ADM CCS project takes another step forward

By Erin Voegele | March 16, 2010
Posted April 8, 2010

Archer Daniels Midland Co.'s Decatur, Ill.-based carbon capture and storage (CCS) project at its ethanol plant has moved one step closer to fruition with the recent completion of a 3-D seismic survey. The survey, which is essential in determining the geometry and internal structure of the saline reservoir that carbon dioxide (CO2) will be injected into, was completed by the Midwest Geological Sequestration Consortium. MGSC is one of seven regional partnerships created by the U.S. DOE to advance CCS technology.

The carbon storage project will capture CO2 from ADM's ethanol plant and inject it into a saline reservoir located more than a mile underground. Beginning in early 2011, up to 1 million metric tons of CO2 sourced from the facility will be compressed into a dense, liquid-like state and injected to the Mt. Simon Sandstone formation over a three-year period.

The Mt. Simon Sandstone formation, located at a depth of 6,400 to 7,000 feet, is the thickest and most widespread saline reservoir in the Illinois Basin. The formation has an estimated CO2 storage capacity of approximately 30-110 billion metric tons.

The seismic survey recently completed by MGSC involves the generation of sound waves at the surface level. Sound waves travel through the ground and encounter underlying rock structures, reflecting some of the waves back to the surface. The reflected waves are then processed to generate clean, high-resolution 3D images of the subsurface. This provides a detailed analysis of the structural and stratigraphic configuration of the rocks. According to DOE Regional Carbon Sequestration Partnership Coordinator Traci Rodosta, the process essentially results in a 3-D photograph of the subsurface.

Rodosta said the results of the 3D seismic survey are then compared with fluid and core samples sourced from test wells. "From those tools, we actually tie the rock properties that we see at that well to the seismic survey," she continued. "That gives us a more extensive picture of the subsurface architecture." She noted that rock layers are not formed like a gigantic layer cake, their formation is dependent on the geologic system that has formed them. Essentially, the survey data helps map out the internal structure of the rock formations, as well as indentify any faults in the region.

"It also gives us an idea of faulting, not just at depth, but also shallow," Rodosta said. This allows the researchers to determine any potential migration paths for CO2 that are present in the rock formation. "The primary role of the survey is for us to characterize the subsurface, because until we understand what the subsurface looks like we're not going to have a good understanding of the potential migration of the CO2 plume," Rodosta said. "In turn, by doing this characterization three-dimensionally, what we can also do is determine where we might potentially want to put a monitoring well in the future." According to Rodosta, researchers are especially interested in locating any fault lines that either penetrate, or come close to penetrating, the shale cap rock found around the Mt. Simon formation, which acts as a seal around the saline-containing sandstone structure.

While the Illinois Basin spans 60,000 square miles, this seismic survey studied only 3.82 square miles of the Mt. Simon formation. According to Rodesta, it is possible that similar surveys will be conducted on additional areas in the future specifically for other CCS projects. But, she also noted that any additional 3-D surveys will be project specific. "There is no cookie-cutter approach to this," she said. "Each site will be different based on its geology and the criteria of how much [CO2] is going to be injected into the subsurface."

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