Code of Practice for coal seam gas well head emissions detection ...

stringent monitoring regime has been put in place in order to meet community expectations and
ensure community confidence in the leak monitoring and gas field safety regime.
A standard leak measuring methodology has been adopted for the industry under this Code of
Practice. This methodology requires gas/air content to be measured at 150mm from source, with
all leaks above 10% LFL being reportable. This exceeds the current standard level of 20% LFL at
200mm distance used by some major operators in gas processing plants which have significant
gas infrastructure often in confined spaces.
General CSG safety
CSG is a safe energy source that is a by-product of the natural conversion of plant material to coal.
CSG consists mostly of methane which, like other forms of natural gas, can be used as a fuel in
heaters, stoves and hot water systems in homes and businesses. Methane is non-toxic and is only
flammable when the gas concentration is between 5% and 15% per cent of the total gas/air
mixture. CSG is lighter than air, meaning it will rise naturally and quickly dilute and dissipate into
the air in an outdoor environment. In addition to its application in domestic and business
environments, natural gas is safely used in many other areas including transport fuels and as
feedstock or fuel for industrial plants.
CSG well site facilities are constructed to Australian or International Standards where applicable.
These facilities are pressure tested prior to commissioning to verify the integrity of the facilities and
the CSG operators conduct routine monitoring to ensure ongoing safe operation of the facilities.
For CSG to reach a flammable state, it must first form a concentration level of between 5% and
15% of gas in air. A typical potential gas leak at a well head site is likely to emanate from a gas
flange or screwed joint. This type of leak is generally insufficient to support combustion.
The lower explosive limit (LEL) or lower flammable limit (LFL) of a combustible gas describes the
smallest amount of gas that supports a self-propagating flame when mixed with air (or oxygen) and
ignited. In gas-detection systems, the amount of gas present is specified as a percentage (%) LFL.
Zero percent (0%) LFL denotes an atmosphere that is free from a combustible gas. One hundred
percent (100%) LFL denotes an atmosphere in which the gas concentration has reached its lower
flammable limit. The relationship between percentage LFL and percent by volume differs from gas
to gas (for example liquid petroleum gas (LPG) has a different LFL to CSG).
This Code of Practice describes the actions that CSG operators must undertake for leaks that have
measured gas concentrations as low as 10% LFL, which is an order of magnitude less than a
flammable concentration. A 10% LFL is a very conservative standard and leaks of lower
concentration of methane in an open air rural gas field environment are not regarded as a
significant risk.
Appendix 1 provides a comparison of the properties of CSG compared with LPG.
Definitions
Definitions for terms used in this Code of Practice are outlined in Appendix 2.
Code of Practice for CSG well head emissions, detection and reporting - Version 2 June 2011 6