Dating CO2 leakage rates from a natural analogue for CO2 storageZoe Shipton (GU), Neil Burnside (GU/SUERC), Rob Ellam (SUERC), Ben Dockrill (Chevron)

CO2 Capture Project Statoil, Norsk Hydro, Shell, BP, Eni, EnCanaSuncor, ChevronTexaco, Norway, EU, US DOE

Geological setting

Shipton et al. 2005

Present LeakageOil seep

Past Leakage

Dockrill 2006, Dockrill and Shipton 2008

LGWF

MF

SWFs

Dockrill and Shipton 2008, Vrolijk et al. 2006

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

Leak points spread along the faults as pathways become completely sealed

Flow not continuous - periods of inactivity indicate intermittent flow regime to the surface

Volumetric estimates

min. LGW travertine volume 1.5 x 105 m3 = 4.3 x 108 kg CO2

if 10% of CO2 trapped in travertine ~ 1.9 x 109

kg CO2 leaked over ~80-110 k yrs

Time- averaged flux > 0.84 kg/m2/yr = 0.6μmol/m2/s forest floor 2 to 20μmol/m2/s (Drewitt et al., 2002) Mammoth Mtn tree kill avg 400μmol/m2/s (Benson & Hepple

05)

Gouveia et al. (2005) Crystal Geyser emits CO2 ~ 12 ktonnes/yearRecent increase due to drilling?Constraints on volume through time from new dates

combined CO2 storage capacity of fault-sealed traps ~ 0.6 - 6.3 MtDependent on saturation state and density of CO2Assuming leakage confined to above trap

leak rate of over ~ 0.2% to 1.9% every 500 yrs

Natural CO2 reservoirs in Utah

= laboratory to study leakage of CO2

natural springs boreholeselevated 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?