Fracturing has less impact on groundwater than traditional oil and gas production

According to hydrogeologists Jennifer McIntosh of the University of Arizona and Grant Ferguson of the University of Saskatchewan, conventional oil and gas production methods can affect groundwater much more than fracking .

High-volume hydraulic fracturing, known as fracking, involves injecting water, sand and chemicals under high pressure into oil rock formations to recover previously inaccessible oil and natural gas. This method has led to the current shale gas boom that began about 15 years ago.

Conventional oil and gas production methods, which have been in use since the late 19th century, also inject water underground to help recover oil and natural gas.

"If we want to look at the environmental impacts of oil and gas production, we need to look at the impacts of all oil and gas production activities, not just hydraulic fracturing," said McIntosh, a professor of oil and gas production. Hydrology and Atmospheric Sciences at the University of Arizona.

"The amount of water injected and produced for conventional oil and gas production exceeds by more than a factor of 10 that associated with fracking and the production of unconventional oil and gas," she declared.

McIntosh and Ferguson examined the amount of injected and underground water injected into the subsoil by the activities of the oil industry, how these activities changed groundwater pressures and movements and in what these practices could contaminate groundwater reserves.

Although groundwater use varies by region, approximately 30% of Canadians and more than 45% of Americans depend on the resource for their municipal, domestic and agricultural needs. In the more arid regions of the United States and Canada, surface freshwater supplies are equally important.

McIntosh and Ferguson discovered that there was probably more water in the oil formations than initially because of traditional production activities.

To push oil and gas to the extraction wells, the traditional method, called enhanced oil recovery, involves injecting water into rock formations containing oil. Saline water is produced as a by-product and is then reinjected with additional freshwater to extract more oil and gas.

However, at the end of the cycle, excess salt water is removed by injecting it into depleted oil fields or deep into geological formations containing neither oil nor gas. This wastewater injection has changed the behavior of liquids underground and increases the risk of contamination of water contaminated by freshwater aquifers.

Some of the water injected in oil and gas production activities comes from shallow surface waters or shallow aquifers. McIntosh said this could affect groundwater and surface water supplies in areas of water stress such as New Mexico or Texas.

"It is imperative to monitor for years – if not decades – the potential contamination of drinking water resources, not only through fracking, but also through the production of conventional oil and gas," said McIntosh. .

The team published its article "Conventional Oil – The Forgotten Part of the Water-Energy Link", online in the newspaper Groundwater. Global Water Futures funded the research.

McIntosh has been involved in studies of the environmental impacts of hydraulic fracturing. It began to ask how these impacts compare to those of conventional oil and gas production methods, which have been in use for about 120 years and continue to be so.

Fracturing and conventional practices use groundwater and surface water when there is not enough water from other sources to continue oil production.

To see how all types of oil and gas production activities have affected water use in Canada and the United States, she and Ferguson have synthesized data from a variety of sources. Available published scientific studies covered only a few regions. Therefore, scientists have also delved into the reports of state agencies and other sources of information.

Researchers found information on the Western Canadian Sedimentary Basin, the Permian Basin (located in New Mexico and Texas), the Oklahoma, California and Ohio states, as well as the total amount of water produced by high volume hydraulic fracturing in the United States.

"What was amazing was the amount of water produced and reinjected by conventional oil and gas production compared to hydraulic fracturing," McIntosh said. "In most places we've looked at, with the exception of California, there's more water in the basement than before." ;salt water."

The petroleum industry is subject to groundwater regulations, but information on underground activities varies by province and state. Some jurisdictions maintain excellent data, while for others, they are virtually non-existent. Despite this, Ferguson said he and McIntosh could make a few observations.

"I think the general conclusions about water use and the potential for contamination are correct, but the details are unclear in some areas," Ferguson said. "Alberta probably has better records than most regions, and the Alberta Energy Regulator has produced similar numbers to ours for this region, and we've seen similar trends in other oil-producing regions as well." gas, but we need better systems for reporting, record keeping and monitoring. "

Oil and gas production activities can have environmental effects away from oil-producing regions. For example, previous studies show that the operation of evacuation wells can cause seismic activity detectable at more than 90 kilometers. Conventional activities inject lower volumes of water at lower pressures, but take place over longer periods, which can lead to contamination over longer distances.

The thousands of active, dormant and abandoned wells in North America are another asset. Some have leaked or been inappropriately downgraded, providing potential pathways for freshwater aquifers.

While efforts are being made to address this issue through organizations such as the Orphan Well Association of Alberta, there is little consensus on the extent of the problem. According to Ferguson, the price of decommissioning varies from a few billion to a few hundred billion dollars, according to the source cited.

A 2017 report of the Canadian CD. The Howe Institute says there are still 155,000 wells in Alberta to restore. An article published in 2014 by other researchers suggests that Pennsylvania alone has at least 300,000 abandoned wells, many of which are "lost" because there is no record of their existence and there is no reason to believe that there are any. There is no superficial evidence of the presence of an oil well.

"We have not done enough on-site surveys and groundwater monitoring to find out what the liability really looks like," Ferguson said. "I suppose some wells should probably be left as they are and others will need more work to address the decades-old migration of brine and oil from leaks."