The gas exploration company Red Sky Energy has recently claimed its pilot gas production well north of Whiporie is tapping into conventional gas reserves in 'tight sands', when only a few months earlier, they released a report for the Australian Stock Exchange claiming their exploratory drilling had identified unconventional gas.
I believe the gas industry is deliberately trying to confuse the community. Firstly they told us that the environmental and social disasters resulting from shale gas mining in the USA, which was exposed in the award winning documentary 'Gasland', is different to our local resource which is coal seam gas.
Natural gas, conventional and unconventional gas, shale, coal seam and tight sand gas. What does it all mean?
Natural gas is methane, the result of decomposition of vegetation deposits over millions of years. That methane comes from conventional and unconventional sources. The conventional source is methane that has leaked out of the coal seam and become trapped underground in large reservoirs which can be easily tapped by drilling down into it, and pumping it out through a limited number of well heads that can operate for many decades.
Unconventional gas is that methane that has either remained in the coal seam (coal seam gas), or has also seeped out but instead of accumulating in large reservoirs, has then become trapped in other underground shale deposits (shale gas) or, as is the case in the Clarence Valley, in sedimentary sandstone (tight sand gas).
All these unconventional deposits require some level of “stimulation”, i.e. breaking up the underground rock layers to release the gas. This is done using relatively new technology that allows horizontal drilling along the rock seam so that hydraulic fracturing or “fracking” can be undertaken.
Fracking is the process of pumping a mixture of water, sand and a variety of chemicals under extreme pressure to smash up the rock seam. The sand is forced into the cracks to keep them open, and the fracking process may have to be repeated several times over the life of the well, which is generally about 15 years.
Because there is a limit to the distance horizontal drilling can go, an unconventional gas field requires multiple well heads, all connected by above ground pipelines and roads, and the cracking of the rock layers increases the risk of disrupting aquifers and polluting underground water. Methane leaking along the newly formed cracks into the water table, is what is seeing water bores in Queensland spewing out more gas than water, to the point where they can be set alight.
Fracking also leads to methane leaking upwards along those cracks directly into the atmosphere, which are referred to as “fugitive emissions”, and go largely undetected and are unmeasurable. Methane is a potent greenhouse gas. So these fugitive emissions are making a significant contribution to climate change.
Unconventional gas wells are closed down when gas flows drop to levels that are no longer commercially viable. So after some 15 years of production the well is sealed to prevent the remaining methane from escaping. However, those fugitive emissions will continue to flow forever, and the cement casings that line the borehole will all fail over time and also begin to leak methane. In the USA upwards of 50% of sealed wells were found to be leaking within 8 years of being abandoned.
- John Edwards