Hydraulic Fracturing: What the Frack is that?

Fracking: You might have seen it on the news, driven past a gas well, or read a terrible pun on it, but what exactly is it?

In the United States, reasons for fracking largely come down to economics. From 2007 to 2013 gas bills have dropped $13 billion, and traditionally depressed areas where fracking takes place, like Arkansas, have experienced a significant economic boost. However, there are also significant environmental concerns, such as the lack of regulatory oversight and the contamination of drinking water wells, confirmed by a report published this year from the US Environmental Protection Agency (EPA). A controversial process, hydraulic fracturing is a method to extract oil and [primarily] natural gas.

So what exactly is natural gas?

Natural gas is a type of fossil fuel — fossil fuels are made from animals and plants that have decomposed over millions of years. There are three main types of fossil fuels: coal, which is made from the decomposition of trees and other plants in prehistoric swamps; oil, made from prehistoric aquatic organisms that were buried under sediments; and natural gas, made from the same aquatic creatures but buried deeper under the earth and cooked at higher temperatures and pressures.

Origin and functions for three fossil fuels, coil, oil, and natural gas
Sources: Environmental and Energy Study Institute, US Department of Energy, and American Petroleum Institute

It’s an energy source that has been used since the 1800s. Burning natural gas produces half as much carbon dioxide (CO2) as coal and a quarter less CO2 than gasoline, reported by the US Energy Information Administration as of June 2015, though it does create much more methane, which is also a potent greenhouse gas (see our article on greenhouse gas). According to the Shift Project, which provides access to energy and climate statistics, fossil fuels make up the largest percentage of energy consumption in North America, with coal at 16%, gas at 30% and oil at 41% during 2014.

Diagram of drilling and pipe setup
Source: Kansas Geological Survey, Schlumberger Testing Services, and Shale Stuff

Because natural gas is formed at high pressures and deeper within the earth, we have to be able to extract it in some way. However, this gas is trapped within the rock structure thousands of feet under the surface, so it is under immense pressure. In order to extract the gas from the rock, we have to disrupt structure in some way. First, a wellbore is drilled into the ground. This wellbore has a pipe casing that increases in thickness the closer it gets to the surface of the earth. Then the casing is “perfed.” A perforating gun is lowered into the pipe and it delivers an electrical current into the casing. This current makes small holes in the casing and the cement. These holes are the exit route for the fracking fluid into the rock structure, which is delivered down the pipe once it has been perfed.

Fracking fluid is a mixture of different chemicals and a proppant — solid material such as sand that “props” the fractures in the rock open. The liquid is pumped down the pipe. The rate at which it is pumped into the earth must exceed a certain threshold, known as the “fracture gradient.” The fracture gradient is how much the pressure increases with depth, based on the density of the rock. Essentially, the pressure from the liquid must be enough to compete with the pressure from the rock above. Because the rock is semiporous, the liquid has somewhere to flow.

There are a lot of unknown components with fracking because these chemicals cannot be regulated

The liquid enters the existing pores and expands them. The proppant keeps the fractures open during the extraction. The gas flows through the sand into the pipe, where it and the fluid can be reextracted. By widening the cracks in the earth, the natural gas is released and it can be drawn back up the pipe.

Generic categories of ingredients for fracking fluid
Sources: International Atomic Energy Agency of Vienna, Rick McCurdy and Debra McElreath of Chesapeake Energy Corporation, and Carl Montgomery (2013). Fracturing Fluid Components, Effective and Sustainable Hydraulic Fracturing, Dr. Rob Jeffrey (Ed.), ISBN: 978-953-51-1137-5, InTech, DOI: 10.5772/56422.

Once the chemically contaminated fluid has been reextracted, it is either injected underground or sent to a wastewater facility. However, these facilities are often privately owned, and the wastewater produced by fracking is not what they typically deal with. Consequently, there have been incidences of the facilities’ operations being disrupted and the water even being released untreated back into surface waters. Standards for the treatment of this waste were only proposed April of this year.

As we tap out the easily accessible natural gas wells, we’ve started trying to extract gas that is less easy to access. An example of this is shale gas. In 2000, shale gas made up a mere 1% of the United States’ energy consumption — by 2010 it was up to over 20%. This increase can be attributed to an increase in public interest. In the mid-2000s shale gas was identified as a significant underutilized resource, and unconventional drilling rates increased.

Shale, a sedimentary rock, is much less porous than other types of rock formations. The consequence of this is that the gas is much more difficult to extract. The bore is drilled down into the earth, but instead of extracting the gas back up vertically, the pipe instead is built in the horizontal direction at a kickoff point, running parallel to the direction of the rock containing the shale gas. These laterals can extend for up to two miles underground. This means that a small area above ground can host many pipes.

So, what’s the problem? There are a lot of unknown components with fracking, both long and short term. In the short term, because they are proprietary, gas companies are not required to divulge the components of fracking fluid to the EPA. Different companies use different ingredients and they often change from borehole to borehole, even within the same company. Because these chemicals cannot be regulated, there’s no way of knowing if they are toxic to human health. Furthermore, although they should be below the reach of ground water, there are documented incidents of groundwater contamination traced back to shale fracking. One way it can contaminate local water sources is if there is a crack in the casing near the water level. The fracking fluid is delivered down the pipe, and some of it escapes into the water line and contaminates local wells. It also creates local air pollution, which can exceed safe toxicity levels (see this report by the Texas Commission on Environmental Quality). The disposal of fracking fluids into underground aquifers has triggered even earthquakes, because the fluids get trapped in the semi-porous rock, making it easier for the plates to slide against each other.

Despite the environmental and regulatory concerns with fracking, the fact of the matter is that it’s a lucrative process. With the Keystone Pipeline development being stopped and the United States slow to invest in renewable energies, it seems fracking is here to stay– at least for now.

What is your opinion on fracking?


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