"This research effort will provide valuable insight into both the requirements of the instrumentation necessary to ensure the safe storage of CO2 underground, and the geological formations that are expected to permanently store greenhouse gas in the Southeast United States," the Energy Department said in a statement.

The project began July 15 at a depth of 10,300 feet, officials said, noting the injected gas is naturally occurring CO2 trapped in the subsurface formation known as the Jackson Dome, said Denbury Resources Inc. (NYSE:DNR) of Plano, Texas, the project's host.

The CO2 will be injected at the rate of 250,000 to 500,000 metric tons annually during the next several years.

"Carbon capture and sequestration of CO2 is not a future technology, but is actually occurring today in CO2 enhanced recovery projects such as the Cranfield field," said Denbury Senior Vice President Tracy Evans. "Sequestration of CO2 in enhanced oil recovery projects will provide the bridge to full scale carbon capture and storage of CO2 and can be expanded today, versus waiting for another five or 10 years to pass."