Natural Gas Fracking and the Environment: Fracking Chemicals

A Series on the Environmental Effects of Hydraulic Fracturing for Natural Gas

FracRig_RichLasalle_theImageBank_Getty.jpg
Rich LaSalle/The Image Bank/Getty

High volume hydraulic fracturing, often simply called fracking, is an approach to drilling for natural gas deep in shale rock formations, for example in the Marcellus shale region. There are numerous environmental issues associated with this type of operation, from the nature of the shale formations, the large amounts of water needed for fracking, to the volumes of wastewater that need to be recycled or disposed of.

One issue that has been of major concern for fracking region residents is the problem of fracking chemicals.

During the fracking process, large amounts of water are pumped into the horizontal components of the well. Numerous additives are added to that water, each with a different role. Several tons of frac sand are added to prop open the newly formed cracks in the shale rock. Hydrochloric acid is injected to weaken the shale rock, followed by corrosion inhibitors so that the steel casing is not damaged by the acid. Guar gum, cross-linkers, and breakers are all types of chemicals involved in delivering the frac sand into the shale fractures. Naptha (a high-fraction distillate of petroleum) reduces the friction of fracking fluid in the well. Different biocides can be used to prevent bacteria growth, which might block the fractures. Other chemicals may be added depending on the local geological conditions.

Fracking technology is young, and the process is constantly revised and adapted to increase efficiency, which means the list of fracking chemicals can evolve rapidly.

Are these additives an environmental concern? Several of the chemicals used are harmless, others can have damaging effects at high concentration, while some can be dangerous even at very low concentrations.

Two reasons are invoked by the industry to justify the safety of their use: 1) those chemicals are diluted within millions of gallons of water, and 2) the resulting fracking fluid either safely stays underground, well below any groundwater, or is recuperated at the surface and treated or disposed of.

It is true that the amount of chemicals added represents only up to 1% of the total volume of fracking water. However, this very small fraction still represents, in absolute terms, a large amount: for a single well, 40,000 gallons of additives are pumped in. Handling such large amounts of liquid chemical additives is inherently risky. Accidents can happen while the chemicals are transported by truck. The transfers from tanker truck to reservoir, then reservoir to well, and back out of the well to holding ponds are all opportunities for accidental spills. Chemical additives contribute to the waste water problem, as they are polluting agents when wastewater is spilled on the surface.

When the drilling and fracking process is done well and no problem occurs, the fracking fluid should never come in contact with any ground or surface waters. However, on a non-trivial proportion of wells problems do occur.

One significant issue is the failure of the steel or concrete well casings, allowing fracking water to enter the ground much closer to the surface, leading to ground and surface water contamination. For example, the U.S. Environmental Protection Agency determined that well water contamination for residents of Pavillion, Wyoming, was due to the movement of gas and fracking fluids away from wells and into the groundwater system.

Worse than the fracking chemicals, however, might be the flowback or produced water recuperated after fracking, as it contains very high concentrations of salt, heavy metals, and sometimes radioactive material. These elements originate from the rock formation itself, are much more concentrated in the waste water than the chemical additives are, and probably should be much more of an environmental concern.

Source

Duggan-Haas, D., R.M. Ross, and W.D. Allmon. 2013. The Science Beneath the Surface: A Very Short Guide to the Marcellus Shale. Paleontological Research Institute.