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  1. UKCCSC Meeting18th AprilNottinghamNatural analogues of CO2 leakage from the Colorado PlateauStuart Gilfillan, Stuart Haszeldine, Zoe Shipton and Mark Wilkinson

  2. Key Questions • How do natural CO2 storage sites fail? - Faults, lithology, caprock seal and groundwater regime. • What are the pathways of CO2 migration to the surface? - Can we predict/prevent leakage in engineered sites? • How long does CO2 migration to the surface take? - CO2 needs to be stored for 10,000 years. • Can leakage of CO2 be monitored and quantified? - Which chemical tracers can be used. - How effective are they at monitoring natural CO2 leakage?

  3. Colorado Plateau

  4. Colorado Plateau Green River Seeps and Salt Wash fault zone, Utah

  5. Colorado Plateau Green River Seeps and Salt Wash fault zone, Utah • Cold water springs and geysers driven by pressure of CO2. - Gas is 95 - 99% CO2- 0.5 - 3.5 % N2- Trace noble gases. • CO2 release from > 80ka. • Where does this water and CO2 originate from? • How is this CO2 being transported to the surface? Crystal geyser, Utah

  6. Origin of the Water? • Salinity of erupted water indicates migration of water from deep aquifer.

  7. Origin of the Water? Deep aquifer Shallow aquifer

  8. Origin of the CO2? From Ballentine et al. 2002 3He Magmatic Component

  9. Origin of the CO2? From Ballentine et al. 2002 Atmospheric Component 20Ne 36Ar 84Kr AquiferRecharge 3He Magmatic Component Formation Water

  10. Atmospheric Component 20Ne 36Ar 84Kr AquiferRecharge 3He Magmatic Component Formation Water Origin of the CO2? From Ballentine et al. 2002 Accumulate in groundwater 4He 21Ne 40Ar In-situ production Radiogenic Component

  11. Origin of the CO2 – CO2/3He ratio • Mantle CO2/3He range: 1 x 109 – 1 x 1010 • Measured from Mid Ocean Ridge Basalts - MORBs

  12. Origin of the CO2 – CO2/3He ratio 1.00e+12 1.00e+11 1.00e+10 1.00e+9 1.00e+8 1.00e+7 1.00e+6 70 75 80 85 90 95 100 CO Concentration (%) 2 Above 1 x 1010: Crustal CO2 Mantle (MORB) range: 1 x 109 – 1 x 1010 CO2/3He Ratio Below 1 x 109: CO2 lost relative to 3He.

  13. Origin of the CO2 – CO2/3He ratio 1.00e+12 Green River Seeps 1 - 16% Mantle CO2 1.00e+11 1.00e+10 Mantle (MORB) range: 1 x 109 – 1 x 1010 Mantle (MORB) range: 1 x 109 – 1 x 1010 CO2/3He Ratio 1.00e+9 1.00e+8 1.00e+7 1.00e+6 70 75 80 85 90 95 100 CO Concentration (%) 2 • Predominantly crustal derived CO2 erupted from the Green River seeps. • Small mantle component → 1 – 16%

  14. Conclusions

  15. Other natural analogues of CO2 leakage Hurricane Fault, Utah • Active, steeply dipping normal fault ~ 250 km long, ~2.5 km displacement. • CO2 & 40°C water discharges from fault zone. • Noble gas and δ13C (CO2) analysis underway. • No evidence of a CO2 reservoir at depth. Hurricane fault looking north www.skytrailsranch.com

  16. Other natural analogues of CO2 leakage Hurricane Fault, Utah • Active, steeply dipping normal fault ~ 250 km long, ~2.5 km displacement. • CO2 & 40°C water discharges from fault zone. • Noble gas and δ13C (CO2) analysis underway. • No evidence of a CO2 reservoir at depth. St. Johns Dome • Large natural CO2 reservoir (445 billion m3). • CO2 rich surface seeps and travertines. • Composition of deep gas and waters known. • Can natural CO2 can be chemically tagged? e.g. using δ13C(CO2) and/or noble gases.

  17. St. Johns Dome Workflow • Water samples collected from 18 surface seeps - 14C & tritium for groundwater dating. - Solute chemistry. - Noble gas, δ13C(CO2), δ18O and δD isotopes. • Compare composition of surface seeps to known chemistry of reservoir fluids. • Use geochemical modeling to determine and quantify mineralogy changes as CO2 migrates. • Reservoir models underway to investigate CO2 migration pathways and timescales.

  18. Summary • How do natural CO2 storage sites fail? - Primary mechanism is migration along fault planes. • What are the pathways of CO2 migration to the surface? - CO2 is dissolved into the groundwater and transported along faults. • How long does CO2 migration to the surface take? - Unknown at present, dating of CO2 deposits will hopefully provide a timeframe. • Can leakage of CO2 be monitored and quantified? - Yes, a baseline geochemical survey helps a lot!