Hydraulic fracturing, called fracking for short, is a mining process designed to release gas and oil trapped in bituminous sedimentary rock formations. Fracking is seen by many in the oil and gas industry as an opportunity to establish energy independence for countries that have vast reserves of bitumen trapped in deep sedimentary rocks.
Fracking technology works as follows:
- A well bore is drilled into a bituminous rock formation.
- The entry well is vertical but to maximize the return horizontal drilling occurs underground within the rock formation.
- A double concrete liner is placed within the initial well bore to minimize contamination of local aquifers.
- A slurry composed 99.5% of water and sand with the remaining portion containing acids and surfactants is injected with pressures up to 10.34 Mega pascals, equivalent to 1,020 atmospheres or 15,000 psi. The high pressure slurry breaks the chemical bond between the rock and bitumen releasing it as natural gas or oil depending on the nature of the rock formation.
- The released bitumen rises under pressure or is pumped to the surface for collection.
- Along with the gas and oil comes the water and chemicals used during the fracturing process.
- This waste water may contain in addition to benzene, toluene, ethyl-benzene and xylene, radium, methane, heavy metals and other toxic substances.
- Waste water may be treated on site in holding and containment ponds or be pumped into trucks and taken away for treatment and disposal. In many cases it is pumped back into the well as a way to increase wellhead pressure and improve oil and natural gas yields. If toxic water gets dumped in nearby streams or if it breaches containment ponds it can contaminate watersheds.
- Where fracking releases natural gas under pressure a byproduct at the wellhead may include airborne chemicals that could be toxic upon prolonged exposure to those working on site or living nearby during exploration and production phases.
So what we know about fracking is the potential polluting effect of the process. Safeguards to address the hazardous chemicals that are byproducts of the process can be monitored and regulated.
But two consequences of fracking that are little understood keep on cropping up. They are:
- Fracking has been associated with contaminated drinking water on farms and in urban centres downstream from drilling sites.
- Fracking has been blamed for a rise in earthquakes in areas where drilling occurs.
Contaminated Drinking Water
When fracking releases oil and natural gas from bituminous sedimentary rocks it also releases other bounded chemicals. In the process of extraction, however, there are numerous complaints about toxic chemicals and methane entering local wells even though they are drawing water from much higher underground sources than those targeted by fracking. In the movie, Gasland, a documentary looking at hydraulic fracturing, the film shows dramatic images of tap water laced with methane that can be lit with a match. Although the fracking industry denies the claim there are numerous cited examples of drinking water contamination in areas where drilling has occurred.
The industry claims that any water pollution evidence comes from variability in fracking methodology around cementing the casing and lining of the well bores. In areas where the bituminous layers are well below the aquifer that water wells draw upon, and sedimentary limestone layers act as barriers to seepage, the industry claims that occurrences of chemicals in drinking water have nothing to do with fracking.
Earthquakes Linked to Fracking
In a 2011 report entitled, Are Seismicity Rate Changes in the Midcontinent Natural or Manmade?, a U.S. Geological Survey team writes that since 2001 there has been a six-fold increase in the average number of earthquakes occurring in the mid-continent. The rate of increase is unprecedented in recorded history and the authors believe the cause is primarily from the well-site injection of fluid used in hydraulic fracturing.
Recent earthquakes in Ohio have resulted in lawmakers temporarily banning fracking in the state. On New Year’s Eve of 2012 a 4.0-magnitude quake was attributed to a fracking process in which waste water collected during drilling was disposed of by injecting back underground for disposal. Previously thought to be a safe practice, geologists and seismologists now believe that this particular practice should be banned.
In November 2011, Oklahoma experienced a 5.6-magnitude earthquake damaging 14 homes. The quake was followed by a number of aftershocks. Oklahoma is normally seismically stable averaging about 50 small quakes annually. But since 2009 that number has suddenly spiked to 1,047. What has been the big change in Oklahoma? Experts point to hydraulic fracturing. Although experts believe the large quake may have nothing to do with fracking, the enormous increase in minor quakes is too coincident with drilling and injection well activity within the State. Oklahoma is home to 185,000 drilling wells and hundreds of injection wells. Waste water injection is considered the primary culprit in this state as well.
Is there a smoking gun to absolutely prove the causal link? Not yet, but there sure are a lot of bullet casings on and underground to suggest a correlation.