the horizontal section of the well.
We conserve water use as much as we can by recycling and reusing water across our wells during the drilling and fracking process. Up to 80% of the fluid used in hydraulic fracturing can be recovered. Most of this can be recycled and reused for additional hydraulic fracturing or other beneficial uses.
Water quality
For more than 100 years, Australian oil and gas operators have been operating while protecting water resources.
We also had independently verified groundwater monitoring put in place before we started our exploration work. This is ongoing.
There are many controls and safeguards in place. There are multiple layers of steel and cement separating the well from the underground layers of rock.
They are very careful to protect these aquifers and the use of any chemicals in Australian oil and gas operations is strictly regulated to minimise environmental risk, including risks to groundwater.
Regulators require monitoring and management conditions appropriate to each site during and after oil or gas production. This includes monitoring the levels and quality of local groundwater.
Geology
Australia’s oil and gas deposits are typically hundreds – or even thousands – of metres deeper that the freshwater aquifers used for domestic or agricultural purposes.
Oil and gas deposits are generally separated from freshwater aquifers by layers of impermeable rocks. These rocks form efficient natural barriers between fresh water and gas resources.
Oil and gas wells are constructed using several layers of steel casing and cement that form a protective barrier between the well and the rock. These barriers are tested by applying pressure or by electronic sound measurements – or both.