Water management

Typical Section of the Walloon Coal Measures

The Great Artesian Basin (GAB) comprises many different geological layers. Some of the layers such as sandstone are porous and allow water to flow through them. These are known as aquifers and are the layers typically accessed by farmers and others for groundwater supply. Below the main aquifers used for water bores are denser geographical layers that are much less permeable and do not allow water to pass through them freely. These are called aquitards. The coal seams from which CSG is produced are generally much deeper than the commonly used GAB aquifers and are also often surrounded by thick aquitards.

Water produced by the CSG to LNG industry in Queensland over the next forty years (the time to complete the current CSG to LNG projects) will be about half the amount taken by other users in the same geographical area over the same time. Compared to the annual recharge of the Great Artesian Basin, the amount of water extracted by the CSG industry is small.

Coal seam water is generally too salty for use

The water within coal seams is generally too salty or brackish to be used for agricultural or other purposes. Graziers, farmers and others mainly take water from the sandstone aquifers that are above the coal measures. However, in some cases bores take water from sandstone aquifers below the coal seams or from the coal seams themselves.

Generally the process of extracting CSG does not take water from the GAB that otherwise might be used by landowners. The diagram above shows where the coal seams are typically positioned relative to aquifers usually used for agriculture. In Australia Pacific LNG’s operating areas, they are typically separated from the shallow aquifers by approximately 100m to 250m (equivalent to a 25 to 65 story building) of low-permeability rock.

The brackish water extracted from the coal seams is treated in reverse osmosis desalination plants to drinking water standard and then released to local waterways and for use in agriculture. Origin is currently trialling broad acre cropping and a 300 hectare Pongamia tree bio-fuel plantation, both utilising treated CSG water. The treated water extracted from the coal seams is also used at our construction and operational facilities in the gas fields.

We seek beneficial uses for CSG water

Queensland Government policy on disposal of water produced from CSG extraction is in order of preference: re-injection into suitable aquifers, beneficial use and discharge into waterways. Australia Pacific LNG is exploring all three of the Government’s preferred options. If feasible, aquifer injection is likely to play an important role in Australia Pacific LNG’s water management strategy, and although it will not provide water directly to farmers, it will increase the reliability of groundwater supplies. Beneficial use by providing treated CSG water to existing users will provide more direct benefits to overall water use in the GAB.

We are exploring commercial use of the salt

The amount of salt produced across the four proposed CSG to LNG projects in Queensland is estimated to be of the order of 10 million tonnes over the life of the projects [Source: Senate Inquiry report and company statements]. This is a similar amount of salt that is currently brought to the surface in groundwater used for agriculture and other purposes in Queensland every year.

Other users spread the salt brought up in bore water directly onto farms or into waterways, via its use to irrigate crops and feed livestock. We treat CSG water to Australian drinking water standards and make it available for other uses, including for use on farms.

The salt that remains after water treatment forms part of a residual solution known as brine. The brine is stored in specially built ponds that are subject to strict construction and lining requirements to prevent it from entering the surrounding environment. Over time the water from the brine evaporates, leaving concentrated salts to be disposed of. Origin and other CSG to LNG companies are exploring options and undertaking trials to investigate commercial use of the salt.

It is estimated that the Great Artesian Basin (GAB) has an enormous total storage capacity of 65,000 million mega litres. Each year it is naturally recharged with 920,000 mega litres. [Source: Great Artesian Basin Coordinating Committee]

Water extraction is relatively small

At their peak, all the proposed CSG to LNG operations combined, will take approximately 0.0002% of the total water that is stored in the GAB. Aquifer injection has the potential to return a significant proportion of this water directly back to the basin’s aquifers. Any treated CSG water provided to existing users is likely to also directly reduce existing usage of GAB water.

Current modelling estimates indicate that the combined average water extracted from the Surat Basin section of the GAB for the proposed Queensland CSG to LNG industry is 75,000 mega litres per year. This is much less than the estimated 620,000 mega litres extracted from the GAB annually by other users. It is also less than the estimated average amount of groundwater taken for agriculture and other purposes across the Great Artesian Basin.

There are potential impacts on some local water bores

Pastoral and industrial use of the GAB over the past century has resulted in aquifer pressure drops of several tens of metres in heavily developed areas [Source: Great Artesian Basin Coordinating Committee].

Impact on water bores is low

CSG related water extraction is not expected to significantly impact on landowner, grazier and farmers’ groundwater supplies, as they are typically separated from the coal seams by hundreds of metres of low permeability rock. However, in some cases CSG activity could affect bore water levels. We are required under Government legislation to monitor such impacts and are legally required to rectify or “make good” in advance, on the basis of water modelling projections, any impact on landowners’ water supplies and their operations.

The Queensland Water Act 2000 was recently amended to introduce a new regulatory framework to manage the cumulative impacts on water supply bores and springs from the CSG industry. It also establishes the independent role of the Queensland Water Commission to oversee the monitoring of cumulative impacts on groundwater.

These Government regulations are reinforced by strict conditions that have been imposed by the Federal and Queensland Government when approving the CSG Projects. The Queensland Water Commission has full access to the water quality and quantity data from the hundreds of baseline tests we have done on existing bores and from the more than 60 dedicated water monitoring bores that we have established in the Surat Basin.

The huge quantities of new and ongoing information about water levels and water quality that will be made available to the public in this way by Australia Pacific LNG and the other CSG to LNG proponents will help to make the Surat Basin one of the best understood underground water systems anywhere in the world.

There is a long history in the Surat Basin of gas occurring naturally in water bores. Historical state government records report the presence of natural gas in many bores and in all commonly used GAB aquifers. In fact Australia’s first natural gas discovery was made whilst drilling for water in 1900 at Hospital Hill in Roma.

In fact Australia’s first natural gas discovery was made whilst drilling for water in 1900 at Hospital Hill in Roma.

Gas is still naturally occurring in many bores today.

The presence of gas in water bores is particularly common in areas such as Hopelands, where the Walloon Coal Measures are shallow and are used for stock water supply. In some cases, as recently shown on current affairs television programs, it is possible to light the gas present in a bore creating the spectacle of a ‘flaming bore’. This is not related to CSG activity.