Sensitivity of Pressure MonitoringSensitivity of Pressure Monitoring
for Leak Detectionfor Leak Detection
Sally M. Benson, Rob Sally M. Benson, Rob TrautzTrautz and and ChaoChao Shan Shan
Earth Sciences DivisionEarth Sciences Division
Lawrence Berkeley National Laboratory Lawrence Berkeley National Laboratory
Berkeley, CA 94720Berkeley, CA 94720
[email protected]@lbl.gov
Basic Question Asked?Basic Question Asked?
!! Do pressure transient measurements have the sensitivityDo pressure transient measurements have the sensitivity
needed to detect significant leakage from the storageneeded to detect significant leakage from the storage
formation?formation?
!! What are the most promising and cost effectiveWhat are the most promising and cost effective
deployment approaches?deployment approaches?
Basic Design of the Study (Part I)Basic Design of the Study (Part I)
!! Leakage up a wellLeakage up a well
!! Leakage though aLeakage though alocalized region in thelocalized region in thecaprockcaprock
!! Specified volumetricSpecified volumetricdisplacementdisplacementin the monitoringin the monitoringformationformation
!! Radial flow from a lineRadial flow from a linesourcesource
Monitoring Formation
Caprock
Storage Reservoir
Caprock
Monitoring Well
Drinking Water Aquifer
Not to scale.
CO2
CO2
CO2
CO2
CO2
CO2
Brine Displacement
time
!p
Pressure Buildup
Basic Design of the Study (Part II)Basic Design of the Study (Part II)
!! Leakage up a faultLeakage up a fault
!! SpecifiedSpecifiedvolumetricvolumetricinjection rate ininjection rate inthe storagethe storageformationformation
Monitoring Formation
Caprock
Storage Reservoir
Caprock
Injection Well
Drinking Water Aquifer
Not to scale.
Fault
Brine Displacement
Monitoring Well
CO2
CO2
CO2
CO2
CO2
CO2
time
!p
Pressure Buildup
Detection Limits for Pressure ChangesDetection Limits for Pressure Changes
!! Instrument resolution < 0.0007Instrument resolution < 0.0007
bar (0.01 bar (0.01 psipsi) at formation) at formation
pressurepressure
!! Natural background fluctuationsNatural background fluctuations
–– Atmospheric pressure <~ 0.07 barAtmospheric pressure <~ 0.07 bar
–– Earth tides < ~0.005Earth tides < ~0.005
–– Ocean tides (depends on location)Ocean tides (depends on location)
–– PrecipitationPrecipitation
–– Effects of pumping or other usesEffects of pumping or other uses
!! Instrument drift?Instrument drift?
Assume: Pressure changes greater than 10x instrument resolution can be detected and are diagnostic of leakage ~ 0.007 bar (0.1 psi)
Can be filtered from the data.
Sensitivity Studies (Part I)Sensitivity Studies (Part I)
Detection Sensitivity For Leakage Up a Well Detection Sensitivity For Leakage Up a Well
Q = 0.1%yr,
0.01%yr,
0.001%/yr
0.0001%/yr
x CO2 mass in place
T = kh!g/! = 10-7 to 10-3 m2/s
S = 10-5, 10-4, 10-3
r = 0.1, 0.5, 1, 10 km
CO2 mass in place:
5 Mt, 50 Mt
Monitoring Formation
Caprock
Storage Reservoir
Caprock
Monitoring Well
Drinking Water Aquifer
Not to scale.
CO2
CO2
CO2
CO2
CO2
CO2
Brine Displacement
How long does it take to detect 0.007 barHow long does it take to detect 0.007 bar
(0.1 (0.1 psipsi) pressure buildup?) pressure buildup?
0.0100
0.1000
1.0000
10.0000
1.0E-07 1.0E-06 1.0E-05 1.0E-04 1.0E-03
Transmisivity (m2/s)
Tim
e (
yea
rs)
r = 500 mS = 10-4
Q= 500 tonnes/year(0.01%/year)
r = 500 m, L= 0.01%/yr, CO2=5 Mt0.0001
0.0010
0.0100
0.1000
1.0000
10.0000
1.0E-07 1.0E-06 1.0E-05 1.0E-04 1.0E-03
Transmisivity (m2/s)
Tim
e (y
ears
)
S=10-5
S=10-4
S=10-3
How long does it take to detect 0.007 barHow long does it take to detect 0.007 bar
(0.1 (0.1 psipsi) pressure buildup?) pressure buildup?
Leakage = 0.01%/yr * 5 Mt = 500 tonnes/year
At higher leakage ratesAt higher leakage rates……
r = 500 m, L=0.1%/yr, CO2=5 Mt
0.0001
0.001
0.01
0.1
1
10
1.0E-07 1.0E-06 1.0E-05 1.0E-04 1.0E-03
Transmisivity (m2/s)
Tim
e (
ye
ars
)
S=10-5
S=10-4
S=10-3
Leakage = 0.1%/yr * 5 Mt = 5000 tonnes/year
How close must the monitoring well be toHow close must the monitoring well be to
the leak to detect leakage?the leak to detect leakage?
S=10-4
, L=0.01%/yr, C=5 Mt
0.0001
0.0010
0.0100
0.1000
1.0000
10.0000
100.0000
1.0E-07 1.0E-06 1.0E-05 1.0E-04 1.0E-03
transmisivity (m2/s)
tim
e (
years
)
100 m
1,000 m
500 m
10,000 m
How small a leak can be detected?How small a leak can be detected?
Maybe… it depends on the permeability and thickness of the monitoring horizon.
r = 1,000 m, S=10-4
, C=5 Mt
0.001
0.01
0.1
1
10
100
1.0E-07 1.0E-06 1.0E-05 1.0E-04 1.0E-03
transmisivity (m2/s)
tim
e (
years
)
0.01%/year (500 tonnes/yr)
0.1%/year (5000 tonnes/yr)
0.001%/year50 tonnes/yr)
0.0001%/year(5 tonnes/yr)
Sensitivity Studies (Part II)Sensitivity Studies (Part II)
Detection Sensitivity For Leakage Up a FaultDetection Sensitivity For Leakage Up a Fault
Monitoring Formation
Caprock
Storage Reservoir
Caprock
Injection Well
Drinking Water Aquifer
Not to scale.
Fault
Brine Displacement
Monitoring Well
CO2
CO2
CO2
CO2
CO2
CO2
After Shan, C., I. Javandel, and P. A. Witherspoon, 1995.
x
!
Q = 5 Mt/year injection
TS = 10-6 to 10-3 m2/s
Tm = 2x10-7 to 2x10-4 m2/s
Ss = 10-3
Sm = 2x10-4
Tf = 10-8 m2/sLf = 70 mx = ! = 0.1, 0.5, 1, 5,
10 kmX = 10 m, ! = 2,000 m
CO2 injection rate: 5 Mt/year
How long does it take to detect 0.007 barHow long does it take to detect 0.007 bar
(0.1 (0.1 psipsi) pressure buildup?) pressure buildup?
0.00
0.00
0.01
0.10
1.00
10.00
100.00
1000.00
1.E-06 1.E-05 1.E-04 1.E-03
Transmisivity(m2/s)
Tim
e (
years
)
x = a =100 m x = a = 500 m x = a = 1,000 m
x=a=5,000 m x=10 m, a = 2000 m
1,000
10
1
0.1
0.01
0.001
0.0001
100
Strategy for Optimizing Detection UsingStrategy for Optimizing Detection Using
Pressure Monitoring WellsPressure Monitoring Wells
!! Place monitoring wells nearPlace monitoring wells near
known vulnerabilitiesknown vulnerabilities
–– FaultsFaults
–– Abandoned wellsAbandoned wells
!! Use existing or abandonedUse existing or abandoned
wells for monitoringwells for monitoring
!! Modify injection wells forModify injection wells for
monitoring pressure abovemonitoring pressure above
the injection zonethe injection zone
!! SlimholeSlimhole monitoring monitoring
installationinstallation
xx
xx
xx
x
Injection wells
Abandoned wells
Fault
Dual Purpose Injection and Monitoring WellsDual Purpose Injection and Monitoring Wells
Monitoring Formation
Caprock
Storage Reservoir
Caprock
Injection/Monitoring
Well
Drinking Water Aquifer
Not to scale.
Fault
Brine Displacement
CO2
CO2
CO2
CO2
CO2
CO2
Injection Tubing
Well Casing
Packer
PressureTransducer
CO2
CO2
CO2
CO2
ConclusionsConclusions
!! Under some circumstances pressure measurements could have theUnder some circumstances pressure measurements could have theneeded sensitivity to detect small leakage ratesneeded sensitivity to detect small leakage rates
–– Thin strata with moderate permeability is optimalThin strata with moderate permeability is optimal
–– Site specific assessment neededSite specific assessment needed
!! Leak detection most probable for distance of 1 km or less from theLeak detection most probable for distance of 1 km or less from theleakleak
!! Could be useful for providing early warning of large leaks (< 1 yearCould be useful for providing early warning of large leaks (< 1 yearafter injection begins)after injection begins)
–– Brine displacement also can be detectedBrine displacement also can be detected
!! Optimization needed to employ at reasonable costOptimization needed to employ at reasonable cost
–– Placement of monitoring wellsPlacement of monitoring wells
–– Dual purpose injection and shallow monitoring wellsDual purpose injection and shallow monitoring wells
–– SlimholeSlimhole drilling drilling
!! Unlikely to replace seismic monitoring, but may help to reduce theUnlikely to replace seismic monitoring, but may help to reduce thefrequency or costs of seismic data acquisitionfrequency or costs of seismic data acquisition
!! Particularly useful for assessing known vulnerabilitiesParticularly useful for assessing known vulnerabilities
