It's a gas – but which gas is it?

Boudicca Cerese is an environmental scientist and a regional co-ordinator for Lock the Gate Alliance.

The last two years have seen a massive expansion in the coal seam gas industry in eastern Australia with over 18,000 coal seam gas (CSG) production wells approved in Queensland and increasing exploration and production across many parts of New South Wales. In the Northern Rivers more than 13,500 square kilometres is covered by petroleum leases and there are three companies actively exploring for gas. This frenzied growth in CSG operations across the eastern seaboard has been matched by an increasing awareness of the risks associated with CSG extraction and a burgeoning opposition to the industry. However, many people are unaware of the other forms of unconventional gas currently being targetted for exploration locally and across Australia.

Typically, natural or conventional gas is found in large permeable rock reservoirs and can usually be extracted quite readily and easily, whilst unconventional natural gas is gas that is found in less permeable deposits and is therefore more difficult and less economical to extract. Unconventional gas reservoirs have been identified for many decades but commercial development of such fields did not commence in earnest in North America until the mid to late 1970s with an increase in demand for natural gas, increasing prices and significant advances in extraction technologies. In Australia, the commercial production of CSG began in 1996 in the Bowen Basin, Queensland and since then production has increased rapidly, particularly since the early 2000s. According to government sources, as of September 2011 there were 4489 CSG wells drilled in Queensland and 493 in New South Wales.(1)

Many readers would already be aware of the shale gas industry in the US, which was the subject of the award-winning film Gasland. The gas that is found in shale beds is similar geologically to coal seam gas in that the gas is still present in the source rock, not having migrated to a permeable reservoir. Australia's shale gas reserves are currently estimated to exceed reserves of CSG, with exploration for shale gas currently taking place across several states, the most advanced operations being located in the Cooper Basin in South Australia and the region just north of Perth in Western Australia.

Another type of unconventional gas also being targetted for exploration in Australia is tight gas (aka tight sands/sandstone gas). This is gas that is located in a very tight formation underground, trapped in extraordinarily impermeable, hard rock, or trapped in sandstone or limestone formations that are atypically impermeable and nonporous. Tight gas is sometimes referred to as conventional because, geologically speaking, it is held in similar rock reservoirs to typical conventional gas. However, in terms of extraction, it is definitely an unconventional gas as many wells need to be drilled to extract viable quantities of gas and extraction techniques such as fracture stimulation (fracking) are needed to achieve gas flow. The process of acidation is also often carried out following fracking, which involves pumping the well with acids that dissolve the limestone, dolomite and calcite cement between the sediment grains of the reservoir rocks. Exploration for tight gas is occurring in many parts of Australia with significant reserves already identified in the Gippsland region of Victoria.

The gas-bearing structures underlying the Northern Rivers that are currently being explored contain coal seam gas, tight gas and conventional gas. The distinction between tight and conventional gas is not always made by gas companies, with tight sandstone gas reservoirs often simply labelled as conventional. However, publicly available company documents clearly state that 'the sandstone reservoirs of the Clarence-Moreton [Basin] are relatively tight' and 'some or most reservoirs may need some form of stimulation to achieve commercial flow rates'(2). These documents confirm that fracking would be required to make tight gas extraction economically viable in the Northern Rivers.

The Kingfisher gas field underlying the area around Casino contains significant tight gas sections(3), and is the location of the exploration well that was fracked by Metgasco in 2010. Seismic exploration by Metgasco 'indicates the existence of a large number of Kingfisher look-alike conventional/tight [gas] plays'(4), including the Greater Mackellar Structure, which is the target of the seismic testing and exploration drilling planned this year by Metgasco around the Rock Valley/Bungabee areas. The pilot production well that is planned for Red Sky Energy's Talma well site near Whiporie is also targetting tight sandstone gas(5).

Regardless of the type of unconventional gas, the large numbers of wells needed and the invasive technologies used to extract the gas mean that full-scale gas production involves a massive industrialisation of natural and rural landscapes. The strong resistance to this industry in the Northern Rivers makes it abundantly clear that local residents do not want to live in a gas field. Opposition to the proposed industrialisation of our beautiful region has united people from all walks of life and political persuasions into a fast-growing mass movement that is totally committed to achieving a CSG-free Northern Rivers.

1. Pazzano, C. 2012 (SBS World News), Factbox: CSG in Australia.

2. Bailleau Research, 2011, Initiation of Coverage: Metgasco Ltd. by Bailleau Stockbroking.

3. David Johnson (Metgasco managing director) 2010, "Presentation to Rodman & Renshaw Conference".

4. Bailleau Research, 2011, Initiation of Coverage: Metgasco Ltd. by Bailleau Stockbroking.

5. Red Sky Energy, 2011, ASX Announcement, Resource Study Confirms Prospectivity.

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