Tucson Standard

Researchers from the University of Arizona have conducted a study on the impact of human activities on Earth's deep subsurface. The study, published in the journal Earth's Future, examines how activities such as oil and gas production affect fluid circulation beneath the planet's surface.

Jennifer McIntosh, a professor in the UArizona Department of Hydrology and Atmospheric Sciences, explained, "We looked at how the rates of fluid production with oil and gas compare to natural background circulation of water and showed how humans have made a big impact on the circulation of fluids in the subsurface."

Lead author Grant Ferguson emphasized the importance of understanding these impacts: "The deep subsurface is out of sight and out of mind for most people, and we thought it was important to provide some context to these proposed activities, especially when it comes to our environmental impacts."

The study projects that human-induced fluid fluxes will increase with climate change strategies like geologic carbon sequestration, geothermal energy production, and lithium extraction. These processes involve reinjecting saline water into the subsurface.

Peter Reiners, a co-author from UArizona's Department of Geosciences, stated, "Responsible management of the subsurface is central to any hope for a green transition, sustainable future and keeping warming below a few degrees."

McIntosh noted that oil and natural gas production involves cycling saline water through deep subsurface layers. This process is also used in lithium extraction and geothermal energy production. She highlighted that "the fluid injection rates or recharge rates from those oil and gas activities is greater than what naturally occurs."

Using data from various sources, researchers found that current human-induced fluid movement rates exceed natural levels. They also explored potential geological records left by activities like carbon capture.

Human activities could alter microbial environments in the deep subsurface. Hydraulic fracturing might introduce new microbial communities or change existing ones.

McIntosh stressed ongoing research: "There remain a lot of unknowns about Earth's deep subsurface and how it is impacted by human activities." She concluded by saying, "We need to use the deep subsurface as part of the solution for the climate crisis."