What is shale gas?

Shale gas is a form of natural gas extracted from deposits in shale rock. It is no different to natural gas from other reserves. Fossil fuel companies extract it for exactly the same purposes. Burning it generates electricity, powers homes and supplies gas stoves. Heavy industries also use it to make materials and chemicals. Only the extraction process is different.

Natural gas from all sources is a mixture of different compounds. The colourless, odourless gas contains small quantities of natural gas liquids and nonhydrocarbon gases, such as CO2 and water vapour. But, the main component, accounting for roughly 70 to 90 per cent of its makeup, is methane. 

Methane

Methane is an extremely potent greenhouse gas. It has a 100-year global warming potential that is 28-32 times higher than carbon dioxide (CO2). Over a 20-year period, methane’s global warming potential skyrockets to 84-86 times that of CO2. The production and use of all natural gas, including shale gas, contributes substantially to global warming. This is largely due to fugitive emissions in which methane leaks into the atmosphere. These leaks occur at every stage of natural gas production, from extraction to end use.

Australia’s ‘gas fired recovery’

Natural gas from shale deposits and conventional reserves is responsible for almost one-fifth of Australia’s measured greenhouse gas emissions. Yet, the country is currently investing millions into dirty fossil fuels as part of its ‘gas-fired recovery’ to the COVID-19 economic crisis. This is despite the fact that renewable energy is cost-competitive with gas, and it would be cheaper to transition from coal straight to green energy sources.

Coal seam gas and other unconventional sources

In fact, it would also be cheaper for most Australians to use electricity instead of gas in their homes. The majority of Australian states have now depleted their conventional natural gas reserves. This leaves deposits of shale gas, coal seam gas and other unconventional sources, which are more expensive to extract. Consequently, the government’s funding of gas and not renewables is likely to result in stranded assets that will not produce a viable economic return. 

Map of global shale gas reserves

Natural gas as a ‘bridge’ fuel

Natural gas was once considered a ‘bridge’ fuel between coal and renewables. This is because it generates fewer CO2 emissions per joule of energy than coal. However, research has shown quantities of methane released by natural gas to be up to 40 per cent higher than previously thought. If enough methane leaks during production, it cancels out any environmental advantage that natural gas has over coal. 

Methane already accounts for 20 per cent of global emissions. 60 per cent of these come from human activities, including shale gas production. If we continue to expand the use of fossil fuels, like gas, we will miss climate targets and cause catastrophic damage to the planet. Yet, this is exactly what Australia is doing.

At COP26, the US and EU put forward a global pledge to cut methane emissions. More than 100 countries committed to the pledge. However, Australia refused to join.

How is shale gas different from natural gas?

Shale gas has the same composition as natural gas. The difference is that it formed in a distinct rock formation. Subsequently, it requires an alternative extraction approach. Unconventional deposits are found in rocks and soils with low permeability and, therefore, do not easily transmit fluids or gases. In contrast, conventional reserves are in rock formations that are porous with high permeability. Conventional sources of natural gas include sandstone, siltstone and limestone. 

How does shale gas form differently to conventional gas?

All natural gas forms from decomposing organisms, like plants and animals, from millions of years ago. Their remains create a layer and mix with sand and silt. Buried beneath the surface of the Earth, they were exposed to intense heat and pressure. Over time, this changed them into materials, such as coal, oil or natural gas.

Once it forms, natural gas tries to migrate towards the Earth’s surface. Some gas succeeds and finds its way to the atmosphere. But, when it cannot reach the surface, conventional and unconventional reserves form. 

Conventional deposits

For example, conventional deposits form when natural gas escapes its organic-rich source formation and reaches a highly permeable reservoir. If there is an overlying layer of impermeable rock, the gas is trapped there until a fossil fuel company comes and drills into it.

Unconventional deposits

On the other hand, shale gas deposits form within organic-rich shale rock. The shale prevents the gas from escaping to either the surface or to more permeable reservoir rocks. Subsequently, the deposit forms within the shale itself. Shale gas remains within the pores of this sedimentary rock until horizontal drilling, and hydraulic fracturing releases it.  

Why is hydraulic fracturing necessary in shale gas production?

Due to the nature of shale deposits, hydraulic fracturing (or fracking) is necessary for shale gas production. Hydraulic fracturing is a technique for extracting oil and gas from impermeable rock formations. It involves injecting large quantities of water, sand and chemicals into these unconventional deposits. The intention is to both create new fractures in the rock, and increase the width and connectivity of existing fractures.

By enlarging or creating new fractures, fracking increases the permeability of a rock formation, like shale. It, therefore, increases the flow of oil or gas to a well from these hard-to-reach deposits. Companies also employ horizontal drilling to access more of the resources. 

Steel pipes and cement stabilise the well. They prevent soil and water from contaminating the fossil fuels. The process makes it easier to extract the gas or oil from unconventional sources.

Fracking equipment for shale gas extraction

How is shale gas production different from conventional natural gas production?

Natural gas is typically produced from onshore and offshore wells and from coal beds. In the conventional reservoirs, the gas can flow easily through wells to the surface. Wells may be drilled vertically and horizontally in geological formations with profitable quantities of natural gas. 

Vertical drilling is most efficient where natural gas is close to the surface. The average depth of these wells is between 300 and 800 metres. Horizontal drilling is a technique to increase the production of a well. It requires changing the direction of a drill once it has reached a particular depth. This helps to reach more gas or oil that may not be located directly beneath a well.

Is shale gas fracking ever sustainable?

Methane emissions from shale gas fracking

Shale gas production increases the amount of methane in the atmosphere. It leads to greater consumption of the fossil fuel, causing more greenhouse gas emissions. The oil and gas industry was responsible for about 70 million tonnes of methane emissions in 2020. This represents over five per cent of all energy-related emissions. The production of any fossil fuel cannot be sustainable.

Wastewater issues with shale gas fracking

Hydraulic fracturing is also an unsustainable practice in itself. It uses vast amounts of water. Australia is already “on the brink of a water crisis”. Using significant volumes of water for fracking can lead to shortages for local human populations. It can also destroy aquatic habitats.

Equally harmful, fracking produces an enormous amount of wastewater. This water is brought to the surface and contains both artificial and naturally occurring chemicals. These include ​​endocrine-disrupting chemicals (EDCs), polyaromatic hydrocarbons and volatile organic compounds. 

Shale gas fracking and chemicals

Prenatal exposure to fracking chemicals is linked to adverse reproductive and developmental outcomes in female mice. The harmful chemicals can remain in the environment for decades. Even exposure to small quantities of some of these chemicals can cause cancers and nervous system disorders.

Fracking runs the risk of contaminating groundwater with dangerous and toxic chemicals. Therefore, it is imperative that they are managed responsibly. However, in Australia, endocrine disruption research lags behind North America and Europe. There are serious concerns that safety measures are inadequate.