Coal Seam Gas
Under construction - Michael Aouad
Description:
Coal seam gas or Coalbed methane is a form of natural gas extracted from coal seams. While it is sold and used in the same way as traditional gas it's produced by non-traditional means. Over the last decades it has become an important source of natural gas for the United States and Canada. Australia also has rich deposits of coal seam gas.
It is extracted from the coal and, unlike traditional gas, contains little hydrogen sulfide. Coal seam gas is distinct from a typical conventional gas reservoir, as the gas 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 - this makes coal both a source and resevoir rock. To extract the gas the pressure in the coal bed needs to be relieved and this id done by pumping out the ground water. The large quantities of extracted water can pose an environmental hazard due to their high sodium content.
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.
- [Wikipedia - Coalbed methane]
- [US Geological Survey - Coalbed Methane - An Untapped Energy Resource and an Environmental Concern]
- [Unconventional Gas Center]
- [Enwegy Justice Network - Coal Bed Methane]
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 (e.g. China, India).
- 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.
- Changes the way China thinks about meeting energy requirements.