Fracking case study: The Marcellus Shale

The map below shows the vast number of shale deposits in the USA. Estimates of the potential natural gas reserves in these deposits could meet America’s energy needs for 90-116 years (Karbo et al 2010). For a country that has been one of the top importers of energy for the last decade there is huge appeal at the potential of being self-sufficient. Little wonder then the dramatic investment in hydraulic fracking technology: currently the only way to access the shale gas reserves. 

I am going to look at the case of the Marcellus Shale: by far the biggest reserve in the US and a hotly debated issue. It lurks beneath 10 states including New York and Pennsylvania then crosses the border into Canada.

Shale deposits of America (Image from Kerr, 2010, Science Volume 328)

The formation is about 400 million years old (Devonian era) and the black colour comes from the organic rich material. Setting up the horizontal drilling wells has proved to be expensive, costing $3-5 million each. Yet the income generated from the industry is huge: in Pennsylvania alone, extraction of natural gas has generated 29,000 jobs and bought huge revenue through taxes and investment. This is a little shot of the actual deposits from the Marcellus Shale containing the natural gas. 

Sample from the Marcellus Shale (image from Environment, Science and Technology Journal 2012)

Challenges of the Marcellus Shale

• Most of the gas is about 1.6km below the surface – the challenge of drilling increases with depth as rock hardness and pressure increases. Therefore the drill bit has to be replaced regularly and the therefore process is very slow. Up to 50% of the drilling cost is consumed by drilling the last 10% of the well.
• Protection of the natural flora and fauna at the surface – there are limits to the horizontal reach of each well to maximise extraction numerous wells across a wide area are installed. There is also a lot of new infrastructure and transport links that have been constructed
• Secure cementing of the well - this is essential to prevent leakage of gas or fracking fluids. Given the depth and temperature of the wells in the Marcellus Shale (35-51C) this is very challenging. It is believed that this led to the leakage of methane into local groundwater (Vidic et al 2013).
• Water consumption in extraction – up to 10 million gallons of water are required to complete the extraction per well. Transporting this much water has huge energy costs and also raises moral issues in periods of drought when water is needed for agriculture.  

Opportunities that are being pursued

• Advancements in drilling – using multilateral rather than horizontal drilling for more efficient access to the gas. Also using paraffinic fluids rather than diesel to reduce the amount of atmospheric pollutants by 85% (Karbo et al 2010)
• Using environmentally friendly fluids – using plant oils such as palm or soy instead of chemical based (Fracking Report 2008) 
• Improved drinking water – increasing monitoring and treatment of drinking water to ensure the local communities are not harmed and to increase public support for the industry

Overall, the business here has been hugely successful and given a huge boost to the local economy. It has produced 12% of all natural gas in America and this figure is predicted to increase for many years despite the controversy around the site.

Finally, it is just me or does the picture of the sample from the Marcellus Shale look a bit like a choc ice?

Meet the Frackers - Part 1

“Meet the frackers” has become a popular name for news articles, TV documentaries and campaign groups linked to fracking. Over the next few weeks I am focus on fracking for my blog posts. Firstly lets introduce the process of hydraulic fracturing for oil and gas and address two of the key issues the process has raised.

Hydraulic fracking is a process where fluid is pumped into rock at high pressure which causes the rock to fracture. This creates more space within the rock and allows oil and gas to percolate through the formation therefore it can be pumped to the surface and extracted. It has been used in the USA, extracting gas from areas such as the Marcellus Shale, for the last decade and has recently been given the green light by the UK government.

Video: BBC Horizon programme "Fracking: The New Energy Rush" 

Issue One: Does fracking cause earthquakes?

The honest answer: yes it can. The more the more important question is do these earthquakes matter and can they be avoided? Recorded earthquakes induced by hydraulic fracturing have a magnitude in the range of 1.0 – 3.8. This causes comparable ground shaking to a large articulated lorry driving past your house. Much higher magnitude earthquakes have been recorded from the use of controlled explosions in mining, up to 5.1, and from reservoir impoundment where the weight of the water causes ground fracturing, up to 7.9. (Davis et at 2013). So the earthquake damage cause by earthquakes induced by fracking doesn't even come close to other anthropogenic causes. 

Even if the earthquakes are small, it is important that oil and gas companies do all they can to avoid it in the first place. This can be achieved by improved research and method in the operations. A review of fracking in the UK was carried out which addressed the earthquakes causes in Blackpool (Royal Society and Royal Academy of Engineers 2012). They recommended that better fault plane analysis could help minimise risk of earthquakes by avoiding injecting fluid directly into fault planes. Overall they gave fracking the go ahead in the UK. 

Issue Two: will fracking contaminate groundwater?

 Image courtesy of John Cole Cartoons (The Times Tribune, Pennsylvania) 

Water contamination has been a huge issue for some US fracking operations. Using geochemical isotropic tracers at a fracking site in Pennsylvania, it was shown that increased levels of methane, chlorine and potassium in groundwater are “related to stray gas contamination directly linked to shale gas operations”. (Darrah et al 2012, Procedia of Earth and Planetary Science). This maybe a case where improved technology and processes can prevent this occurring again however for some communities fracking has already had a severe impact on quality of life.