Coal Seam Gas

Coal seam gas (CSG) forms naturally with coal over millions of years as marine life and vegetation left behind in ancient sea beds becomes trapped underground in coal seams by water and ground pressure. The most common gas formed in this way is methane, otherwise known as coal bed methane (CBM). The gas is usually found lining the open fractures between coal seams that are known as, cleates. It is also found to exist inside the pores of the coal itself, it is then known as the matrix.

Coal Seam Gas is Trapped Underground by Water and Rock
Coal seams store both water and methane gas. The water is always under pressure from the weight of rock formations above the coal bed. This rock and water stops the gas from escaping but once the rock is drilled through and a well created, the water pressure is reduced by it being gradually pumped from the coal seam and the gas is released into the well.

Coal Seam Gas is Separated From Water While Still Underground
Once a coal seam gas well has been drilled it becomes the only way gas and water trapped in the cleat can reach the surface. Water is separated from the gas before it reaches the surface, the water, once separated is transferred to a collection facility where it is treated. The gas is brought to the surface where it is piped to a processing plant where it is dehydrated and compressed before being fed into commercial pipelines.

Coal Seam Gas Power Stations are Greenhouse Gas Emission Friendly
The greatest benefit gas fired power stations have over coal fired plants is that they emit less than half the amount of greenhouse gas emissions. The methane content in coal seam gas is generally between 95 and 97 percent with trace amounts of nitrogen, ethane, carbon dioxide and some others of less significance. A large amount of the gas is located between depths of 300 and 1,000 metres below the surface.

Coal Seam Gas Wells are Lined With Steel and Concrete Casings
Because coal seam gas wells are necessarily drilled through soil, rock and water to reach the coal seam, the well is lined with layers of steel and concrete casing so the gas can be separated from the water to prevent cross contamination.

Fracking Speeds up Coal Seam Gas Productivity
The method used to stimulate and speed up the flow of gas from the coal seam is known as fracking, or fraccing. This, hydraulic fracking, requires pumping sand and water into the well under high pressure. This causes the coal seam to fracture and allows more gas to flow to the surface.

Coal Seam Gas Water not Suitable for Drinking
The water released from a coal seam gas well is known as “produced” water. It is usually quite brackish, or salty and can sometimes contain heavy metals. Most gas producers store the water in holding ponds or tanks to await trucking to treatment plants. The quality of the water varies between coal seam gas fields but it is usually found to be not suitable for drinking.

Strict Licence Control Over Coal Seam Gas Development
Before a coal seam gas exploration company can sink a well to extract the gas, it must first apply to the relevant state or territory government for an exploration licence. This licence allows the company to conduct exploratory drilling and seismic surveys to ascertain the quality and quantity of gas reserves in the area covered by their licence. The company has to specifically identify sites within their licence areas where they wish to conduct their activities. However, before this can take place they must also negotiate a land access agreement with the land owner. Once this is obtained they can then apply to the relevant state or territory government to begin drilling. If the result of all this activity points to the area being viable for producing a commercial quantity of gas, the company then has to apply for a gas production licence.