Stratheden

The Stratheden coal seam gas field is located 20 kilometres north west of the south east Queensland town of Dalby in the coal rich Surat Basin. It is wholly owned and operated by Arrow Energy Pty Ltd which, in turn, is owned by a 50 percent each joint venture agreement between Shell and PetroChina. The Stratheden coal seam gas field produced its first commercial quantity of coal seam gas (CSG) in July 2009.

The Stratheden Coal Seam Gas Field is owned and Operated by Arrow Energy
The Stratheden CSG field, along with the Daandine CSG field, which is also owned and operated by Arrow Energy, supplies coal seam gas to the Braemar 2 Power Station under a 12 year contract. Both gas fields are also an important part of the giant Surat Gas Project that is being developed to provide CSG to the fast growing domestic and export market through the planned Arrow LNG Plant on Curtis Island at Gladstone.

Stratheden Coal Seam Gas Field is Part of the Surat Gas Project
The Surat Gas Project is planning to expand current producing coal seam gas fields at Stratheden, Kogan North, Daandine and Tipton West as well as develop other wells from Dalby to Wandoen and south to Goodiwindi and Millmerran, areas in which Arrow Energy already hold environmentally approved exploration permits as well as petroleum tenure. The Stratheden coal seam gas field will therefore become part of Arrow Energy's largest ever gas exploration, development and production program in the Surat Basin. The project is to be developed by stages, its rate and extent of development will depend on the results of an ongoing exploration program as well as the level of demand for LNG in both the domestic and export markets.

Stratheden Coal Seam Gas is Naturally Forming
Coal seam gas is a naturally occurring gas that has become trapped in underground coal seams by ground pressure and water. It is mostly comprised of methane, the reason many people refer to it as being coal bed methane, or CBM, The reference CBM and CSG meaning the same thing. The gas lines the open fractures, or cleates, that exist between the coal seams. It also exists inside the pores within the coal bed itself, otherwise known as the matrix.

It is the water, that is under pressure because of the weight of the overlying rock, that holds the gas in place. This water pressure has to be reduced before the gas can be released. The Stratheden coal seam gas field, like most other gas fields in the Surat Basin, releases the entrapped gas when a well is drilled into the coal seam to allow the water to be gradually pumped from the seam. This process allows the gas to flow to the surface in the well.

Most Arrow Energy coal seam gas wells are drilled no deeper than 700 metres, although the depth can be greater when the need arises. Once the well has been drilled it is the only means by which the gas and the water can be brought to the surface, although the two are separated while still underground with the water taken to a centralised treatment area and the gas piped to a plant where it is dried and compressed before it is fed into commercial pipelines.

Stratheden Coal Seam Gas Helps Lower Greenhouse Gas Emissions
The Braemar 2 Power Station, that uses Stratheden coal seam gas to produce electricity, does so by emitting less than half of the greenhouse gas emissions than would otherwise be produced, should it have used coal. Coal seam gas has been commercially produced in Queensland for over 15
years and it is currently supplying fuel to generate 17 percent of the state's electricity requirements.
†