Coal Seam Gas
Under construction - Michael Aouad
Description:
Coal seam gas or Coalbed methane (CBM) is a form of natural gas extracted from coal beds. In recent decades it has become an important source of energy in United States, Canada, and other countries. Australia has rich deposits where it is known as coal seam gas.
The term refers to methane adsorbed into the solid matrix of the coal. It is called 'sweet gas' because of its lack of hydrogen sulfide. The presence of this gas is well known from its occurrence in underground coal mining, where it presents a serious safety risk. Coalbed methane, often referred to as CBM, is distinct from a typical sandstone or other conventional gas reservoir, as the methane is stored within the coal by a process called adsorption. The methane is in a near-liquid state, lining the inside of pores within the coal (called the matrix). The open fractures in the coal (called the cleats) can also contain free gas or can be saturated with water.
Unlike much natural gas from conventional reservoirs, coalbed methane contains very little heavier hydrocarbons such as propane or butane, and no natural gas condensate. It often contains up to a few percent carbon dioxide. Some coal seams, such as those in certain areas of the Illawarra Coal Measures in NSW, Australia, contain little methane, with the predominant coal seam gas being carbon dioxide.
Enablers:
- Rising demand for natural gas.
- Regulation on clean energy production.
- Risk of nationalisation of traditional sources of natural gas.
- Growth of natural gas based electricity generation.
- Rising awareness of carbon emissions.
- China's demand for coal and extensive coal mines.
- Availability in nations with little or no traditional gas reserves.
- Price and tax incentives (US 1978 - 1980s)
- Development and dissemination of reservoir engineering and completion technology (1982 - 1987).
- Methane reduction in coal mining reducing accidents and greenhouse emissions.
Inhibitors:
- Environmental impact of extracting coal seam gas - mainly the disposal of water.
Paradigms:
- Brings a new view on previously uneconomical coal deposits. Previously if a coal deposit was uneconomical for mining it was left unexploited; now it is possible to extract gas from the coalbed for a much lower cost.