Hydrogeochemical Characterization of Leaking, Carbon Dioxide—Charged Fault Zones in East-Central Utah, With Implications for Geological Carbon Storage
Contribution to Book
Carbon Sequestration and Its Role in the Global Carbon Cycle
Brian J. McPherson & Eric T. Sundquist
American Geophysical Union
We examined a natural, CO2-charged subsurface system located near two fault zones in East-Central Utah that is analogous to engineered sequestration sites. Geologic information and geochemical and isotopic data from water and gas samples were used to develop a conceptual model of the flow system. This flow-system description indicates that CO2 from a depth >800 m migrates upward through a system of shallower, stacked aquifers. The geologic structure in the area serves to focus the CO2-rich waters at the location of a faulted, anticlinal trap. The faults in the area impede horizontal flow but allow vertical leakage through thick, low-permeability formations. An important implication from this CO2-sequestration analog is that leakages occur along discrete flow paths in the subsurface; thus, in sequestration scenarios, detailed understanding of discrete flow paths will be necessary. Another implication is that groundwater can transport a significant amount of CO2, and thus, sampling groundwater chemistries from wells may be a better way to identify leakages than using monitoring techniques at the surface. Finally, even though mineralization occurs during CO2 leakage to the surface, self-sealing has not occurred at this natural analog and may not occur at engineered sequestration sites.
Heath, J. E., Lachmar, T. E., Kolesar, P. T., and Evans, J. P., Hydrogeochemical Characterization of Leaking, Carbon Dioxide—Charged Fault Zones in East-Central Utah, With Implications for Geological Carbon Storage, in: McPherson, B. J., Sundquist, E., eds., Carbon Sequestration and Its Role in the Global Carbon Cycle AGU Geophysical Monograph Series 183, p. 147- 158.