What is coal seam gas ...

Excerpt from Icon Energy website

Coal Seam Methane or Coal Seam Gas

Coal Seam Gas “CSG” is a natural gas formed as a by-product during the coal formation process where organic matter was turned into coal millions of years ago.

CGG is one of the cleanest of fossil fuels and has an excellent future particularly now as we move towards placing a price on carbon. In addition to its low greenhouse gas impact, the sector may also even have some answers for another environmental problem – water shortages. Water is a by-product of CSG production and much work is being done on remediating CSG by-water to make it fit for a variety of purposes.

CSG production in Queensland has developed more rapidly than most analysts expected and already provides more than 70% of the state’s gas supplies.

In less than a decade, coal seam methane has become the dominant source of gas production in Queensland.

Unlike conventional natural gas reservoirs, where gas is trapped in the pores or void spaces or a rock such as sandstone or limestone, methane trapped in coal is adsorbed onto the coal surface (cleats and joints) or microspores and held in place by reservoir and water pressure. Hence the coal is the source and the reservoir for the methane.

CSG is an odorless gas that is used just like any other form of conventional gas to power water heaters, stoves, space heaters in both domestic and business settings and as a direct source of power for industry and as a fuel for electricity generation.

Large quantities of methane, carbon dioxide and water are generated during the coal formation process over geological time. Most of the gas and water migrates away, but some methane is retained within the coal seam. Most of this is absorbed onto the coal surface, the remainder exists as free methane in the natural fracture (cleat) system of the seams or is dissolved within the seam water. Water within the seam traps methane within the coal and has to be drawn off before the methane is extracted. As the amount of water in the seam decreases, methane production increases.

Undeveloped coal seams are generally filled with water. Methane is released when pressure on the seam is reduced, usually by removing water.

CSG production almost always involves the production of water, and most of Australia’s CSG developments are in dry regions where water is badly needed. But salts and other constituents contaminate water from coal seams, making it unsuitable for many uses.

Now, rather than simply leaving their by-water to evaporate in storage ponds, several companies are trialing reverse osmosis plants to make the water fit for a variety of uses.



Wells completed in coal deposits go through three distinct production phases.

The first phase includes the production of trace amounts of gas and in-situ water. During this initial stage, the production rates of both products are essentially constant. Generally, the water production rate is the highest rate that the well will see. Periodically, it is necessary to pump by mechanical means the water out of the wellbore as a way to produce in-situ water and gas. The methane production rate is initially characterized by a low rate, however, the methane does increase at a relatively constant rate. The first phase may last only a short time in comparison to the overall life of the well. Many first phase productions last from two (2) to six (6) months.

The wells must be de-watered so as to reduce the hydrostatic pressure on the coal face. This reduced hydrostatic pressure will allow the methane to diffuse from the coal face.

The second phase is characterized by rapid water production decline and simultaneously, the increased methane production. The water withdrawal continues for a period of time, in some wells for several months, while absorbed methane is desorbing from the microspores of the coal face and begins to flow into the fracture system that is ultimately connected to the wellbore. The desorbed methane production will begin increasing during this time.

The third phase is defined by maximum rate of the gas production and a markedly reduced water rate. Nevertheless, water must still be pumped throughout the life of the well.

The well must be periodically de-watered so as the methane gas can continue to flow and the gas is sent via a pipeline for commercial production.

The future of gas-fired power generation on the east coast will affect CSG’s prospects. Queensland power demand is expected to grow strongly over the next decade, by 3.6% per annum in the medium case and up to 6.2% in the high case according to NEMMCO (National Electricity Market Marketing Company). Emissions trading (planned from 2010) will encourage use of gas for new generation, but in competition with renewable and cleaner coal.

CSG is rapidly becoming a rapid growth sector for the investment community. International interest is increasing as pioneers companies such as Icon Energy Limited apply their skills to CSG production.

See - Icon Energy - Coal seam gas.