1. Dating CO 2 leakage rates from a natural analogue for CO 2 storage Zoe Shipton (GU), Neil Burnside (GU/SUERC), Rob Ellam (SUERC), Ben Dockrill (Chevron) CO 2 Capture Project Statoil, Norsk Hydro, Shell, BP, Eni, EnCana Suncor, ChevronTexaco, Norway, EU, US DOE

2. Geological setting Shipton et al. 2005

3. Present Leakage Oil seep

4. Past Leakage Dockrill 2006, Dockrill and Shipton 2008

5. LGWF MF SWFs Dockrill and Shipton 2008, Vrolijk et al. 2006

6. Individual mounds active for up to ~10ka Evidence of reactivation of these pathways with 3 distinct mounds ranging in age of ~45ka Flow pathways switch repeatedly through time

7. Leak points spread along the faults as pathways become completely sealed Flow not continuous - periods of inactivity indicate intermittent flow regime to the surface

8. Volumetric estimates min. LGW travertine volume 1.5 x 10 5 m 3 = 4.3 x 10 8 kg CO 2 if 10% of CO 2 trapped in travertine ~ 1.9 x 10 9 kg CO 2 leaked over ~80-110 k yrs Time- averaged flux > 0.84 kg/m 2 /yr = 0.6μmol/m 2 /s forest floor 2 to 20μmol/m 2 /s (Drewitt et al., 2002) Mammoth Mtn tree kill avg 400μmol/m 2 /s (Benson & Hepple 05) Gouveia et al. (2005) Crystal Geyser emits CO 2 ~ 12 ktonnes/year Recent increase due to drilling? Constraints on volume through time from new dates combined CO 2 storage capacity of fault-sealed traps ~ 0.6 - 6.3 Mt Dependent on saturation state and density of CO2 Assuming leakage confined to above trap leak rate of over ~ 0.2% to 1.9% every 500 yrs

9. Natural CO 2 reservoirs in Utah = laboratory to study leakage of CO 2 natural springs boreholes elevated soil gas? Observed changes in flow pattern may be caused by: sealing of fault pathways by carbonate precipitation changes in stress on faults or regional hydrology ~ 30 to 300% of total trap capacity leaked over 110 kyrs What leak rate acceptable for industrial storage?