The Arizona Geological Survey at the University of Arizona is leading a $12 million feasibility study to explore carbon dioxide storage in the deep subsurface of the Harquahala basin, approximately 60 miles west of Phoenix.

Natural gases and liquid petroleum gas have been safely stored underground for decades in many locations around the world. Similarly, carbon dioxide emissions from power plants or other sources can be captured, compressed and injected into deep saline reservoirs to mitigate the effects of excess carbon dioxide in the atmosphere. 

The feasibility study, funded by the Department of Energy's National Energy Technology Laboratory, is part of a broader national effort to characterize geologic locations suitable for carbon dioxide storage in the United States. 

Set to begin in March, the CarbonSAFE II project could lead to a reduction of Arizona's overall carbon emissions by 25% in the next 40 years.

The project brings together experts from the U of A, the New Mexico Institute of Mining and Technology, the University of Utah, and Los Alamos National Laboratory, with the U of A receiving $9 million of the funding. Their research will examine sedimentary and volcanic rocks in the Harquahala basin, which shows promising characteristics for carbon dioxide storage. The Arizona Geological Survey – based at the U of A – will lead the project's technical evaluation and data integration efforts, and the university's Office of Societal Impact will evaluate community impacts and benefits.

The U of A researchers believe that rocks more than 5,000 feet beneath the ground have suitable permeability and porosity for carbon dioxide storage The team's selection of the Harquahala basin site was informed by a pre-feasibility study completed earlier this year, which indicated the basin's potential for carbon storage. 

"This particular location is advantageous due to multiple factors," said Tawnya Wilson, a research scientist at the Arizona Geological Survey, who is serving as project co-principal investigator alongside principal investigator Brian Gootee, senior research geologist at the Arizona Geological Survey. 

"There are promising rock formations at depth," Wilson said. "The storage site is in close proximity to nearby power generating stations that emit carbon dioxide. There is access to the Interstate I-10 transportation corridor with existing pipeline infrastructure. There is likely a large volume of saline groundwater, and there is a very low risk of earthquakes." 

 The project builds upon nearly 15 years of carbon sequestration research at the Arizona Geological Survey, including participation in previous Department of Energy regional initiatives. Recently, the project team conducted preliminary research through the Carbon Utilization and Storage Partnership, a multistate coalition involving three national laboratories, geological surveys and universities across 14 Western states.

The CarbonSAFE II project will use well drilling and advanced geological investigation methods, including 2D seismic imaging – a technology that uses sound waves to create detailed pictures of underground rock layers – to assess the basin's carbon dioxide storage potential and build a 3D geological reservoir model to track the size and position of the carbon dioxide plume over time. The project will also examine potential risks of underground storage in the area. 

"This comprehensive data collection will help us determine if this site is suitable for long-term carbon storage and support our efforts to meet the government's 2050 carbon emission reduction goals," Wilson said. 

Based on the existing carbon dioxide source emitters nearby, about 50 million metric tons of carbon dioxide could be captured and stored over 30 years. This would reduce Arizona's carbon emissions by 25% over that time period, Wilson said.