1. School of GeoSciences Subsurface Research Group UKCCSC Meeting 18 th April Nottingham Natural analogues of CO 2 leakage from the Colorado Plateau Stuart Gilfillan, Stuart Haszeldine, Zoe Shipton and Mark Wilkinson

2. School of GeoSciences Subsurface Research Group Key Questions 1.How do natural CO 2 storage sites fail? - Faults, lithology, caprock seal and groundwater regime. 2.What are the pathways of CO 2 migration to the surface? - Can we predict/prevent leakage in engineered sites? 3.How long does CO 2 migration to the surface take? - CO 2 needs to be stored for 10,000 years. 4.Can leakage of CO 2 be monitored and quantified? - Which chemical tracers can be used. - How effective are they at monitoring natural CO 2 leakage?

3. School of GeoSciences Subsurface Research Group Colorado Plateau

4. School of GeoSciences Subsurface Research Group Colorado Plateau Green River Seeps and Salt Wash fault zone, Utah

5. School of GeoSciences Subsurface Research Group -Cold water springs and geysers driven by pressure of CO 2. - Gas is 95 - 99% CO 2 - 0.5 - 3.5 % N 2 - Trace noble gases. -CO 2 release from > 80ka. -Where does this water and CO 2 originate from? -How is this CO 2 being transported to the surface? Green River Seeps and Salt Wash fault zone, Utah Crystal geyser, Utah Colorado Plateau

6. School of GeoSciences Subsurface Research Group Origin of the Water? -Salinity of erupted water indicates migration of water from deep aquifer.

7. School of GeoSciences Subsurface Research Group Deep aquifer Shallow aquifer Origin of the Water?

8. School of GeoSciences Subsurface Research Group From Ballentine et al. 2002 Magmatic Component 3 He Origin of the CO 2 ?

9. School of GeoSciences Subsurface Research Group From Ballentine et al. 2002 Magmatic Component 3 He Atmospheric Component Aquifer Recharge 20 Ne 36 Ar 84 Kr Formation Water Origin of the CO 2 ?

10. School of GeoSciences Subsurface Research Group From Ballentine et al. 2002 Magmatic Component 3 He RadiogenicComponent In-situproduction 4 He 21 Ne 40 Ar Atmospheric Component Aquifer Recharge 20 Ne 36 Ar 84 Kr Formation Water Accumulate in groundwater Origin of the CO 2 ?

11. School of GeoSciences Subsurface Research Group Origin of the CO 2 – CO 2 / 3 He ratio Mantle CO 2 / 3 He range: 1 x 10 9 – 1 x 10 10 Measured from Mid Ocean Ridge Basalts - MORBs

12. School of GeoSciences Subsurface Research Group 707580859095100 1.00e+6 1.00e+7 1.00e+8 1.00e+9 1.00e+10 1.00e+11 1.00e+12 CO 2 Concentration (%) Mantle (MORB) range: 1 x 10 9 – 1 x 10 10 Above 1 x 10 10 : Crustal CO 2 Below 1 x 10 9 : CO 2 lost relative to 3 He. Origin of the CO 2 – CO 2 / 3 He ratio CO 2 / 3 He Ratio

13. School of GeoSciences Subsurface Research Group Predominantly crustal derived CO 2 erupted from the Green River seeps. Small mantle component 1 – 16% Mantle (MORB) range: 1 x 10 9 – 1 x 10 10 1 - 16% Mantle CO 2 Origin of the CO 2 – CO 2 / 3 He ratio 707580859095100 1.00e+6 1.00e+7 1.00e+8 1.00e+9 1.00e+10 1.00e+11 1.00e+12 Green River Seeps CO 2 Concentration (%) CO 2 / 3 He Ratio Mantle (MORB) range: 1 x 10 9 – 1 x 10 10

14. School of GeoSciences Subsurface Research Group Conclusions

15. School of GeoSciences Subsurface Research Group Other natural analogues of CO 2 leakage Hurricane Fault, Utah -Active, steeply dipping normal fault ~ 250 km long, ~2.5 km displacement. -CO 2 & 40°C water discharges from fault zone. -Noble gas and δ 13 C (CO 2 ) analysis underway. -No evidence of a CO 2 reservoir at depth. Hurricane fault looking north www.skytrailsranch.com

16. School of GeoSciences Subsurface Research Group Other natural analogues of CO 2 leakage Hurricane Fault, Utah -Active, steeply dipping normal fault ~ 250 km long, ~2.5 km displacement. -CO 2 & 40°C water discharges from fault zone. -Noble gas and δ 13 C (CO 2 ) analysis underway. -No evidence of a CO 2 reservoir at depth. St. Johns Dome -Large natural CO 2 reservoir (445 billion m 3 ). -CO 2 rich surface seeps and travertines. -Composition of deep gas and waters known. -Can natural CO 2 can be chemically tagged? e.g. using δ 13 C(CO 2 ) and/or noble gases.

17. School of GeoSciences Subsurface Research Group St. Johns Dome Workflow -Water samples collected from 18 surface seeps - 14 C & tritium for groundwater dating. - Solute chemistry. - Noble gas, δ 13 C(CO 2 ), δ 18 O and δD isotopes. -Compare composition of surface seeps to known chemistry of reservoir fluids. -Use geochemical modeling to determine and quantify mineralogy changes as CO 2 migrates. -Reservoir models underway to investigate CO 2 migration pathways and timescales.

18. School of GeoSciences Subsurface Research Group Summary 1.How do natural CO 2 storage sites fail? - Primary mechanism is migration along fault planes. 2.What are the pathways of CO 2 migration to the surface? - CO 2 is dissolved into the groundwater and transported along faults. 3.How long does CO 2 migration to the surface take? - Unknown at present, dating of CO 2 deposits will hopefully provide a timeframe. 4.Can leakage of CO 2 be monitored and quantified? - Yes, a baseline geochemical survey helps a lot!