From Bureau of Economic Geology, The
University of Texas at Austin (www.beg.utexas.edu).
Bureau Seminar, November 09, 2007
Pressure evolution and capillary seal
Bureau of Economic Geology
This research investigates the nature of hydrodynamic seal capacity in potential CO2 sequestration reservoirs and the conditions that lead to initial migration from an injection horizon resulting from pressure buildup and vertical brine displacement. An initial assessment suggested that the methodology developed by the natural gas industry could be relevant to CO2 sequestration. Numerical codes adapted from the natural gas storage industry are being modified and extended to investigate the influence that seal thickness and petrophysical properties as well as the rate of pressure buildup have on CO2 migration rates and net volume retained. In methane storage, computed vertical migration rates (and therefore the volume retained) depend on the shape of the injection profile (pressure increase versus time; 'charge rate'), suggesting that optimization of CO2 storage volumes (net capacity) should consider how the CO2 is injected through time in addition to simply the petrophysical properties of the host reservoir and primary seal (threshold capillary entry pressure). Such analyses provide practical guidance regarding the injection profile advisable for a range of seal characteristics. Economic implications of various injection profiles are being evaluated to achieve optimal storage for both seal integrity and economic return.