This project, led by the University of Queensland’s Centre for Natural Gas, aims to develop best practice methodology for gas sampling from water bores in order to differentiate and measure naturally occurring subsurface gases.

Naturally occurring methane is common in groundwater systems in the Surat Basin. There are multiple geological and biological sources and processes which give rise to it. Against this backdrop, the State also licences companies to beneficially develop its gas resources and requires that numerous impacts are monitored. Assessing the additional or incremental impacts of unconventional gas development on the level of gas in aquifers and groundwater bores is therefore an extremely complex and non-trivial scientific endeavour.

The project aims to improve industry and regulator ability to manage key areas of environmental and stakeholder concern surrounding the potential for unconventional gas development to increase the level of gas in groundwater bores. In doing so, the project aims to identify efficient and effective approaches to demonstrate where cumulative impacts are and are not affecting water bores.

The methane that is extracted by the coal seam gas industry formed in the subsurface over millions of years. Some gas has naturally migrated through the subsurface over geological time — the volume of methane currently in the system is only a fraction of what initially developed. Consequently, water bores in gas rich areas, like the Surat Basin, can contain minimal through to significant levels of methane purely as a result of natural processes and the pumping of groundwater. There is also the potential for unconventional gas production to increase the flow of gas through the subsurface into nearby water bores. High gas levels can interfere water bore pumping, and it is important to identify the source of the gas (natural flow or fugitive emission) when making decisions about the management of the affected bores.

This project aims to develop technology that can be used to identify the sources and transport pathways of methane. This involves devising a ‘fingerprinting’ methodology for characterising methane sources that uses information on gas chemistry, isotope chemistry, as well as knowledge of key processes that occur during migration (fractionation, oxidation, biological activity etc.).

This methodology will be matched with the development of a recommended industry sampling procedure and standard analysis techniques to quantify desorbed methane from different sources that is present in water bores and coal seam gas (CSG) wells.

Project objectives include:

1. Developing a method to assess shallow gas migration potential via different subsurface pathways and processes.
2. Developing a method of chemical fingerprinting to enable gas source identification.
3. Developing a cost effect gas sampling technique to generate repeatable, robust results.