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High Levels of Methane Around Coal Seam Gas Fields

Southern Cross University academics have reported unusually high levels of methane around coal seam gas fields in northern NSW and the Tara gas fields in southern Queensland.

Source: AusSMC

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“A team from Southern Cross University recently reported high concentrations of methane in the Tara basin CSG field. I have seen these data and the methods that underlie them. The data themselves are very solid; this is state-of-the-art equipment and contamination is very unlikely, especially given the large spikes they observed.

Concentrations, however, are not what we're really interested in. One can get high concentrations near even small leaks, especially in an enclosed space. We are really interested in emissions.

Here the task becomes harder since we need to know how fast an emission dilutes into the atmosphere then back-calculate the emission from the measured concentration...To do it we run a computer model of the atmosphere like those that calculate pollution in cities. The model accounts for the movement of pollutants by the winds and the problem of trapping pollutants under inversion layers.

The Tara basin measurements are a tough challenge since they were taken at night and under calm conditions. These conditions usually produce high concentrations for a given emission.

Our team at the University of Melbourne hasn't modelled the Tara measurements yet but we have modelled another gas field under somewhat similar conditions and made a simple extrapolation. If we believe the extrapolation, the Tara emissions are several thousand tonnes...

The full text of this article can be purchased from Informit.