Human activities, such as greenhouse gas emissions and deforestation, have a well-documented impact on Earth’s surface. However, a team of hydrology researchers from the University of Arizona has conducted a study to explore how these activities also influence Earth’s deep subsurface, a zone that lies hundreds of meters to several kilometers beneath the surface. The study, published in the journal Earth’s Future, looked at how human activities, such as oil and gas production, geothermal energy production, geologic carbon sequestration, and lithium extraction, impact the circulation of fluids in the deep subsurface.
The researchers found that human-induced fluid fluxes are projected to increase with proposed strategies for climate change mitigation. These strategies include geologic carbon sequestration, geothermal energy production, and lithium extraction from underground brine. Responsible management of the subsurface is crucial for a sustainable future and to keep warming below a few degrees, according to the study’s co-author, Peter Reiners, a professor in the UArizona Department of Geosciences. The study was conducted in collaboration with researchers from various institutions across the globe.
Oil and natural gas production involve the extraction of water, typically saline, from the deep subsurface, which is then blended with water from near-surface sources and reinjected into the subsurface. This process is repeated to maintain reservoir pressures and facilitate efficient oil recovery. The same cycle occurs in operations like lithium extraction, geothermal energy production, and geologic carbon sequestration, where saline water is reinjected into the deep subsurface. The study found that the fluid injection rates from human activities are greater than what naturally occurs in the deep subsurface.
As human activities like carbon capture and sequestration and lithium extraction increase, the researchers predicted that these activities might be recorded in the geological record. Additionally, human activities have the potential to alter the microbial communities that live in the deep subsurface. For example, hydraulic fracturing, a technique used in oil and gas extraction, can lead to a sudden increase in microbial activity in deep rock formations. There are still many unknowns about how human activities impact Earth’s deep subsurface, and it is essential to continue studying these questions for a better understanding of the subsurface environment.
The researchers emphasized the importance of using the deep subsurface as part of the solution for the climate crisis. Despite its vital role in Earth’s ecosystem, much is still unknown about the deep subsurface. The study highlights the need for further research to understand and mitigate the impact of human activities on the deep subsurface. As Jennifer McIntosh, the senior author of the study, pointed out, there is more information available about the surface of Mars than there is about the water, rocks, and life deep beneath our feet. Understanding and managing the deep subsurface is crucial for a sustainable future and combating climate change.
