Hydraulic fracturing, or fracking, is a multistep extraction process in which fossil fuel-bearing rock formations are drilled and fractured using huge amounts of water. Oil and gas reserves that were at one time considered inaccessible are now available to be exploited. While the fracking process has expanded oil and gas development, it has also expanded risks to water resources.
The Explosion in US Shale-Oil and Shale-Gas Production
The United States is home to vast quantities of shale-oil and shale-gas, with estimates of natural gas reserves among the largest known in the world. New technologies in petroleum exploration and extraction – most notably the process of hydraulic fracturing (aka “fracking”) – have unlocked unconventional oil and gas stored in impermeable shale-rock formations deep underground, making previously inaccessible deposits easier to reach. US oil and gas production was flagging before the so-called Shale Revolution took hold and spurred the country on to become the world’s top producer of crude oil and the overall leading producer for hydrocarbons (oil and natural gas).
Fracking also shook up US electricity generation. Natural gas surpassed coal and is the country’s largest fuel-source at nearly 32 percent. Often referred to as the “bridge fuel,” natural gas – at least according to the oil and gas industry – will aid in the country’s energy transition from coal to renewable sources like wind and solar. Natural gas use and production has soared in recent years, but so too has the controversy surrounding the environmental, public health and social impacts of how the fuel is obtained.
What is Hydraulic Fracturing, aka Fracking?
Hydraulic fracturing, or fracking, describes a multi-step oil and natural gas extraction process, in which the fossil fuel-bearing rock formations are directionally drilled both vertically and horizontally. Once the well is drilled, a charge is detonated to blast fissures open, then a proprietary mix of water, chemicals and proppants (like sand, these are designed to keep the fissure open) are injected into underground rock layers at high pressure in order to further fracture the rock. Once the production well is fully open, some “produced” wastewater flows back to the surface, and finally, the oil and natural gas is extracted.
Vital to the fracking process are the millions of gallons of fracking fluid for each well, a fluid made up of over 90 percent water. While each company’s formula is a closely guarded secret, a review of the recognized 1,021 chemicals in these various proprietary mixes are known to include surfactants, biocides and even toxic substances like volatile organic compounds and carcinogens. As fracking has become more widespread in the 22 oil and gas shale plays throughout the United States, the proximity to major population centers has raised significant public health concerns as evidenced by conflict over development in the Marcellus Shale in the Northeastern United States. Of primary concern is the potentially damaging impact on water resources. Members of the public, some state and federal regulators and the environmental community have kept a close watch on the fracking process.
The Water Footprint of Fracking
Concern about the impact of fracking’s significant water use on local water resources, especially in dry lands, as well the potential for water pollution has led to a number of studies. Two recent studies from Duke University assessed the water footprint of the full life cycle (of each step) of the fracking process. The first study evaluated the median water use of six basins for shale-gas and shale oil and found that shale-gas water use ranged from 390,000 to 6.27 million gallons per well, while shale-oil use ranged from 70,000 to 2 million gallons of water per well.
Likewise, the second study reviewed six basins and charted the intensification of fracking’s water footprint, and found huge increases in both water use and wastewater in the years spanning 2011 to 2016. In that time, researchers found that water use per well rose by up to 770 percent while wastewater (flowback and produced water) volumes increased by a high of 1,440 percent within one year one of production.
Fracking Wastewater and Pathways to Pollution
There are many pathways to pollution from fracking. After the well is fracked and starts producing oil and gas, much of the fracking fluid remains underground where it could potentially contaminate groundwater if fractures connect to aquifer systems. There is some evidence that shallow aquifers have been polluted by methane either due to poorly constructed production wells, “communication” between production wells and drinking water wells, or both.
After the fracturing process, a percentage of the water returns fairly quickly to the surface as wastewater, also called “flowback.” The briny water that has long been underground and comes up during continued operation of the well, called “produced water,” can contain naturally occurring contaminants like the radioactive element radium, along with other heavy metals and salts. All of this wastewater is toxic and must be collected and stored; it then must be treated or discharged – or reinjected into a deep disposal well.
The wastewater is often pumped into holding ponds where it can leak and settle into surrounding groundwater, and impact wildlife. The contamination of groundwater is of major concern for those who live near drilling operations and rely on drinking water wells. And the contamination of watersheds that provide drinking water for millions of people in cities hundreds of miles away from any natural gas drilling sites poses a significant threat as well.
The US EPA’s “Assessment of the Potential Impacts of Hydraulic Fracturing for Oil and Gas on Drinking Water Resources” is the most comprehensive study to date on fracking. While the EPA claimed that fracking does not necessarily lead to “widespread, systemic” drinking water pollution, they did for the first time confirm that groundwater has been polluted at points along the fracking “water cycle.” The report also includes a major caveat that “[t]here is a high degree of uncertainty about whether the relatively few instances of impacts noted in this report are the result of a rarity of effects or a lack of data.”
Federal and state responses to the threats to water resources posed by fracking have been mixed at best. At the federal level, regulation is insufficient due to certain explicit exemptions from the Safe Drinking Water Act, the Clean Air Act, and the Clean Water Act granted by the Energy Policy Act of 2005.
The role that fracking will play in the United States’ energy future is quickly evolving. The nation is shifting towards increased oil and gas production and state governments are playing regulatory catch-up with the drilling technology’s rapid expansion to meet this burgeoning demand and export. As states debate how best to protect air and water resources from any potential fracking side effects, governments at all levels, scientists, public health experts, environmentalists and affected communities are engaged in the proper scope of research and oversight.
Image: Aerial view of fracking well pads. Credit: Simon Fraser University (Creative Commons).