FAQ's Research's Dr Robert Merkel on the what, why and how of coal seam gas.
As the name suggests, coal seam gas is a type of natural gas extracted from coal seams.
Natural gas is a mixture of a number of different gases. At least 80% is methane, a colourless, odourless gas (at normal temperatures and pressures). Methane is the simplest possible hydrocarbon
-- molecules made entirely of a combination of hydrogen and carbon. Depending on the source, natural gas will also contain varying amounts of other hydrocarbons such as propane (which is a major constitutent of the LPG used in cars), carbon dioxide, and other compounds like hydrogen sulphide ("rotten egg gas"). Some of these, such as the carbon dioxide, must be removed before the gas can be used.
Natural gas is extremely widely used. It is the piped gas most urban Australians use to heat their water and cook their food. It is also used to generate electricity, and is used industrially, both as a source of heat and a feedstock in important industrial processes. Ammonia, a key ingredient in fertilizer, is produced using natural gas. It can also be used as a transport fuel, such as the natural gas-powered buses becoming increasingly common in major cities. About 22% of the world’s energy is produced by burning natural gas.
Natural gas has a number of attractive properties as a fuel. It is the cleanest-burning of all fossil fuels. Burning natural gas results in much less carbon dioxide for the same amount of energy as burning petrol, diesel, and especially coal. Furthermore, natural gas combustion releases far, far less of the other major combustion pollutants, such as carbon monoxide, particulates, ozone, and nitrogen oxides, than burning equivalent quantities of other fossil fuels. Globally, these pollutants kill hundreds of thousands of people every year.
Producing electricity from burning gas has other attractions. Gas-fired power stations can be built more cheaply than most other types, and can be started and stopped easily. Therefore, they are particularly useful for “peaking” power stations which are only operated as needed. As intermittent renewable energy sources like solar and wind produce a greater fraction of our electricity in the medium term, this property will be even more valuable.
The combination of natural gas’s attractive features, and the increase in world energy demand, has resulted in a substantial increase in natural gas consumption. This is expected to continue for some time to come.
Coal seam gas: where does it come from?
"Conventional" natural gas is found trapped in rock formations in a similar way to crude oil -- indeed, most gas wells produce a little oil and vice versa. Historically, Australia’s gas supply has come from these sources, from places such as the Bass Strait fields off Victoria’s coastline, and the North West Shelf fields off the far north-west coast of Western Australia. However, with the increase in global demand for natural gas, and the development of technology to liquefy and ship natural gas around the world, there has been much interest in alternative sources of natural gas.
Coal, like oil and gas, is a "fossil fuel" -- it is the fossilised remains of long-dead plants and animals from millions of years ago. While some coal, such as that found in parts of Victoria, may only be a few million years old, Queensland's black coal is far older, in most cases beginning to form 100 million or more years ago. It is the most abundant fossil fuel, both in Australia and globally. Australia has the world’s fourth-largest coal reserves. There are many known coal deposits that are uneconomic to mine directly.
In the chemical reactions that ultimately result in coal formation, natural gas is also formed. Much of it leaks into the atmosphere over those millions of years, but some ends up trapped within the structure of the coal, along with large quantities of water which helps trap the gas.
Coal seam gas is extracted by drilling wells into an underground "seam" of coal, then pumping some of the water out, allowing the natural gas present in the seam to escape and be collected.
When prospecting for CSG, a mining company will first drill an exploratory well, testing whether the area is a good source of CSG. If the test well is successful, multiple production wells will be drilled.
In many areas where CSG prospecting and production are currently occuring including the Surat Basin, companies drill through the aquifers of the Great Artesian Basin, which were formed between 65 and 250 million years ago. In addition, there are many alluvial or sub-artesian aquifers which lie closer to the surface. The GAB and alluvial aquifers are accessed on a widespread basis for agriculture, industry and human consumption on farms and in towns.Controversy around the effects of CSG
CSG is the source of public controversy for a number of reasons.
Much of Australia’s mining occurs in remote areas, a long way from Australia’s cities or areas where high-value agriculture is conducted. The majority of exceptions to this are in long-established mining regions, such as the coal mines that feed Australia's power generators. The rush to extract coal seam gas has seen exploration begin in areas such as south-east Queensland’s Scenic Rim and the Darling Downs, which are more heavily settled, are home to more intensive agriculture, and have not previously undergone major mining activities.
Under Queensland laws, mining rights are separate to land titles, and mining companies can own leases for mineral exploration and production on land that is owned by others. Mining companies believe that the law entitles them to negotiate, or ultimately have access to properties arbitrated if a landowner refuses them access. Anti-CSG activist groups such as Lock The Gate dispute this; in any case, they regard this as an abrogation of the rights of landholders.
Anti-CSG activists claim that the infrastructure and operations of CSG extraction are very disruptive to farm operations anthe lifestyle of affected farmers. The interference can also lead to economic losses which they argue may not be adequately compensated for.
Aside from the obvious environmental impact of the well and pipeline infrastructure, coal seam gas poses a number of other environmental concerns. For example, dewatering the coal seams to produce gas will alter the relative pressures between coal seam aquifers and potable aquifers accessed by farmers and others. This may cause water to flow between aquifers where it did not do so previously. There is a fear that levels of bores may drop or fail. Moreover, it is known that adverse effects may be delayed and only appear decades into the future.
The water from the coal seam may contain a number of potentially dangerous and damaging contaminants. Most obviously, the water is quite saline. Were this salt to escape into surface rivers or currently used aquifers, it could severely damage downstream ecosystems, render water undrinkable for livestock or human consumption, and make farmland useless for agriculture, even after the cessation of mining. Anti-CSG activists claim that the water may also contain heavy metals such as lead or uranium, as well as various toxic hydrocarbons.
Gases, most notably methane itself, may leak from around the wells. Aside from anything else, this represent a potential fire risk. Methane is a potent greenhouse gas if it escapes into the atmosphere. If leakage rates are high enough, the total contribution to the greenhouse effect of CSG could actually be worse than burning coal.
Furthermore, for the coal-seam gas to reach the well for extraction, it must travel through the coal. Solid coal itself is impermeable to natural gas; the gas must travel through fractures in the coal. If the coal is not sufficiently fractured, “fracking” is used to artificially create fractures. A combination of water, sand, and a variety of chemicals are pumped through the well to create and maintain additional fractures in the coal, allowing the well to collect more gas at a faster rate.
As well as the additional risks of cross-contamination of water supplier, the chemicals used in fracking are in themselves claimed to be potentially toxic, and if cross-contamination occurs these chemicals may end up in currently used surface or bore water supplies.
For all these reasons, CSG is an extremely politically contentious issue, sometimes drawing together individuals and groups who on many other issues are fierce opponents, and presenting thorny questions for all of Australia’s political parties. Federal opposition leader Tony Abbott, for instance, gave a radio interview with conservative talk radio host Alan Jones in which he supported Jones’ proposition that farmers should have the right to refuse CSG prospectors access to their land, only to retract the position soon afterwards.
CSG will be a major issue in the upcoming Queensland election, with the opposition Liberal National Party already announcing a policy that would protect parts of the Scenic Rim from exploration. They also propose to increase the financial returns to local communities and landholders affected by CSG exploration: however, their announced policies would not give farmers the right to refuse access to their land. The incumbent Labor state government has generally been supportive of the CSG industry, but has introduced limited restrictions on access to some agricultural land. The Australia Party, the newly created party led by federal MP Bob Katter, not only supports giving farmers the right to “lock the gate” on CSG access, it proposes a 12-month moratorium on all CSG development, and a variety of other restrictions.
Federally, the Australian Greens have introduced legislation which (if passed) would give farmers the right to refuse CSG explorers access, and called for better science to allow more informed decisions on the benefits and environmental and social costs of CSG development.
*Dr Robert Merkel is a Lecturer in Software Engineering at Monash University. Read more about FAQ Research authors here.