An investigation into gas seepage from the Condamine River in southern Queensland has returned no conclusive results.
The report was published last week by Australia Pacific LNG (APLNG), summarising the scientific investigation conducted by Norwest Corporation.
The ‘Condamine River Gas Seep Investigation: Technical Report’ list four reasons for the seepage of methane from the river beds near Chinchilla, Queensland, which was first reported by local fishermen in February 2012.
Causes detailed in the report include repressurisation from the impact of flooding and aquifer recharge; fractures, faults and springs, which are natural pathways for water and gas; ‘capping and trapping’ from geological structures; and depressurisation, which can either be caused by drought, or by the human impacts of CSG well drilling, and other drilling activities that tap through coal seams including water bores and coal exploration.
The study was subject to an independent scientific review co-ordinated by the Queensland Government’s chief scientist Dr Geoff Garrett, which concluded that investigations undertaken by APLNG were “rigorous and scientifically sound” and that further investigations were warranted to identify the causes.
Origin LNG CEO David Baldwin said detailed investigation into the Condamine River seeps has greatly increased understanding of subsurface conditions.
“Despite there being very little CSG development in the immediate area, the responsible approach is to develop and maintain an ongoing monitoring program, in line with the Norwest report recommendations,” Baldwin said.
APLNG has been carrying out seismic survey analysis, managed by Origin, and is constructing eight monitoring bores at four locations near the seeps, which feature real time telemetry data systems and provide ongoing data on ground water levels and pressures.
The seepage was first identified by recreational fishermen, but was reported by a local landowner and Lock the Gates member Dane Pratzky, who videotaped the phenomenon for reporting by media.
Pratzky reported that another local landowner noticed the bubbles, and had been in touch with government and with Origin, who had already tested the gas and confirmed that it was gas from coal seams.
The phenomenon took the form of bubbles of methane released from the surface of the Condamine River, in four spots along a river stretch of about five kilometres.
At the time of discovery of seepage Origin denied any link with CSG drilling in the area, claiming that there were only four cased gas bores within one kilometre of the site which could not cause the release of gas.
Origin said that the coal seam in that area was only 50-75 metres from the surface, that the nearby wells were cased in cement, and that no fracking had been carried out using those wells.
Image: Courier Mail