Hydraulic Fracturing, or “Fracking” as it is commonly known, is the process by which subsurface rock formations containing petroleum resources are intentionally fractured by high pressure sand, water and other fluids in order to allow the trapped oil and gas to be recovered. Although fracking has been used for decades, the process has recently been making headlines across the United States and Canada for causing drinking water contamination, particularly in the Marcellus Shale in the eastern United States. As a result, much research is being conducted on how freshwater resources are contaminated by fracking and what the effects of the contamination may be. This case study will briefly explain each step in the fracking process as well as the potential effects fracking may have on freshwater resources.
The first step in the fracking process involves acquiring large quantities of water to be mixed with sand and various other fluids to become fracking fluid in step two. The water from can either be acquired from surface or groundwater sources depending on availability. In some particularly arid regions the amount of water required can stress the environment or negatively affect drinking water in the region. The damage to freshwater resources at this stage can be minimized through reuse of the water for subsequent fractures.
During step 2, the fresh water is mixed with sand and chemical additives to create fracking fluid. The chemical additives used are highly variable between well and company and over 1000 different chemicals are used overall although generally no more than 30 per well. Some examples of common chemical additives include: Methanol, petroleum distillate and hydrochloric acid (FracFocus). The additives serve various purposes including preventing bacterial growth and lubrication. The danger to freshwater resources at this stage can be mitigated through proper training and handling of the hazardous materials to prevent accidental spills.
Step 3 sees the fracking fluid injected below the surface at very high pressures to fracture a petroleum bearing rock formation to allow natural gas to be recovered. The danger at step 3 come mostly form improper well management resulting in contamination of groundwater and aquifers. This can occur through fracturing into an aquifer or through migration of fracking fluids into freshwater aquifers through natural or man-made (old wells, etc.) channels underground. Proper well creation and management are paramount to prevent damage at this stage.
Once the fracking fluid has been injected and pressure is released, step 4 beings. During step 4, flowback and “produced water” are collected. Produced water is any extra fluid that returns to the surface as a result of the fracturing of the formation. Flowback includes natural gas and highly saline water that was trapped within the rock as well as the fracking fluid. All of this fluid must then be stored so it can be treated for recycling or disposal. Proper handling and prevention of leaks and spills of the waste fluids can prevent further freshwater contamination.
Finally, the waste fluids are either treated and releasing into surface water, recycled to be used as fracking fluid again, or disposed of by injecting it back underground. Risk of freshwater contamination at this stage can occur through spills during transport to the disposal or treatment location but also through improper or insufficient treatment and subsequent release into the environment.
Throughout the fracking process there are risks to freshwater resources. However, these risks are relatively unlikely to occur. The most likely steps within the fracking process to result in freshwater contamination are those that involved human handling and transport of fracking fluids. With proper training and handling of the hazardous materials involved, these surface based risks can be all but eliminated.