Human Activities have a Big Impact on Deep Subsurface Fluid Flow

The effects of human activities, including greenhouse gas emissions and deforestation, on Earth’s surface have been extensively researched. Recently, hydrology experts from the University of Arizona delved into the influence of human actions on the deep subsurface of the Earth, an area located hundreds of meters to several kilometers below the surface.

“We examined the disparity between fluid production rates from oil and gas activities and the natural circulation of water, demonstrating the significant human impact on subsurface fluid circulation,” explained Jennifer McIntosh, a professor at the University of Arizona’s Department of Hydrology and Atmospheric Sciences and the senior author of a paper published in the journal Earth’s Future, outlining these discoveries.

Grant Ferguson, the lead author of the study and an adjunct professor at the University of Arizona’s Department of Hydrology and Atmospheric Sciences, as well as a professor at the University of Saskatchewan’s School of Environment and Sustainability, emphasized the importance of shedding light on the deep subsurface, often overlooked by many.

“It’s crucial to provide context for these proposed activities, particularly regarding their environmental consequences,” he stated.

Projected Rise in Human-Induced Fluid Fluxes due to Climate Change Mitigation Strategies

The study anticipates that human-induced fluid fluxes will escalate in the future due to proposed climate change mitigation strategies. These strategies include geologic carbon sequestration, geothermal energy production, and lithium extraction from underground brine for electric vehicle power.

The research involved collaboration with scholars from the University of Saskatchewan, Harvard University, Northwestern University, the Korea Institute of Geosciences and Mineral Resources, and Linnaeus University in Sweden.

“Responsible management of the subsurface is crucial for envisioning a transition to a sustainable future and mitigating climate change impacts,” emphasized Peter Reiners, a professor at the University of Arizona’s Department of Geosciences and one of the study’s co-authors.

Jennifer McIntosh, also from the University of Arizona, highlighted that saline water from the deep subsurface, often millions of years old, typically accompanies hydrocarbons to the surface during oil and natural gas extraction.

Continuous Cycle of Saline Water Reinjection in Subsurface Fluid Management

Water, which accumulates salinity through ancient seawater evaporation or interactions with rocks and minerals, blends with additional near-surface water for enhanced oil recovery and reservoir pressure maintenance. This blending results in the creation of a saline solution, which humans reinject into the subsurface, thus establishing a continuous cycle of fluid production and reinjection.

Similar processes in lithium extraction, geothermal energy production, and geologic carbon sequestration involve reinjecting saline water leftover from underground operations.

McIntosh explained, “We’ve demonstrated that the rates of fluid injection or recharge from these oil and gas activities exceed natural rates.”

By analyzing existing data, including fluid movement measurements associated with oil and gas extraction and water injections for geothermal energy, the researchers concluded that current human-induced fluid movement rates surpass those occurring naturally.

Furthermore, the study predicts how intensifying human endeavors such as carbon capture and sequestration and lithium extraction might be reflected in the geological record.

Potential Impacts of Human Activities on Deep Subsurface Fluid Dynamics and Microbial Communities

These activities could potentially not only alter deep subsurface fluid dynamics but also impact microbial communities residing therein, either through changes in water chemistry or the introduction of surface-dwelling microbes.

For instance, hydraulic fracturing, a method used to extract oil and gas by fracturing underground rocks with pressurized liquids, may prompt sudden microbial proliferation in previously dormant deep rock formations.

Despite advancements, numerous uncertainties persist regarding Earth’s deep subsurface and its interactions with human activities.

McIntosh emphasized the importance of further research in this area, stating, “We must leverage the deep subsurface as part of our climate crisis solution. Yet, our understanding of the water, rocks, and life deep beneath our feet lags behind our knowledge of the surface of Mars.”

Read the original article on: Phys org

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