Water-intensive method of extracting natural gas has some concerned
Posted: Apr 27, 2011 5:48 PM ET
Last Updated: Apr 27, 2011 5:55 PM ET
What is it?
Hydraulic fracturing, or "hydro-fracking," is a form of natural gas extraction in which a pressurized mix of water and other substances is injected into shale rock formations or coal beds to release trapped natural gas. A fluid mixture of water and chemicals is injected under high pressure deep underground, creating or widening fissures in the rock. Then, sand or another solid, often ceramic beads, is pumped in to keep the fissures propped open so that methane gas can escape from pores and fractures in the rock.
The technique can also be used to extract oil and geothermal energy.
How deep are the wells?
Hydro-fracking wells can be drilled vertically, vertically and horizontally or directionally, i.e. on a slant. According to the U.S. Environmental Protection Agency (EPA), wells can be anywhere from 300 metres to 2.5 kilometres deep and extend for hundreds of metres horizontally from the well site.
How much water is used?
The EPA estimates one well in a coal bed can require anywhere from 200,000 litres to more than 1 million litres while a horizontal well in a shale formation can use between 7.5 million to 19 million litres of water
How is the water disposed of?
The amount of water recovered after hydro-fracking varies widely depending on the drill site. The EPA estimates anywhere from 15 to 80 per cent of water is recovered. There are several ways of disposing of the water used in the process. It can be stored underground in impermeable injection wells that prevent it from leaking into the environment or in steel tanks or pits; recycled for use in another fracturing well; or treated and discharged back into the water supply. Because of its high salt content, the waste water is often also bought by municipalities for use in de-icing and dust suppression on roads.
What chemicals are used?
Although the fluid used in fracking is mostly water, some acids, emulsifiers and other chemicals are added to make the water more viscous and effective at fracturing the rock. These include guar gum, boron, zirconium, titanium, iron and polyacrylamide.
Aside from such additives, the process of fracking also releases naturally occurring salts, metals, radioactive elements like barium and strontium and carcinogens like benzene.
What are the environmental concerns?
- Water use: the process uses large amounts of fresh or potable water.
- Waste disposal: space is needed to store the waste water safely; sometimes, this involves clearing trees or disrupting habitats. The waste water must be treated at facilities that critics say are not always equipped to remove the contaminants particular to hydro-fracking.
- Contamination: the fear is that the chemicals used and released during fracking contaminate drinking- and groundwater — either during the process itself or through the waste water that is recycled and used afterward. The substances released along with the natural gas can continuing leaking from the well for decades after the extraction process.
- Air pollution: some of the methane gas being extracted during fracking escapes or is vented at the well head during the process and contributes to greenhouse gas emissions. In addition, some people living near fracking wells have complained of noxious fumes that they say cause headaches, nausea and other symptoms and that they attribute to some of the substances released during fracking, such as benzene and toluene. The New York Times reported that parts of Texas where hydro-fracking is common have seen higher rates of asthma although these could not be directly attributed to the industry as the areas had high air pollution generally.
Researchers at Cornell University have recently concluded that shale gas extraction through fracking causes enough emissions to give it a bigger greenhouse gas footprint than conventional gas or oil. The EPA is currently conducting an analysis of the health and environmental risks associated with hydro-fracking and expects to release preliminary results in late 2012.
What does the industry say?
The industry stresses that hydro-fracking does not contaminate drinking water because it occurs hundreds of metres below the water table and is buffered by billions of tons of impermeable rock. It says the chemicals used in the process are common materials that pose no significant risk to human health and that the amounts of other substances released during extraction, such as benzene, do not exceed the levels considered safe. It says it stores waste water in accordance with environmental regulations and recycles flowback water where possible.
Why is water lighting on fire?
There have been reports of people living near fracking facilities being able to set their tap water on fire. Some have seen this as evidence that the waste water from the natural gas wells has not been adequately treated and contaminants have been allowed to pollute the water supply. The industry and some environmental groups have said that what is catching fire in these instances is naturally occurring methane gas that has dissolved in well water and is not harmful or related to gas extraction.
How common is hydro-fracking?
The technique has been around since the 1950s, but its use has grown significantly in the past few years as demand for cleaner energy has increased and technologies for extracting natural gas have improved. According to the Canadian Society for Unconventional Gas and other industry sources, the advent of horizontal drilling has increased the volume that can be extracted from what are considered unconventional reserves such as so-called tight reservoirs, coal beds and shale deposits. This, they say, has potentially extended the natural gas supply by more than 100 years.
There are hydro-fracking wells in western and eastern Canada, with Alberta accounting for most of the country's natural gas production thanks to the Western Canada Sedimentary Basin that runs through the province. Quebec has recently imposed a moratorium on new hydro-fracking wells while it does an environmental assessment of the practice. Soon after, New Brunswick announced it would go ahead with shale gas exploration, but officials said wells would not be up and running for at least another two years. Nova Scotia is also reviewing the practice.
In the U.S., the EPA estimates that by 2020, shale gas will account for 20 per cent of the country’s total gas supply. Hydro-fracking has been of particular concern in Pennsylvania, which has a large shale deposit known as the Marcellus Shale and, according to an extensive New York Times investigation, has seen the number of natural gas wells grow from about 36,000 to 71,000 between 2000 and 2011. New York state has imposed a moratorium on new fracking wells until July 2011.
How is hydro-fracking regulated?
In Canada, hydro-fracking is regulated provincially under the same laws that govern the oil and gas industry generally. The main regulations have to do with how close to the surface wells can be drilled and what testing must be done on waste water. In Alberta, fracturing operations must be 200 metres or deeper underground, for example.
Critics say existing laws do not deal specifically enough with the unique challenges posed by the explosive growth of hydro-fracking and that testing and tracking of the waste from the extraction process should not be left up to the industry.
Environmentalists and others opposed to hydro-fracking would like to see a moratorium imposed on the practice until tighter regulations are adopted or at least a ban on hydro-fracking near groundwater well sites, residential areas and livestock operations. They would also like companies to be compelled to release the results of their water testing to the public.
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