The process of hydraulic fracturing (also known as fracking) has been used extensively to allow gas to be produced from previously uneconomic shale gas resources. The process begins with drilling a well vertically, and once the desired depth is reached the well is then drilled horizontally. After pipe has been inserted into the well and cemented in, perforations are made in the pipe and cement in the sections where gas flow is desired using a device called a perf gun. Next a mixture of fluids including water and chemical additives are pumped into the well at high pressure. The fluids flow through the pipe and out the perforations. Given the high pressure of the fluids, this causes fractures in the rock. In addition to the fluids, a solid material like sand or beads is injected to prop the cracks open. When the fluids are pumped back out of the well, gas flows into the pipe through the newly created fractures and then to the wellhead. This process can often allow economic gas production in formations that otherwise would not be economic to produce.
The gas and oil industry has used hydraulic fracturing for more than 60 years. There is no doubt that improved hydraulic fracturing, combined with new horizontal drilling capabilities, has unlocked huge amounts of economic gas supply. But lately, increased use of hydraulic fracturing has become controversial due to drilling in closer proximity to populated areas and public campaigns waged by opponents who believe it causes unacceptable environmental risks.
Like all industrial processes, there are risks. These include:
- Disposal of fracking fluids — Anywhere from 15 to 80% of the fracking fluids are returned to the surface and must be disposed of. The fluids include chemical additives that are used to improve the fracking process and may also include additional substances absorbed from the underground formation. Until recently, the production industry has been reluctant to reveal what chemicals are in the fracking fluids, which must be disposed of in a safe manner. In a few limited cases, humans appear to have had severe reactions after contacting fracking fluids.
- Migration of fracking fluids and/or natural gas into water supplies — If the process is done properly, fracking fluids and produced natural gas cannot leak into water supplies because fracking is performed at much lower depths than the water tables and pathways into aquifers are sealed off by cementing. In a few documented cases, improper drilling techniques and surface spills have resulted in limited water contamination.
- Leaks of greenhouse gases — Studies have suggested that the fracking process can result in significant release of methane during the development process. Methane is a significant greenhouse gas. This is an area under research now and it appears that industry practices may need to change to reduce leaks.
- Creation of local earthquakes — In some cases, fracking fluids are disposed of by drilling a well and forcing the fluids underground. In certain formations, it appears that this can cause earthquakes, including some of significant magnitude. Research is ongoing to determine how to best regulate wastewater disposal or otherwise prevent this from occurring.
- Impacts on air quality — Drilling activities traditionally use diesel generators and engines, which are not subject to the same regulation as diesel passenger vehicles and trucks. It appears that in some regions with intense drilling, air quality degradation including raised ozone levels has resulted.
Different regions around the world have taken different positions on hydraulic fracturing for natural gas production. Some allow it with minimal regulation, some allow it with rather strict regulation, and some have entirely banned it. Examples of jurisdictions banning it as of 2020 include multiple U.S. states including New York and countries such as Bulgaria, France, Germany, and Ireland.