According to Google Scholar, “Degradation of Well Cement by CO2 under Geologic Sequestration Conditions,” a research paper jointly authored by the U.S. Department of Energy, Carnegie Mellon University, and RJ Lee Group, has now been cited more than 200 times in scientific journals. This first paper in a series of three, focuses on how the curing conditions influence Portland cement attack by carbonic acid in a geologic sequestration setting. Prior to these studies, there was significant concern that the chemical incompatibility between CO2 and wellbore cement would compromise CO2 storage in the deep subsurface. All three studies were published in the journal Environmental Science & Technology (2007, 2008, and 2009) as a collaborative effort. Principal investigator for this research was Dr. Brian Strazisar (formerly with the U.S. Department of Energy, now a cement and concrete expert with RJ Lee Group). Another co-author, Niels Thaulow, is a long-time consulting expert with RJ Lee Group.The optical (left) and electron (right) micrographs show the extent of alteration of wellbore cement by CO2 saturated water. Between the degraded outer edge of the sample and the unaltered interior is a dense carbonated region that slows diffusion of reactive fluids.[/caption]
Of major significance is that the studies confirm that damage to cement due to diffusion and reaction with CO2 is very limited in the subsurface with most experiments showing cement degradation to be less than a millimeter’s depth after a year. When research samples were compared to field samples that had been exposed for decades, results verified that the cement that was historically used in deep wellbores can be highly effective in preventing CO2 migration.
- The first benchmark paper, “Degradation of Well Cement by CO2 under Geologic Sequestration Conditions,” describes the laboratory experiments used to reveal the fundamental diffusion/reaction process by which CO2 can alter wellbore cement in the deep subsurface.
- The second paper, “Rate of CO2 Attack on Hydrated Class H Well Cement under Geologic Sequestration Conditions,” (cited 100 times), demonstrates that the reaction slows significantly in the long term due to precipitation of a carbonate barrier within the pore space of the cement.
- The third paper, “CO2 Reaction with Hydrated Class H Well Cement under Geologic Sequestration Conditions: Effects of Flyash Admixtures,” reveals how common cement additives can affect the process.
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