Seismic Velocity and Resistivity Changes during
CO2 Injection into Water-saturated Sandstones

Application of Rock Physics to CO2 Monitoring in Geological Sequestration

Ziqiu Xue
xue@rite.or.jp
Research Institute of Innovative Technology for the EarthInternational Workshop on CO２ Geological Storage , Japan ‘06

Monitoring of Injected CO2• Map the movement of CO2 & the CO2 is being
safely contained within the reservoir.
• Injection of CO2 Causes Wave Velocity toDecrease and the Pore Pressure to Increase .
• Lab Experiments are required to Convert Field
Results of Wave Velocity to CO2 Saturation.

International Workshop on CO２ Geological Storage , Japan ‘06

Laboratory Study and Field Survey
in CO2 Geological Sequestration
Lab-scale

Field-scale•4D Seismic Survey•Crosswell Tomography•Well Logging(sonic, induction, neutron)•Wave Velocity and Resistivity
changes during CO2 injection•Sandstones with different porosityand permeability•Drilled Cores from CO2 injection sites

Geophysical Parametervelocity, resistivity
International Workshop on CO２ Geological Storage , Japan ‘06

Reservoir Parameter
fluid saturation

Wave Velocity Response
due toCO2 Injection in Tako SandstoneInternational Workshop on CO２ Geological Storage , Japan ‘06

P-wave Amplitude (V)

0.10

0.05

post-CO2
pre-CO2Supercritical CO20.00

Vp: -10%-0.05-0.101015202530

Gross Travel Time (microseconds)

P-wave forms obtained from pre- and post- CO2 flooding
in Tako sandstone.
International Workshop on CO２ Geological Storage , Japan ‘06

Experimental setup for P-wave
velocity tomography
Array: 8 x 8#3 for CO2
injection pressure#2 for pore waterpore pressure
Syringe pump #1 for oilhydrostatic pressure
International Workshop on CO２ Geological Storage , Japan ‘06

D=5, L=10cm

Experimental Study of Seismic Wave TomographyTOP87166145134123211101915BTM

H2O/CO2International Workshop on CO２ Geological Storage , Japan ‘06

Sandstone: 23%, 3md

CO2 migration in water-saturated sandstone

CO2Xue and Lei, 2006

Pore space (blue resin)

CO2 flows parallel to bedding plane; Numeric numbers: Elapsed time
International Workshop on CO２ Geological Storage , Japan ‘06

Velocity Reduction vs Pore SpaceS6R6S4R4S3S1R1International Workshop on CO２ Geological Storage , Japan ‘06

Pre-CO2Gas CO2Liq. CO2S.C. CO2Post-CO2-10.7(%)-11.1(%)-16.4(%)(µs)

Ray path: S1-R1
International Workshop on CO２ Geological Storage , Japan ‘06

-5.1(%)
Gas CO2-7.4(%)
liq. CO2-8.5(%)

s.c. CO2101214161820222426283032343638404244(µs)

RayTS-5(S3-R6)
path:.datS3-R6
International Workshop on CO２ Geological Storage , Japan ‘06

Estimation of CO2 Saturation
fromSonic P-wave Velocity

International Workshop on CO２ Geological Storage , Japan ‘06

CO2 saturation?

Velocity reduction: -23%

International Workshop on CO２ Geological Storage , Japan ‘06

Observation Well OB-2

fine-grain sandstone
diameter: 5cm，length: 7cm
1145.49m - 1145.58m
International Workshop on CO２ Geological Storage , Japan ‘06

Experimental System Diagram
Measurements of Vp during injection of
CO2under simulated in-situ P&T conditions.

ical
Supercrit

CO 2P or e W

aterFlow

International Workshop on CO２ Geological Storage , Japan ‘06

2.5

Pore Pressure ： 10 MPa
CO2 Inj.Pres. ： 10.5 MPa
Temperature ： 38℃

Velocity (km/s)

2.0

Breakthough

1.5

1.0

0.5

velocity（%）
0.0020406080

1000

1.0

-20

0.8

-40

0.6-600.4

Pre-CO2: 2.3 km/s
Post-CO2: 1.8 km/s

Amplitude-100- 21.7 %0.2-800International Workshop on CO２ Geological Storage , Japan ‘06

204060Elapsed Time (min)80

0.0100

Amplitude Ratio

Sonic Vp （Zone 2）

Velocity Reduction (%)

Elapsed Time (min)History Matching on Sonic Vp

Estimation of CO2Saturation
with Gassmann theory

Velocity reduction due tobreakthrough of CO2

Xue et al.,2006

Sonic Vp in Observation Well OB-2 at Nagaoka CO2 Injection Site

International Workshop on CO２ Geological Storage , Japan ‘06

13th14th

第13回
0.00
950.000.20

0.80

1.000.00
950.00

0.20

0.40

0.60

16th

第15回

第14回

0.40 0.60

Sc(Uniform)

Depth (m)

15th
0.80

1.00

0.00
950.00

0.20

0.40

0.60

第16回

0.80

1.00

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Sc(Uniform)

Sc(Uniform)

1000.00

1000.00

1000.00

1050.00

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1100.00

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International Workshop on CO２ Geological Storage , Japan ‘06

0.40

0.60

0.80

1.00

Sc(Uniform)

1000.00

CO2 saturation (fraction)

0.20

17th

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第18回

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1.000.00
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950.000.20

第19回
0.40 0.60

Sc(Uniform)

Sc(Uniform)

Depth (m)

19th

20th
第20回

0.80

1.00

0.00
950.001000.00

1000.00

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International Workshop on CO２ Geological Storage , Japan ‘06

0.40

0.60

0.80

1.00

Sc(Uniform)

Sc(Uniform)

CO2 saturation

0.20

21st
0.00
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第21回
0.40 0.60

第23回

第22回

0.80

1.00

0.00
950.000.20

0.400.60

0.80

1.00

Sc(Uniform)

Sc(Uniform)

Depth (m)

23th
0.00
950.001000.00

1000.00

1050.00

1050.00

1050.00

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International Workshop on CO２ Geological Storage , Japan ‘06

0.40

0.60

0.80

1.00

Sc(Uniform)

1000.00

CO2 saturation

0.20

P-wave Veloctiy (km/s)

2.7

1115m

2.5
2.3

P-wave velocity vs CO2 saturation

2.1
1.9
1.7
1.5

0.0

0.2

0.4

0.6

0.8

1.0

2.7

P-wave Velocity (km/s)

CO 2 saturation

1116m

2.5
2.3
2.1
1.91.7
1.5

0.0

0.2

0.4

0.6

0.8

1.0

CO 2 saturation▲： estimated from sonic Vp: predicted with Gassmann theory

P-wave Velocity (km/s)

2.71117m

2.5
2.3
2.1
1.9
1.7
1.5

0.0

0.2

0.4

0.6

CO 2 saturation

International Workshop on CO２ Geological Storage , Japan ‘06

0.8

1.0

Resistivity Changes
caused by
CO2 Injection in Berea SandstoneInternational Workshop on CO２ Geological Storage , Japan ‘06

Resistivity changes during injection of s.c. CO2
into Berea sandstone saturated with artificial formation water

Kubota et al.,2006
International Workshop on CO２ Geological Storage , Japan ‘06

CONCLUSIONS• P-wave velocity and resistivity clearly responded
to CO2 injection into water-saturated sandstones.
Vp: -10% (order);ρ: + 300% (Max)• CO2 migration pattern depends strongly onheterogeneous pore structure and bedding planein porous sandstones.
• Confirmed sonic Vp reduction (-20%) due to CO2
breakthrough with drilled cores retrieved fromthe observation well OB-2.
International Workshop on CO２ Geological Storage , Japan ‘06

Conclusions (cont.)• Successfully applied Gassmann Theory toestimate CO2 saturation from sonic P-wave
velocity.
less Vp decrease: >20% CO2 saturation•Resistivity increases are larger in sandstone
sample (lab-scale) compared to induction
logging (field-scale).
•Supporting developments of cost-effective
methods for CO2 monitoring in geologicalsequestration.
International Workshop on CO Geological Storage , Japan ‘06
２

ACKNOWLEDGMENTS•This project is funded by Ministry of Economy,
Trade and Industry (METI) of Japan.
•We thank staffs of ENAA, Teikoku Oil, OYO Co.,
Geophysical Surveying Co., CRIEP and RITE
involved in Nagaoka pilot CO2 injection project.

International Workshop on CO２ Geological Storage , Japan ‘06