Presentation given by Dr Giorgio Caramanna from Heriot-Watt University on "Field study of natural CO2 emissions and laboratory experiments to assess the geochemical impact of potential CO2 seepage on marine environments" in the Storage Technical Session on Monitoring & Verification at the UKCCSRC Biannual Meeting - CCS in the Bigger Picture - held in Cambridge on 2-3 April 2014

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Giorgio Caramanna
and
Mercedes Maroto-Valer
Field study of natural CO2 emissions and laboratory
experiments to assess the geochemical impact of
potential CO2 seepage on marine environments
G.Caramanna@hw.ac.uk
UKCCSRC Network Early Career Researcher Meeting
Cambridge 2-3 April 2014

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•Laboratory simulation of CO2 seepage
•Natural analogues
Deep-water emissions in Japan
Shallow-water emissions in Italy
•Lessons learned
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Outline

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• CO2 can migrate upwards contaminating the seafloor and
the water column
• Mobilization of pollutants, such as heavy metals, following
the changes in pH
• In case of a failure in the injection/transport rig, a high
concentration of CO2 could occur in the closest areas
• High flows of CO2 may destabilize the seafloor (blowout)
• It is therefore important to identify and assess the
consequences of CO2 leakage
Potential effects of seepage

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Laboratory apparatus
• Calcareous sand
crushed limestone
maerl organic sand
• 180 litres of seawater
• 60 litres of CO2 (gas)
2 hours at 0.5 l/m
140 cm
40 cm
60 cm
Pore water
samplers
Multi-gas
injection
It is a simplified and well-
controlled environment to study
the physical and chemical effects
of CO2 on the environment

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Gas bubbling

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y = 8.7657x-0.094
R² = 0.9319
5.50
6.00
6.50
7.00
7.50
8.00
8.50
1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 101 106 111 116
pH
Times (minutes)
pH trend in the water column during injection
pH water column
Power (pH water column)

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R² = 0.9746
5.5
6
6.5
7
7.5
8
8.5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
pH
Days
pH trend in the water column during recovery
pH water column
Linear (pH water column)

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3.10
3.20
3.30
3.40
3.50
3.60
3.70
3.80
3.90
4.00
4.10
4.20
4.30
4.40
4.50
4.60
4.70
4.80
4.90
5.00
5.10
5.20
5.30
5.40
5.50
5.60
5.70
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000
DO
(mg/l)
Elapsed time (seconds)
Dissolved oxygen changes at the water-sediments interface

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Experimental results
• There was a fast response of the system to increased levels
of CO2 with a sharp decrease in pH
• Once the injection stopped, a partial recovery towards the
initial pH values was observed
• Changes in D.O. reflected the increased concentration of
dissolved CO2 in water
• Increasing in alkalinity as result of CaCO3 dissolution
• Boundary effects due to the limited dimensions of the
experimental apparatus are to be considered

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Natural analogues
• CO2 vents are generally associated with volcanic and
geothermal active areas
• The CO2 concentration of the emitted gas is variable and
there is often some % of other gases, typically SO2 and
H2S
• The fluxes range from a few litres to hundreds of litres
per minute

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Why natural analogues are useful
• The boundary conditions are far more realistic than any
possible laboratory simulation
• They can be used to validate results from laboratory
experiments and modelling and to test instruments and
methods for CO2 seepage detection and monitoring

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Kagoshima Bay
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• The Aira caldera and its post-caldera active volcano,
Sakurajima, are the dominant features of Kagoshima Bay
• The caldera is supposed to be more than 22 *103 years old.
The last eruption of Sakurajima was in 1914, and since 1955
there has been a continuous ash emission from the crater
• The maximum depth of the caldera is 200 m
• On the seafloor, some vents emit high temperature fluids
(215oC) and gas composed of CO2, H2S, CH4 and N2
• The vents have been studied by means of manned
submersibles and unmanned vehicles
Kagoshima Bay natural analogue
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AUV and ROV in deep water
In collaboration with Kyushu University
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Panarea Island
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• Submerged caldera with emissions of gas (mainly CO2)
close to the island of Panarea (Italy)
• In 2002, the area was affected by a gas burst with a strong
increase in the CO2 flow likely originated from a degassing
magmatic body
• The flux of the vented CO2 ranges from a few litres to
more than 150 litres/minute with a total flux of up to
70,000 t/year
• Can be studied by scientific divers
Panarea natural analogue
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The main eruption
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Divers in shallow water
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Gas composition
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
%
O2 CO2N2 H2S
3.91 5.68
1.55
89.37

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Gas variation in the water column
O2 +77%
N2 +1,150%
CO2 -85%
Variation in %
2 m above the emission point

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The bubble
exchanges
gas with the
surrounding
environment
CO2
N2, O2
Gas exchange in water

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pH variations
In this map of the pH
values in the area at
10m in depth, the
position of CO2 vents
on the seafloor is
marked by a stronger
reduction in pH values
(purple zone).

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Lessons learned
• Laboratory and field-study can be used to develop reliable
detection and monitoring techniques
•Geochemical techniques are a reliable tool
CO2 is clearly identifiable as gas and from the
pH decrease
The presence of gases other than CO2 should be
addressed for the realistic interpretation of the results
• Good potentiality of natural analogues to be used as
testing facilities

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Further readings

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Acknowledgements
•The Kyushu University and Dr. Kiminori Shitashima
• The University of Plymouth and Dr. Riccardo Rodolfo-
Metalpa for his diving collaboration in Panarea
•The INGV and Dr. Nunzia Voltattorni for the Panarea gas
analysis
•The colleagues who collaborated on the fieldwork and
laboratory activity
•The CICCS – HW University (EPSRC grant EP/F012098/1)
•The UKCCS for supporting my attendance

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Thank you for your kind attention!
Questions?
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