Coal seam gas

Coal seam gas is natural gas. Coal seam gas (CSG) is primarily methane – a colourless and odourless gas, found in coal deposits formed over millions of years from fallen trees and other plant matter.

Natural gas collects in underground coal seams by bonding to the surface of coal particles. The coal seams are generally filled with water and it is the pressure of the water that keeps the gas as a thin film on the surface of the coal. The technical term for this is 'adsorption'.

Natural gas in coal seams in Australia is not a new discovery. It was first identified when coal mining began in the early 1900s. With advances in technology, CSG, also known as onshore ‘unconventional’ gas has developed into a key fuel source, helping to lower our carbon emissions as we move to a low carbon future.

Where CSG is found

In Australia, coal seam gas is plentiful

Australia's major coal seam gas resources are found onshore in eastern Australia. Currently the largest known proven reserves are in Queensland's Bowen and Surat basins.

CSG has been produced from these areas since the mid 1990s. Until recently, the bulk of supply has been derived from the Bowen Basin. However, production from the Surat Basin’s Walloon Coal Measures is now growing rapidly – Australia Pacific LNG’s gas fields draws CSG from these coal measures.

Where we operate

CSG is not shale gas

Much of the current information being presented about the US natural gas industry refers to shale gas, not CSG. While both are classified as ‘unconventional’ gas resources, the geology is very different and the extraction processes also differ. With CSG comprising of mostly methane, it has far more simplified drilling, production, storage and treatment processes.

Gas extraction

To access the coal seams, a well is created by drilling a hole to the required depth. A steel casing of a slightly smaller diameter than the hole is installed and cement is then injected in the space between the casing and the borehole wall. The cement provides structural integrity and isolates natural formations in the earth from each other and from the surface.

Australia Pacific LNG, through its upstream operator Origin, use hybrid drill rigs in development drilling activities (pictured below). They are safer, more compact and drill faster with minimal disturbance, meaning there is less impact to the environment and surrounding communities.

The well development process enables some of the water contained within the seams to be pumped to the surface. This pumping reduces the groundwater pressure, allowing the gas to flow up the wells. The gas and water that comes out of the wells are separated at the surface. The gas is piped to a processing facility for distribution via pipelines to residential and industrial customers including power stations, and to the LNG facility near Gladstone. The produced water is brackish and is piped to treatment facilities.

Hydraulic fracturing helps the gas to flow

In some locations, there are limited natural pathways for water and gas to flow within the coals, especially where coals are not highly ’permeable’. In this situation, a fluid made of predominantly water and sand with a small number of chemical additives, is pumped down the well bore. The fluid is directed into an isolated section of the coal under pressure to create additional pathways (fractures) to help release and extract the gas. This is called hydraulic fracture stimulation, or hydraulic fracturing. It is a proven and accepted well completion methodology which has been used for over 60 years internationally and for over 40 years in Australia. The process is controlled and closely monitored.

Hydraulic fracturing increases well productivity and means that fewer wells are required.

We expect to hydraulically fracture approximately 30% to 40% of our wells. It enables a more effective release of gas and water from underground reservoirs. Most of our current CSG production is in high flow areas where hydraulic fracturing is not generally required.

All additives used in hydraulic fracture fluid are found in a typical household in items such as food and cleaning products.

We do not use BTEX (benzene, toluene, ethylbenzene and xylene) in our fracturing fluids. BTEX is not present in any of the chemical additives that we use.

Hydraulic Fracturing Fact Sheet

View Material Safety Data Sheets (MSDS)

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