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hydraulic fracturing
by A. Nonymous
Physical Geology
Fall 2011
            

 

 

Hydraulic Fracturing

 

    Hydraulic fracturing, also known as ‘hydrofracking,” is a method of natural gas extraction that has recently come under scrutiny for it’s potential threat to the environment, with ground water contamination being the primary concern.

 

     Natural gas has become an increasingly popular energy source since the 1970’s. It is touted as one of the cleanest sources of energy, with fewer carbon dioxide emissions than other types of fuel.   Natural gas can form under a number of different conditions. One method of formation takes place over millions of years as a result of organic materials decomposing and becoming compressed in layers of sediment. This thermogenic process takes place far under the Earth’s crust where temperatures are higher than at the surface.  There is also a biogenic process that happens when microorganisms chemically break down organic matter into methane. This process takes place much closer to the Earth’s surface.

 

Photo courtesy of f03.classes.colgate.edu

 

     Traditionally, gas companies have used vertical drilling to access natural gas reserves close to the surface. This conventional means of drilling for natural gas has only been able to extract only a portion of the total amount of natural gas in the United States. However, there have been advances in technology that have enabled gas companies to access a larger amount of gas. Two of these advances are horizontal drilling and hydraulic fracturing. When used together, they make it possible to extract what is referred to as “unconventional oil.” Horizontal drills look like a standard vertical drill from the surface, but after drilling straight down for thousands of feet, are able to make a 90 degree turn and drill parallel to the Earth’s surface. This allows for drilling great distances along a shale beds, where they can utilize hydraulic fracturing to release the natural gas in the rock. This type of gas, called “shale gas,” is estimated to account for as much as 20% of our gas supply by the year 2020.

 

     Hydraulic fracturing is the process where millions of gallons of water, mixed with chemicals and sand, are pumped into the well at high pressure, causing the shale to fracture, and releasing the natural gas. The sand serves to keep the fractures open, while a myriad of chemicals serve many different functions, such as preventing corrosion. In the process of hydraulic fracturing, the vertical part of the well is drilled first, which passes through the water table. Companies use cement casings in order to seal the well from the ground water and to prevent contamination. Up to 75% of the injected water flows back out of the well, and so large holding ponds are needed to store this water until it is transported to treatment facilities.

 

Image courtesy of watershedcouncil.org

 

     There is concern not only for the shear amount of water being used in this process, but also for the potential effects on water quality. One concern is that when the cement casings fail, they can cause contamination. Another is that there is potential for the chemicals to be spilled in the removal process. Many people are concerned about the types of chemicals being used. The gas industry is exempt from federal laws enforced by the Safe Drinking Water Act, and they have chosen not to voluntarily disclose the names of all the chemicals they use in hydrofracking. Gas companies claim that the chemicals they use should not be made known to the public, as this would compromise the companies trade secrets.

 

Photo courtesy of wilderness.org

 

     Residents in areas near drilling sites have filed complaints, citing that their drinking water had become contaminated since drilling had started in their area. Oil companies have denied any connection between their drilling practices and water contamination, but several oil companies are providing residents with drinking water. The EPA is currently investigating these reported incidences, and is expected to complete the study by 2014.

 

Photo courtesy of insiderclimatenews.org

 

Sources:

http://www.eia.gov/kids/energy.cfm?page=natural_gas_home-basics#natural_gas_where-basics

http://f03.classes.colgate.edu/fsem037-naturalgas/production.htm

http://fpc.state.gov/documents/organization/117779.pdf

http://fossil.energy.gov/programs/oilgas/publications/naturalgas_general/Shale_Gas_Primer_2009.pdf

http://water.epa.gov/type/groundwater/uic/class2/hydraulicfracturing/index.cfm

http://insideclimatenews.org/news/20111110/epa-fracking-wyoming-aquifer-drinking-water-natural-gas-wells

http://www.watershedcouncil.org/learn/hydraulic-fracturing/

http://wilderness.org/content/hydrofracking-forum-raises-more-questions-about-safety-chemicals