Monitoring of CO 2 intrusion in shallow aquifers

Transcription

1 Monitoring of CO 2 intrusion in shallow aquifers D. Schäfer S. Fahrner, R. Köber, A. Peter, C.E. Wiegers, A. Dahmke Institute of Geosciences Christian-Albrechts-Universtität zu Kiel Anlass, Datum IEAGHG Potsdam June 2011

2 Monitoring of shallow aquifers why? Public acceptance Strange things happening at the Weyburn EOR site Imagine you have not performed any monitoring of shallow aquifers Photos: Site history, SW W2M near Weyburn, Saskatchewan, Cameron and Jane Kerr, ecojustice

3 Monitoring of shallow aquifers why? EU directive 2009/31/EC, Article 13 carry out monitoring for the purpose of detecting significant adverse effects for the surrounding environment, including in particular on drinking water 3

4 Monitoring of shallow aquifers what? where? Monitoring aim and location Detect CO 2 (and saline water) intrusion in the deepest freshwater aquifer? Will this be possible? Idealised geological structure northern Germany freshwater partially saline saline 4

5 CO 2 gas phase distribution over time confined aquifer saturation CO 2 gas phase dissolved CO 2 50 days 182 days 365 days [-] [kg CO2 /kg w ] Leakage rate: l min-1 m-2 Wiegers et al., unpublished 5

6 Geochemical reactions - setup Small pool below aquitard 0.17 cm/d Aquifer depth 300m T = 19 C P = 31 bar initially equilibrium with: - Calcite - Kaolinite - SiO 2 (a) - K-feldspar Simulation of instantaneous equilibrium for: - Calcite - Kaolinite - SiO 2 (a) Kinetic dissolution of: - K-feldspar Ion exchange included 6

7 Geochemical reactions calcite dissolution only Z Z Time: 231 days X Y 0 X Y mol/kg w C ph Z Z X Y 0 X Y mol/kg w mol/kg w 40 Calcite 40 Ca initial concentration 0.64 gcaco 3 / kg sediment

8 Release of heavy metals, e.g. Pb precipitation release Complex model with 9 minerals and surface complexation required Main release due to surface complexation In sulfidic aquifers precipitation possible In aerobic aquifers no precipitation expected Fahrner et al., submitted 8

9 Monitoring parameters Changes depend on the (in detail unknown) sediment mineral composition Choose parameters which do not depend on the sediment composition Choose parameters measurable by permanent sensors TIC will always increase (better measurable: dissolved CO 2 ) Electrical conductivity increases mainly in calcite containing systems ph will decrease, but mainly in calcite free systems Parameter combination sensitive in aquifers with or without calcite Allows detection of saline water intrusion 9

10 CO2 injection test 100m 200m Foto Former russian military air base 100 km north of Berlin Test site 100m x 200m Quaternary sand aquifer 72 Groundwater sampling points Injection test was performed from (10 days) Monitoring from 05/10 09/11 10

11 Schematic test site design 3 injections wells, 18m below surface Injection rate of 10 L/min at each well 10 days of injection (840 kg CO 2 in total) ~ 6 months groundwater monitoring Further site investigations before, during and after the injection test: -Geophysical investigations 18m -Soil, soil gas and groundwater analyses -Microbial investigations and analyses -Isotope analyses Peter et al., unpublished 11

12 Preliminary results, 3 weeks after end of injection TIC [mg/l] SF [µg/l] GWM4F ML8E-3 ML6F-3 ZZ Z1 ZZ ZZ ML2E-3 ML1G GWM2D ML1G ML2C Inj2 450 GWM1F ML1E GWM1D ML1C Inj1 ML1B ML3E-3 Z GWM3D GWM1A ML3C GWM5F Inj GWM5F Z Z ZZ6-3 0 ZZ ZZ4 ZZ4 GWM1F GWM4F ML8E-3 ML6F-3 ZZ7-3 ZZ2-3 Z4 ML2E-3 ML1E-3 ML3E-3 Z1 GWM2D ML2C-3 Inj2 GWM1D ML1C-3 Inj1 ML1B-3 GWM3D ML3C-3 Inj3 Z3 ZZ6-3 ZZ5-3 ZZ3-3 Z ZZ4 GWM1A ZZ ph ML1G-3 GWM4F ML8E-3 ML6F-3 ZZ7-3 Z1 ZZ2-3 ZZ5-3 ML2E-3 GWM2D ML2C-3 GWM1F Inj2 ML1E-3 GWM1D ML1C-3 Inj1 ML1B-3 ML3E-3 GWM3D ML3C-3 GWM5F Inj3 Z4 Z3 ZZ6-3 ZZ3-3 Z GWM1A Si [mg/l] ML1G-3 GWM5F ZZ3-3 GWM4F ML8E-3 ML6F-3 ZZ7-3 Z1 ZZ2-3 ZZ5-3 GWM1F ML2E-3 approx. flow direction ML1E-3 ML3E-3 GWM2D ML2C-3 Inj2 GWM1D ML1C-3 Inj1 ML1B-3 GWM3D ML3C-3 Inj3 Z4 Z3 ZZ6-3 injection Z2 GWM1A Peter et al., unpublished 12

13 Compilation of monitoring methods Method evaluation containing over 60 methods, method descriptions, sensitivities, literature references, costs, development status, method profiles Köber et al., unpublished 13

14 Contribution of monitoring methods to EU directive Köber et al., unpublished 14

15 Potential size of the monitoring area monitoring area 211 km 2 r=5,7 km 2,5 km X direction [m] phase body 100 km 2 2,5 km Leaking CO 2 will not migrate straight upwards Potential leakage paths depend on the site Phase body of about 500 Mt CO 2 Estimated by Chadwick et al. (2009) Geometry depends on the storage formation 15

16 Scale impression magnification ~ 400m Possible plume size reservoir Underlying map: Ibiza only to get an impression of the scales CO 2 leakage pressure / salt water intrusion 16

17 Required number of observation wells Plume size (after ~ 1year): 400m * 100m = m 2 Detektierbarkeit geochemischer Veränderungen Monitoring area: 200 km 2 = m 2 Number of observation wells, if only 1 well shall be positioned within the plume: This estimation is also valid for other point-measurements Detection via point measurements might not comply with the principle of proportionality 17

18 Monitoring concept Split the site monitoring into two parts: a) Initial detection (annually?) repeated monitoring for a long time monitoring of a large area (some m 2 ) only detection of a possible leakage required, no quantification b) Detailed investigation only performed in the unlikely case of leakage or at known potential leakage pathways small scale investigation (some m 2 ) detailed quantification of all adverse effects on groundwater quality quantification of leaking CO 2 mass 18

19 Monitoring methods a) Initial detection plant stress, decrease of chlorophyll, detectable by plane or satellite (ZERT) airborne geophysical methods (electromagnetic) (CLEAN / MOPA-2?) pressure increase in shallow confined aquifers due to intrusion of CO 2 or saline water b) Detailed investigation observation wells & analysis of water samples permanent sensors geoelectrical measurements. and a lot more see NETL best practice manual, ZERT, CLEAN project 19

20 Airborne electromagnetic measurements Geological information down to 300m Mean resistivity: 110 to 120 m depth 20

21 Conclusions Applicable monitoring concept available: Detection of unknown CO 2 sources - Currently only few comprehensive detection methods exist - Promising approaches: geoelectrical measurements, pressure, plant stress (?) Monitoring of known CO 2 sources or potential leakage paths - Near surface investigation methods are available and have been tested - Numerical models are required for data interpretation, input parameters and numerical stability are issues 21

22 Conclusions To do: - Check the applicability of methods at depth down to ~ m - Check the accuracy of detailed monitoring methods for quantification of CO 2 - Test new methods, their applicability and reliability in numerical models - If they work in the model, test them in reality (=> real sites required) - Baseline monitoring of natural fluctuations (=> real sites required) - Combine the detection and monitoring with intervention methods 22

23 Funding: Joint project CO 2 -MoPa Part of the F&E framework Joint project CLEAN Part of the F&E framework Joint project CO 2 injection test 23