Risks and Benefits of Geologic Sequestration of Carbon Dioxide - How Do the Pieces Fit?

Hovorka, Susan ^1
1 Bureau of Economic Geology, University of Texas at Austin, Austin, TX.

Geologic sequestration of CO2 as part of the carbon capture and storage (CCS) process has proven potential to provide the needed reduction in atmospheric emissions. Before this process is accepted as a dominant part of the solution, it is important to consider the possibility that hazards resulting from this action will create unacceptable damages. Capture of CO2 from point sources would also create a significant revenue stream as CO2 could be sold for enhanced oil recovery (CO2-EOR). The benefit of CO2 EOR to the economy would be significant, but it is important to examine how CO2 EOR fits into the carbon balance and the long term solution.

Techniques to assure that a sequestration site will retain stored CO2 for geologically significant time periods include site characterization, modeling, and monitoring. Risks from failure of a sequestration site to perform properly include leakage to protected groundwater, impact on ecosystems, return to the atmosphere, and damage to other subsurface resources (gas reservoirs in particular). Assessment shows that maximum damage is limited and moderate, and that risks can be reduced by implementing a permitting process that favors high quality sites with adequate monitoring. CO2 EOR is proposed as a valuable first step to prepare for following even larger volume sequestration in brine bearing permeable units below and isolated from fresh water.

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009