Environmental Considerations of Shale and Tight Resource Development
Opposition to shale and tight resource development usually centres on the potential impacts of hydraulic fracturing on public health and the environment.
Common environmental concerns relate to the potential impacts of development on surface water and groundwater sources, and air emissions. Potential land impacts including earthquakes (or induced seismicity) have also gained public attention.
In 2013, Environment Canada commissioned the Council of Canadian Academies to conduct a study on the state of knowledge of the environmental impacts associated with shale gas development in Canada. The report concluded that there are gaps in the scientific knowledge with respect to water resources and air emissions (both of which relate to well integrity), land, induced seismicity and societal impacts.
There is ongoing federal research to evaluate exploration or production techniques to prevent or minimize the risks of contamination, emissions, land impacts and induced seismicity associated with shale and tight resource development.
Water Quality and Quantity
The risk of surface and groundwater contamination from shale and tight resource exploration and production, and hydraulic fracturing in particular, is a common concern, particularly in populated areas where surface and groundwater is used as drinking water or for agricultural or industrial purposes.
Hydraulic fracturing has been used to stimulate production wells for conventional oil and natural gas reservoirs in North America for more than 60 years. Over 180,000 wells have been hydraulically fractured in Alberta alone (mostly vertical wells). About 14,000 horizontal wells have been hydraulically fractured so far across Canada, with most of them located in relatively remote areas. The majority involved relatively large, high volume fracture treatments.
Regulation of the oil and gas sector in Canada is designed to protect water resources during oil and gas development, including shale and tight development. Specific regulations vary between jurisdictions, but in all cases steel casing and cement are used to isolate and protect groundwater zones from deeper oil, natural gas and saline water zones.
Generally, all wastewater from hydraulic fracturing operations is collected and stored in enclosed tanks or impoundments with secondary containment to avoid potential soil infiltration. This wastewater can then be reused in other fracking operations or reinjected at depth in deep saline aquifers. Wastewater is not introduced into surface waters (e.g., lakes and streams) or into near surface aquifers used for potable water supply.
What chemicals are used in in hydraulic fracturing fluids?
During hydraulic fracturing, chemical additives (generally representing less than 1 percent of the fluid injected) are used for several purposes, mostly to increase the viscosity of the injected fluid, optimize post-fracturing water recovery or protect the production pipe casing from corrosion. The fracturing fluid used is specific to each operator and differs from one formation to another.
The chemical registry FracFocus.ca provides information related to additives used in hydraulic fracturing operations, methods of fracking and provincial regulations. Companies in British Columbia, Alberta and New Brunswick have a legal obligation to publicly disclose additives used in their fracturing fluids, and those regulated by the Canada Energy Regulator (formerly the National Energy Board) have a similar requirement.
Besides water quality issues, there is also public concern related to water quantity requirements for shale and tight resource development.
Not all unconventional reservoirs require large amounts of water and high pressure to frack. The quantity of water required to stimulate a well depends mainly on the geology and rock properties of the reservoir, which determine the pressure, depth, length, and method of stimulation necessary to fracture the rock.
While industry has historically used slickwater in hydraulic fracturing operations (a mix of water, sand and chemical additives), other techniques include using foams (a mix of gas and water), liquid propane, nitrogen, carbon dioxide, and combinations of these methods.
Another environmental concern related to shale and tight resource development relates to atmospheric emissions and air quality. Air contaminants, toxins and greenhouse gases can have impacts on population and ecosystem health on a regional scale, and on climate change on a global scale.
Most shale and tight gas plays currently being developed have low carbon dioxide content, similar to typical conventional gas production. Therefore, the greenhouse gas emissions per unit of shale and tight gas produced and consumed are similar to those from conventional natural gas production and use.
Does shale gas produce more greenhouse gas emissions than conventional gas? What about coal or petroleum products?
Lifecycle analysis considers all significant greenhouse gas emissions from all stages of production, processing, transportation and end-use of a fuel to provide a complete carbon footprint. Natural Resources Canada’s GHGenius lifecycle analysis tool was used to model the greenhouse gas emissions of shale gas.
Overall, this research found that shale gas had slightly higher emissions than conventional natural gas (4 percent higher) but had much lower emissions (29 percent to 38 percent lower) than petroleum products or coal.
Whenever natural gas is produced and cannot be marketed or re-injected into an oil or gas well, it must be either vented or flared.
Some studies assert that large volumes of methane, a potent greenhouse gas that is the main component of natural gas, are vented to the atmosphere during shale or tight well construction. This is rare in Canada due to environmental, economic and safety considerations. Most provinces that have significant natural gas production also have initiatives to reduce venting and flaring of gas.
Environment and Climate Change Canada’s greenhouse gas reporting program is for large facilities only. Hydraulic fracturing activities do not meet the threshold for reporting emissions, and most emission sources would occur at facilities not subject to reporting.
While provincial regulators set requirements and regulations for greenhouse gas emissions, these do not typically include small sources.
Methane leakage from wellbores has also been identified as a potential cause for atmospheric contamination (fugitive emissions) from both conventional and unconventional wells. In Western Canada, provincial monitoring requirements enable regulators to quantify fugitive emissions that come directly from the well.
Common concerns related to potential land impacts of shale and tight development are footprint and induced seismicity.
The land-use footprint of shale and tight development is not expected to be much more than the footprint of conventional operations. Advances in horizontal drilling technology allow for many wells to be drilled and produced from the same site. With the use of well pads, where multiple horizontal wells are drilled from the same location, fewer access roads are required and the concentration of facilities and pipelines within the footprint further minimizes surface disturbance.
Most natural earthquakes in Canada occur in active seismic zones where hydraulic fracturing or deep-well wastewater injection is not taking place.
While hydraulic fracturing or deep wastewater injection can sometimes be linked to the occurrence of felt earthquakes, these events are usually relatively minor and rarely felt.
How does Natural Resources Canada monitor earthquakes and study induced seismicity?
Across Canada, there are more than 200 seismographs continuously recording local and global earthquake activity. Dense arrays of seismographs have been installed locally in several areas with hydraulic fracturing operations (e.g., northeast British Columbia) to decipher the source of tremors and to understand the rock reaction to hydraulic fracturing parameters.
In the case of areas with shale and tight reservoir development, the issue is to distinguish deep crustal events from shallow events linked either to fracking programs or to wastewater reinjection in deep aquifers.
Arrays of seismographs have also been deployed in the Northwest Territories and New Brunswick in areas of potential shale and tight reservoir exploration and development to monitor the regions’ natural seismicity as a baseline.
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