Posted in | Pollution | Water

Fracking Affects Groundwater less than Oil and Gas Production

According to a new study, traditional techniques used for producing oil and gas can have an impact on groundwater much more than fracking. The study was performed by hydrogeologists Grant Ferguson from the University of Saskatchewan and Jennifer McIntosh from the University of Arizona.

Oil and gas well with brine separator tank in the background in southern Ontario, Canada. (Image credit: Jennifer McIntosh)

Fracking can be described as high-volume hydraulic fracturing in which chemicals, sand, and water are injected into petroleum-bearing rock formations under high pressure to recover formerly inaccessible oil and natural gas. This technique was responsible for the present shale gas boom that began approximately 15 years ago.

Traditional techniques of oil and natural gas production have been used since the late 1800s. Similar to fracking, these methods also involve injecting water underground to help recover oil and natural gas.

If we want to look at the environmental impacts of oil and gas production, we should look at the impacts of all oil and gas production activities, not just hydraulic fracturing.

Jennifer McIntosh, Professor of Hydrology and Atmospheric Sciences, University of Arizona

The amount of water injected and produced for conventional oil and gas production exceeds that associated with fracking and unconventional oil and gas production by well over a factor of 10,” she stated.

Both Ferguson and McIntosh looked at the amount of water that was injected and is being injected underground through petroleum industry activities. They also looked at how those activities alter pressures and the movement of water underground, and how those practices are likely to pollute groundwater supplies.

While the use of groundwater differs from one region to another, approximately 30% of Canadians and over 45% of Americans rely on this resource for their agricultural, domestic and municipal requirements. Surface freshwater supplies in more arid regions of Canada and the United States are equally significant.

According to McIntosh and Ferguson, the petroleum-bearing rock formations may currently contain more water than initially believed due to conventional production activities.

The traditional technique, called enhanced oil recovery, pushes the oil and gas toward extraction wells by injecting water into petroleum-bearing rock formations. This process produces saline water as a by-product which is subsequently re-injected, along with extra freshwater, in order to extract more amounts of oil and gas.

Conversely, towards the end of the cycle, the surplus salt water is discarded by injecting it deep into geological formations or depleted oil fields devoid of oil and gas. However, that injection of waste water has altered the behavior of underground liquids and also raises the possibility of polluted water reaching freshwater aquifers.

Freshwater from shallow aquifers or from the surface was some of the water injected as part of oil and gas production activities. According to McIntosh, that approach can possibly impact surface water and groundwater supplies in water-stressed regions, like Texas or New Mexico.

There's a critical need for long-term—years to decades—monitoring for potential contamination of drinking water resources not only from fracking, but also from conventional oil and gas production.

Jennifer McIntosh, Professor of Hydrology and Atmospheric Sciences, University of Arizona

The researchers published their paper, titled “Conventional Oil—The Forgotten Part of the Water-Energy Nexus,” online on June 30th, 2019 in the journal Groundwater. The study was funded by Global Water Futures.

McIntosh has been part of studies relating to the environmental impacts of hydraulic fracturing. She started to speculate how such environmental impacts compare to the impacts of the traditional techniques of oil and gas production—techniques that have been employed for approximately 120 years and are still being used.

Surface water and groundwater are used by both fracking and traditional practices when sufficient water is not available from other sources to continue the production of petroleum.

McIntosh and Ferguson eventually generated data from a wide range of sources to see how all kinds of oil and gas production activities impacted water use in the United States and Canada. Moreover, the available published scientific studies did not cover all the regions. Therefore, the researchers also checked reports available from state agencies and other sources of data.

They found information for the Permian Basin (located in Texas and New Mexico), the Western Canada Sedimentary Basin, the states of Ohio, Oklahoma, and California, and the overall amount of water generated by high-volume hydraulic fracturing across the United States.

What was surprising was the amount of water that's being produced and re-injected by conventional oil and gas production compared to hydraulic fracturing,” McIntosh stated. “In most of the locations we looked at—California was the exception—there is more water now in the subsurface than before. There’s a net gain of saline water.”

There are regulations that control the petroleum sectors with respect to groundwater, but data about what is occurring underground differs by state and province. While some jurisdictions keep exceptional data, for others it is almost nonexistent. In spite of this, Ferguson claimed that he and McIntosh can make certain observations.

I think the general conclusions about water use and potential for contamination are correct, but the details are fuzzy in some areas. Alberta probably has better records than most areas, and the Alberta Energy Regulator has produced similar numbers to ours for that region. We saw similar trends for other oil and gas producing regions, but we need better reporting, record keeping and monitoring.

Grant Ferguson, Hydrogeologist, University of Saskatchewan

Environmental impacts of oil and gas production activities are far from petroleum-producing areas. For instance, earlier studies demonstrated that detectable seismic activity can occur over 90 km away when disposal wells are operated. Traditional activities inject water at lower volumes and at lower pressure, but occur over longer durations of time, which may lead to contamination over greater distances.

Moreover, thousands of dormant, active, and abandoned wells are spread across North America which is another wild card. Some were not properly decommissioned or leaky, offering potential pathways for contamination of freshwater aquifers.

Although some efforts are being made to address this issue via organizations like Alberta’s Orphan Well Association, there is not much consensus regarding the extent of the problem. Ferguson stated that based on the type of source cited, the decommissioning price tag ranges between a few billion and a few hundred billion dollars.

Canada’s C.D. Howe Institute published a report in 2017 which indicated that Alberta contains 155,000 wells that have not been remediated yet. According to a 2014 paper published by other investigators, there are at least 300,000 abandoned wells in Pennsylvania alone, and many of these are “lost” because records are not available of their existence and also surface evidence is not available to indicate that an oil well was once present there.

We haven't done enough site investigations and monitoring of groundwater to know what the liability really looks like,” Ferguson said. “My guess is that some wells probably should be left as is and others are going to need more work to address migration of brines and hydrocarbons from leaks that are decades old.”

Source: https://www.arizona.edu/

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