THE Queensland Government is asking landholders to monitor the performance of selected bores on their properties through CSG Net, a community-based initiative which seeks to add 1000 groundwater-monitoring points in the Surat Basin to the existing 500.
Among the first sites to be monitored will be oil and gas bores sunk in the 1960s in the Wallumbilla South area, where landholder Lee McNicholl believes approaching CSG production could liberate additional methane gas and interrupt bore flows used to water stock.
Drilled in the 1960s when companies were looking for conventional gas, the bores went down to 2000m, but only the top 150m were fully cased, leaving substantial interconnectivity between various aquifers.
"As a generalisation, they might have been plugged at 700m with concrete to stop gas and water from deeper aquifers coming up."
But as the dewatering of the Walloon Basin for CSG production gathers pace, the Department of Natural Resources and Mines' CSG Compliance Unit (CSGCU) officers, as well as landholders, are increasingly concerned about how the old bores might be affected.
"In these old bores from 150 to 2000m, there is a huge capacity for interconnectivity between various aquifers, and therein lies the problem," Mr McNicholl said.
Apart from destabilising the security of water supply, Mr McNicholl said gas build-ups are dangerous because of the potential of high methane content.
"Once the amount of methane reaches a certain level of 5 to 15 percent in the atmosphere, that's the explosive range, and if you get an ignition source, there's an explosion. CSG companies know they are of concern."
As drought continues to tighten its hold in much of Queensland, the effect of gas blockages in poly pipelines running from bores to troughs is also of concern, as it jeopardises the supply of artesian and sub-artesian water to stock.
The CSG Net program asks landholders to record static water pressure and standing water depth in bores on a monthly basis, and to send the results to the CSGCU.
"CSG Net is a big step in the right direction," Mr McNicholl, who is based at Arklow, Dulacca, said.
Mr McNicholl said Santos had submitted an EIS for the Wallumbilla South area and was now offering to plug and abandon some old wells, at a cost of up to $1 million each, and replace them with new bores to provide stock water.
"These old wells are potential methane vents, and the CSG industry realises this is a ticking time bomb in terms of becoming a safety issue and a landholder dispute issue," he said.
"It's a reassuring step by the CSG Compliance Unit to take this proactive monitoring approach to water levels and pressure with us."
