Capturing carbon: Studies test safety of sequestration
Burning oil and coal, which are rich in carbon, releases the greenhouse gas carbon dioxide. Until alternative fuels become mainstream, one viable option to cut carbon emissions is to capture the gas and inject it into sediments deep underground, according to Princeton’s Michael Celia *79, chair of civil and environmental engineering.
However, the technology will only succeed if the gas stays safely stored for hundreds, even thousands of years. Celia and colleagues in his department are trying to make sure that it does.
Old oil and gas fields would be convenient sites to inject and store captured carbon dioxide, but the old wells also create potential routes for the gas to escape. “A typical injected CO2 plume may encounter tens to hundreds of these existing wells,” Celia said. Working with the Alberta (Canada) Geological Survey, Celia is developing large-scale 3D models to simulate how the gas might move, interact with the wells and potentially leak.
Professor Jean Prevost is also simulating the behavior of injected CO2, predicting how carbonic acid formed by the CO2 will degrade the cement used to plug old wells. Professor George Scherer is conducting laboratory experiments to answer the same question, while associate professor Catherine Peters is studying the structure and mineral composition of rock samples from Alberta to understand how they react with carbonic acid.
So far, their conclusions are mixed: in many cases the acid cannot eat through rock or cement to reach the surface, but in situations where the cement already has defects, the acid can enhance the damage and lead to CO2 leakage. These results could influence the development of regulations and permitting criteria for large-scale injection operations, Celia said.