Enhanced coal bed methane recovery
Enhanced coal bed methane recovery (ECBM) is a technique which increases the yield of methane (CH4) in otherwise unworkable coal seams.
Principle of enhanced coal bed methane recovery in a layer of bituminous coal
During the formation of coal, the methane produced is stored in the coal by adsorption or in fractures in the seam. The standard technique for extracting this gas is to reduce the pressure of the geological reservoir by pumping.
However, the yield can be increased by the use of enhanced recovery techniques. This involves injecting carbon dioxide into the coal seam. The adsorptivity of carbon dioxide on coal is greater than that of methane causing the latter to be desorbed making it possible to extract it.
Advantages and limits of this technique
This technique has the added advantage of storing CO2 in the coal seam, making it a candidate in solutions for the capture and sequestration of CO2.
Two obstacles stand in the way of this technique being generalised: its profitability and the limited understanding of the processes at work in these coal seams.
The different techniques envisaged for geological storing of CO2. At 4 is enhanced recovery in which methane is exchanged for CO2 in coal seams. © Giec 2005
Enhanced coal bed methane recovery - 1 Photo