Research from CSIRO's Climate Science Centre and the University of Melbourne, published in the journal Geoscientific Model Development, records for the first time the past and current changes in all 43 greenhouse gases released into the atmosphere as a result of human activities and industrial processes in Australia.
The Commonwealth-funded CSIRO Energy to study methane emissions from well completions as there was no public data on emissions from CSG well completions specific to Australian operations.
Report co-author, CSIRO's Dr Paul Fraser, said it was encouraging to see the decline in some greenhouse gases, such as CFC-12 and CFC-11, in response to the Montreal Protocol.
CSIRO principal research scientist and report co-author Dr David Etheridge said that providing long-term spatially and seasonally precise measurements of greenhouse gases for input into climate models would allow more robust future climate estimates.
More interesting to the upstream industry, however, was the fact that the report, prepared for the Department of the Environment and Energy, measured methane emissions at nine well completions and one well workover at two CSG sites in Queensland.
While the sample size is small, the Australian Petroleum Production and Exploration Association said those measurements obtained by the CSIRO provided further support for the veracity of estimating methodologies used under the National Greenhouse and Energy Reporting Scheme.
While APPEA CEO Dr Malcolm Roberts said the research would help address concerns about fugitive emissions from CSG production, activist group Lock the Gate's Naomi Hogan noted with concern the report's revelation that the single CSG workover measured caused "more than 21 tonnes of methane" a "substantial release of gas" to be "vented into the atmosphere".
The report said the small sample size meant that the results "may not be representative of the industry overall", and added that it was "important to view the results of this study in this context".
The report only measured emissions from the completion itself; other well construction processes including drilling and fraccing were been examined.
It noted, however, that fraccing and the subsequent liquid flowback period have been identified as one of the main emission routes from unconventional gas production in the US.
"Although this technique is not common in Australian CSG production, it is still important that measurements be made to determine the full extent of methane emissions from well construction activities," the report added.
Dr Roberts hailed the report as "another important and rigorous study from the CSIRO whose previous research in 2014 found that fugitive emissions from CSG wells were only a tiny fraction (0.02%) of CSG production".
"While the study notes there are a number of other areas requiring further investigation, it is significant that these initial findings based on actual measurements show emissions from well completion operations are relatively small, and in some cases negligible," he said.
"It continues the range of reports in recent years that have shown that the environmental concerns about CSG raised by various activist groups do not stand up to scrutiny.
"Natural gas has around 50% fewer emissions when used in power generation than traditional energy sources. There are substantial environmental benefits associated with expanding natural gas production, including CSG production. "
Yet Hogan noted that just 24 hours at that one workover rig at one well released the equivalent of 525t of CO2 - "a fairly alarming rate of methane venting, considering it may not be properly accounted for by the government currently".
"There are thousands of CSG workovers occurring in Queensland, it's an ongoing procedure that can range from replacing well tubing or pumps, or resetting a well due to changing flow conditions," she said.
Hogan said the study did not examine the emissions from drilling, hydraulic fracturing and the liquid flowback period, despite, as the report admits, those practises "have been identified as one of the main emission routes from unconventional gas production in the United States".
"Top down satellite measurements of unconventional gas fields in the United States show methane emissions to be 5%-17% of total gas production - a dangerously high methane figure that should be investigated fully in Australia," she said.
Industry figures point out, US shale developments are different from Australian CSG, both in terms of the techniques used and the geology from which the hydrocarbons are being extracted.