(possible) Value of
airborne conductivity and
magnetics for CCS: test
case at Cranfield
Susan Hovorka
Jeff Paine, Changbing Yang, Mary Hingst
Gulf Coast Carbon Center
Bureau of Economic Geology
Jackson School of Geosciences
The University of Texas at Austin
A Need to Detect and Characterize
over Large Areas
Monitoring point
Surface Leak
Leaking Well
Ideas in assessment by GCCC
using airborne magnetics and conductivity
• Future leakage as result of CO2 escape might
be focused by same paths as other gasses
– Characterize past gas migration (where present)
– Methane is a detectable gas in our study areas
– Methane impacts iron mobilization and
mineralization, detectable magnetic signal
• Document and characterize pre-injection
anomalies in near surface.
• Possible time lapse?
Iron mobilization in the near surface
Typical soil colors
Hematite and limonite
Reduced colors
Mobilization of Fe by methane
P-site
Methane
Mary Hingst
Fe
Depth below ground surface (m)
BG
1-00
1-03
1-05
0
1
2
3
4
5
6
7
8
9
0
200
400
600
800
1000
Concentration (ppm)
1200
1400
1600
Acid-leachable Fe concentrations
Jeff Paine BEG
Jeff Paine BEG
Jeff Paine BEG
Geophysical logging
by J. Paine, BEG
•
•
•
•
Logging 7 water wells for
conductivity and natural gamma
Sand layers at depths from 30 to
100 meters below surface
Sand layers become thicker from
east to west
Clay layers are thick
Regional groundwater flow
• Mainly for domestic uses
•Flows toward southwest
Groundwater levels at
the water wells at the
Cranfield site in 2010
and 2011 range from
130 to 150 ft
E.h. Boswell & G.a. Bednar, 1985
Reactive transport modeling
Flow and Reactive
Transport, assuming all
wells leak, Chloride as
conservative tracer
Observation well
1
0.1
Cl (M)
• Chloride arrival at
nearest observation
well would not occur
until ~70 years after
start of leakage
• Exceedance of SMCL
would take ~100 years
Leak area
0.01
0.001
obs well
leak area
SMCL
0.0001
0
Changbing Yang, BEG and QEA
50
100
Time (yrs)
150
200
Jeff Paine BEG
Jeff Paine BEG
Jeff Paine BEG