Overview

• Coal Bed Methane, or CBM, is methane gas produced from coals.
  
• CBM is “sorbed” onto the surfaces that make up the “cleats” within the coal. 
  
• Cleats are the surface planes that manifest themselves when plant material compacts.  Cleats can also be said to be the amorphous equivalent of cleavage planes found in crystalline substances.
  
• CBM molecules are “sorbed” or held in place primarily by water pressure and in part by weak covalent bonding called Van der Waals (these bonds exist when molecules that have a permanent dipole are present – e.g. water).
  
• A CBM well begins as a “fossil” water well.  As the well is pumped and the water level is depressed, the hydrostatic head covering the (sorbed) methane molecules are liberated.  Eventually water production falls off, or ceases altogether, and the volume of CBM gradually increases.
  
• Wellhead pressures are anticipated to be 0 to 4psig at the outset. 
  
• Methane purity is expected to be in the 97-98% range with 1%-2% N3 and CO2 present.  Pipeline quality gas is expected without any trace of  SO2 or H2S because the thermal window necessary for the generation of such compounds is considerably higher.
  

Further Review

British Columbia Bureau of Energy & Mines
Geological Fieldwork: A Summary of Field Activities and Current Research 2002-1

P. 319-330: Barry Ryan; Note on Desorption Results of Comox Formation Coals from the Courtenay Area, Vancouver Island, British Columbia

"There has been increasing interest in the coalbed methane (CBM) potential in the coalfields of British Columbia and some of this interest has been directed at the Comox Basin on Vancouver Island. The CBM resource of the basin has been estimated by a number of authors using published coal data. Most recently by Ryan (2001) quotes a potential resource of 0.8 tcf. These estimates are indeed estimates of the potential resource. Any estimate that is of use for an economic evaluation requires detailed information on gas contents and gas permeability of coal seams. This paper documents some new gas content data for coals from the Comox Basin."

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British Columbia Bureau of Energy & Mines
Coalbed Gas in British Columbia

Coalbed gas is formed by biochemical and physical processes during the conversion of plant material into coal. Methane constitutes the majority of gases created during the conversion process and the term 'coalbed methane' has been used by industry for gas from this source.

Coalbed gas is similar to conventional natural gas but is produced from low pressure underground coal formations rather than from underground sandstone or carbonate rock formations. It is mainly composed of methane but, like other conventional natural gases it may contain very small quantities of other paraffin series hydrocarbons such as ethane and propane. Coalbed gas has been referred to as a 'sweet gas' as it typically contains very few impurities such as hydrogen sulphide and carbon dioxide normally found in natural gas. In some cases, it can be input directly into natural gas pipelines or other gathering systems with little processing. However, in other cases, the few impurities present must be removed before being input into a gathering system.

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Produced Water Management

The Ministry of Energy and Mines contracted a private company to produce reports outlining literature available on water handling, environmental and land-use aspects of coalbed gas development and listing selective CBG references

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