CSG Facts

Coal seam gas well site, Scotia field.

Coal seam gas (CSG) is a significant and environmentally-friendly energy resource and can be used for domestic and industrial purposes.

There are three main natural gases in widespread use throughout the world:

• Methane – used for a wide variety of purposes, including domestic heating and cooking and commercial uses such as gas-fired power stations.
• Ethane – used in the production of a wide variety of materials including plastics, paint and ethanol. Small amounts of ethane are also present in natural (domestic) gas.
• Propane and butane – also known as LPG (liquefied petroleum gas), are easily liquefied and transported. LPG is in widespread use by a variety of domestic and industrial users. LPG powers gas barbecues and converted trucks and cars.

Coal seam gas is predominantly methane gas stored within coal deposits or seams. Coal seam gas is formed as part of the same natural processes that produce coal over millions of years. It is held in coal by pressure and water. To recover CSG, coal extraction is not required.

Because coal has many fractures and a large internal surface area, it can potentially hold large volumes of gas. The amount of gas present in a coal seam depends on the thickness and depth of the seam.

At the LNG facility, CSG is reduced in temperature to -161 C, liquefied and stored at normal atmospheric pressure, providing a safe way to ship bulk supplies.

How is CSG used?

Coal seam gas can be used for the same purposes as other natural gases, including domestic heating and cooking and commercial uses.

Where is CSG found?

There are major coal seam gas resources along the east coast of Australia.

Queensland has Australia's largest onshore reserves of coal seam gas in the Bowen and Surat Basins; enough to adequately supply growing domestic demand and LNG export opportunities and ensure the long-term supply of competitively-priced gas in Australia.

Coal seam gas is an important energy resource in Queensland and production now makes up an increasing proportion of Queensland's gas supply.

Exploration for coal seam gas is also taking place at various locations throughout Australia.

Is CSG viable?

Continual improvement in technology is making gas extraction from coal seams easier to help meet the global demand for cleaner energy. Coal seam gas has the potential to produce large amounts of gas for commercial and domestic use.

The amount of gas held in coal seams may be several times greater than the current reserves of natural gas. In Australia, approximately 20% of natural gas currently being used comes from coal seam gas.

The three stages of CSG exploration and development

Coal seam gas exploration and development includes three phases:

Exploration

Wallumbilla compressor station.

The exploration phase involves drilling vertical coreholes to collect solid coal and rock cores for testing. Holes are typically between 300 millimetres and 100 millimetres in diameter and are lined with steel casing which is cemented to the side of the hole, both for safety reasons and to isolate any aquifers that are intersected.

When work is finished at a specific site, the hole is filled with cement and the area appropriately rehabilitated. An area of approximately 60 x 60 metres is usually required for drilling coreholes.

The process used for drilling is similar to that used for domestic and irrigation bores, but at a larger scale. This phase can also include seismic testing to map the subsurface geology and structure of the area.

Pilot testing

If the exploration phase indicates sufficient gas may be available, pilot testing will be carried out. This would typically comprise drilling a pattern of up to five production-sized wells, spaced at up to 1 kilometre apart. Water is pumped from the coal seams and both the water and gas are extracted and tested.

Production wells

If exploration and testing leads to a commercial operation, additional wells are drilled to extract water and gas. The distance between wells varies, depending on the project, however these are typically 500 metres to 1.5 kilometres apart and are connected by underground gas and water pipelines, which are generally constructed along fence lines and existing tracks.

The gas is treated at a central compressor station and delivered to markets by a buried high-pressure pipeline.