According to hydrogeologists Jennifer McIntosh from the University of Arizona and Grant Ferguson from the University of Saskatchewan, conventional oil and gas production methods can affect groundwater much more than fracking. They found that the amount of water injected and produced for conventional oil and gas production is more than that associated with fracking and unconventional oil and gas production by more than a factor of 10. The researchers looked at how petroleum industry activities inject water underground, how those activities change pressures and water movement underground, and how those practices could contaminate groundwater supplies.
What is Fracking?
Fracking is the process of injecting water, sand, and chemicals under high pressure into petroleum-bearing rock formations to recover previously inaccessible oil and natural gas. This method led to the current shale gas boom that started about 15 years ago.
Conventional Methods of Oil and Natural Gas Production
Conventional methods of oil and natural gas production have been in use since the late 1800s, and they also inject water underground to aid in the recovery of oil and natural gas. To push the oil and gas toward extraction wells, the conventional method, known as enhanced oil recovery, injects water into petroleum-bearing rock formations. Saline water is produced as a by-product and is then re-injected, along with additional freshwater, to extract more oil and gas. However, at the end of the cycle, the excess salt water is disposed of by injecting it into depleted oil fields or deep into geological formations that don’t contain oil and gas. That injection of waste water has changed the behavior of liquids underground and increases the likelihood of contaminated water reaching freshwater aquifers.
Impact of Oil and Gas Production on Groundwater Supplies
Groundwater use varies by region, but about 30% of Canadians and more than 45% of Americans depend on the resource for their municipal, domestic, and agricultural needs. In more arid regions of the United States and Canada, surface freshwater supplies are similarly important. Some of the water injected as part of oil and gas production activities is freshwater from the surface or from shallow aquifers. This could affect groundwater and surface water supplies in water-stressed regions such as New Mexico or Texas.
Long-Term Monitoring of Drinking Water Resources
There’s a critical need for long-term monitoring for potential contamination of drinking water resources not only from fracking, but also from conventional oil and gas production. Despite the regulations governing the petroleum industry with regard to groundwater, information about what is happening underground varies by province and state. There are also thousands of active, dormant, and abandoned wells across North America that could cause contamination of freshwater aquifers.
While there is some effort to deal with this problem through organizations such as Alberta’s Orphan Well Association, there is little consensus as to the size of the problem. The researchers concluded that there is a need for better reporting, record keeping, and monitoring in order to minimize the environmental impact of oil and gas production activities.
A 2017 report from Canada’s C.D. Howe Institute indicates that there are 155,000 wells in Alberta yet to be remediated. A 2014 paper by other researchers suggest Pennsylvania alone has at least 300,000 abandoned wells, many of which are “lost” because there are no records of their existence nor is there surface evidence that an oil well was once 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.”