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The fracking of oil and gas less than a mile from aquifers or the Earth’s surface now takes place across North America with few restrictions, posing increased risk for drinking water supplies, says a new Stanford study.
The study examined the frequency of so-called shallow fracking, described by the researchers as occurring less than a mile underground. Shallow fracking poses a greater risk to drinking water than fracking that occurs much deeper under the Earth’s surface.
Out of 44,000 wells fracked between 2010 and 2013 in the United States, researchers found that 6,900 (16 per cent) were fractured less than a mile from the surface and another 2,600 wells (six per cent) were fractured above 3,000 feet, or 900 metres.
"What surprised me is how often shallow fracturing occurs with large volumes of chemicals and water," said lead researcher and environmental scientist Robert Jackson in an interview with The Tyee.
The majority of shallow fracking now takes place in Texas, California, Arkansas and Wyoming. Although the study largely excludes Canada, shallow fracking also takes place in Saskatchewan, Alberta, Quebec, Manitoba and British Columbia, and sometimes at depths less than 500 metres.
Due to poor data reporting by industry and its regulators, "the occurrence of shallow hydraulic fracturing across the U.S. is underestimated in our analysis," added the study.
During shallow fractures, the industry injects fluids into vertical or horizontal wells to crack rock directly below or into groundwater. In many reported cases, the resulting fractures can travel up to 556 metres into other hydrocarbon zones, water formations or other energy well sites.
As a result, shallow fractures can connect to aquifers used for drinking water.
"Even fractures that do not extend all the way to an overlying aquifer can link formations by connecting them to natural faults, fissures or other pathways," explained the study.
Scientific studies have documented contamination of freshwater aquifers by fracking or fracking chemicals since 1984.
Fracking into water zones has been an issue for the technology since the 1950s.
Patents filed by industry repeatedly complain "it is not uncommon during hydraulic fracturing for the fracture to grow out of the zone of productive interest and proceed into a zone of non-productive interest, including zones containing water."
"There are more risks with shallow fracking," explained Jackson, because the separation between the zone being fracked and nearby aquifers is less, resulting in "the potential of directly connecting a fracture with an aquifer. It’s just common sense."
‘Greater potential risks’
Industry lobbyists, energy regulators and some scientific bodies have long argued that risks of groundwater contamination from fracking are minimal because the technology is pulverizing rock at such great depths (one to two miles underground) that any contact with groundwater or abandoned wells would be unlikely.
But the study found that deep fracking only accounted for three-quarters of new well drilling, and that industry was fracking rock in shallow zones near groundwater resources or even within drinking water resources throughout the U.S. Combined with little regulatory oversight, the practice posed "greater potential risks" for groundwater contamination.
Arkansas, for example, routinely fractures horizontal wells within a mile of the surface and with massive amounts of water and chemicals.
"The closer to the surface you frack, the greater the chance you will encounter an old well or a natural fissure or fracture," Jackson said. In addition, shallow frackers can "directly increase the change of stray gas migration" into groundwater or the atmosphere, he said.
Jackson thinks the risk is so significant that when the lateral segments of shallow horizontal wells stretch 600 to 900 metres underground, the groundwater above those laterals should be monitored, he said.
Usman Ahmed, vice-president of Baker Hughes, a major fracking service company, noted in a 2014 presentation that fracking technology is highly unpredictable because the cracks induced by industry will move in the path of least resistance.
As a consequence, 70 per cent of all well fractures don’t meet their target zones, 60 per cent of all fractures fail to release hydrocarbons and 73 per cent of all operators admit that "they do not know enough about the subsurface," reported Ahmed.
Prior to the shale gas revolution, the shallow fracturing of coal seams to extract methane resulted in hundreds of cases of groundwater contamination and gas migration inAustralia, New Mexico, Colorado, China, Alberta and Alabama.
Jackson found it surprising that "there are no limits on how shallow fracturing can be in the U.S. No state has an upward limit."
Nor does Canada: the Alberta Energy Regulator, which once described shallow fracking as "high risk" in a 2004 presentation, allows companies to perform high-volume frack jobs on wells shallower than 200 metres as long as they are located a short distance away from water wells.
In B.C., drillers can fracture zones at a depth of 600 metres but must get a permit to do so first.
In contrast, scientists at Durham University, U.K., recommend that "a minimum distance of 600 metres should be maintained between the fracture zone and an aquifer."
Fracking pollutes: EPA
Last June, the U.S. Environmental Protection Agency concluded in a 500-page draft report that fracking has polluted ground and surface water in cases ranging from Alberta to Pennsylvania.
"Some hydraulic fracturing operations are conducted within formations that contain drinking water resources," the report found, as did Jackson’s new study.
"In one field in Alberta, Canada, there is evidence that fracturing in the same formation as a drinking water resource (in combination with well integrity problems)… led to gas migration into water wells," said the EPA study.
According to the study, underground fracking operations have propelled fluids and gases out of the targeted areas "into underground drinking water resources," often through pre-existing fractures and pathways such as nearby abandoned or leaky wells.
In one example, the EPA reported that fracking had contaminated 25 per cent of 36 water wells in northeastern Pennsylvania, though the agency "did not find mechanisms have led to widespread, systemic impacts on drinking water resources in the United States."
In contrast, state agencies in Ohio, Pennsylvania, Texas and West Virginia have reported myriad problems, including hundreds of complaints about groundwater contamination due to fracking.
