From Bureau of Economic Geology, The
University of Texas at Austin (www.beg.utexas.edu).
Bureau Seminar, September 8, 2006
Is there really enough space to “put it back”? Capacity estimation for geologic storage of CO2
Policy makers want to know how much carbon capture and storage (CCS) can be relied upon to contribute to reduction in atmospheric release of CO2. One commonly requested information item is the capacity of geologic media to store CO2 on an international, US, regional, and local scale. Is the space in the subsurface adequate to store the volumes that would be produced if capture and storage was to be widely implemented? After giving some background on the volumes involved, we suggest that to estimate and communicate storage capacity it is essential to define the boundary conditions of the volume to be filled and the risk cut-off that determines the time/rate/volume at which injection must be stopped. Looking at large volumes of CO2 storage in pore space previously filled only with brine, we examine four combinations of boundary condition and risk avoided: (1) structural or stratigraphic trap: CO2 spills out of trap, (2) open trap/volume: CO2 escapes from volume, (3) hydrologically closed basin: mechanical or capillary entry pressure of seal is exceeded, and (4) hydrologically open basin: unacceptable displacement of brine.