1CCS Technical Workshop 2010

CO2挙動モニタリング技術

海域におけるCO2挙動観測・解析技術の挑戦

OBC（常設Ocean Bottom Cable方式）
Toward Offshore CCS Seismic Monitoring－Development of Permanent OBC System－

株式会社地球科学総合研究所
研究開発部 高橋 明久
Akihisa (May-Q) Takahashi, Dr. Eng.
JGI, Inc
2010.12.9

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JGI, Inc., Who?
A subsidiary ofJapan Petroleum Exploration Co., Ltd. (JAPEX)
Leading Japanese oil and natural gas E&P technologies

Group Companies
JGI, Inc.(JGI)
G & G, Monitoring
SK Engineering Co., Ltd. (SKE)
Drilling
Geophysical Surveying Co., Ltd. (GSC)
Wireline Techs
With extent expertise and knowledge of E&P in Oil/Gas
fields, JAPEX group will go ahead the development oftechnologies for CO2 Geological Sequestration, throughG&G evaluation, drilling, well logging, reservoir
engineering, monitoring and comprehensive coordination.

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Necessity of Permanent OBC
for CCS in Japan• More strict requirements for the CCS monitoring
exist in Japan as the candidate aquifers for theCO2 injection are mainly located near highly
populated areas along the coast.
• High-fidelity time-lapse 3D seismic survey isnecessary for the monitoring of CO2 geologicalsequestration.
• Passive micro-seismic observation is mandatorywhen following the guideline from METI.

4Advantages of Permanent OBC• Removal of uncertainty of the sensor
positions• Consistent receiver response for thedifferent surveys• Prompt and economical operations of thetime-lapse surveys• Passive observation of micro-earthquakes

Concept of Permanent OBC System
3km

3km

OBC lines (every 300m ）Shoreline

Location of injection well
Land Station

5Concept ofPermanent OBC
System

5km
3km

65km

3km

OBC lines (every 300m ）Shoreline

Airgun lines (every 200m)
Location of injection well
Land Station3D Seismic Survey (Shallow Marine)
by Japan CCS Co., Ltd.

OBC cable deployment (by JGI）

From JCCS WebsiteSensor at the sea bottom

3D seismic surveys using temporal deployment of OBC
have already been done in Japan.

7

Data Acquisition
using the permanent OBC system
in Tomakomai, JAPANby RITE

8

9OBC ExperimentIndex Map
Ｌａｎｄ Ｓｔａｔｉｏｎ for OBS
Land Station
For Wave Height
Observation

OBC cable 1.6km
Wave Height
Observation
Cable(buried)

300m both side of wave heightobservation system is out thefishing area.

10Permanent OBC Experiment ConfigurationMarker Buoy with Anchor

Land Station

Sea Surface〜10mdAnchor

Un-armouredcabled
Armoured Extension Cable
d0.4kmArmoured Cable with Sensor Unit
1.2km(50m×8units×3cables）
d

Acoustic Transponders were set
at each sensor unit

Buried from
Ebb Tide Line to
Utility Pole

11OBC Deployment
Configuration

50m x 8 module / cableMax. Pressure

34.5 MPa【Cable】【Module】

Diameter

22.6 mm

Weight (Air)1.77 kg/m

Weight (Water)

1.46 kg/m

Diameter

86 mm

Length1.37 mWeight (Air)12.6 kg

Weight (Water)

7.7 kg12Burial from
Ebb Tide Line to
Utility PoleOBC Setting （Landward Ch1, Ch.3)
After Deployment
Ch1

Ch 3

Before Retrieval
Ch 1

Ch 3

Hard to bury sensors when deploying due to cable tension.
Most landward sensors buried when retrieving.

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OBC Setting （Seaward Ch21, Ch.24)
After Deployment
Ch 21

Ch 24

Before Retrieval
Ch 21

Ch 24

Situation not much changed.

14

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Rotation of Sensor Units
Bad Weather due to depression
Landward Ch.1-8（Max. 6ﾟ rotation）

Airgun Shooting A
7/24

Airgun Shooting B
8/31

Seaward Ch.17-24（Max. 24ﾟ rotation）
7/23

2 Months

9/23

16Overview of Airgun shooting
Land Station

Airgun (480in3）

Shooting Vessel（43ton）

Aungirit ngoohSmk2
3.

OBCcm（k.61lesbaaveitcm）
k1 .2

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Schedule of Airgun Shooting A (7/24)
Tide Level

Airgun Volume
480 in3→300 in3
7/24 Tomakomai

Sea level (cm)160

Tomakomai

80

0Shootings on the same line
were repeated with thedifferent tide levels(A1-A7)A3
A4
A5A6A7A1
A20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2021 22 23(hour)Line Name LegendA1H: Shooting A(7/24) 1st run Hydrophone
B6G: Shooting B(8/31) 6th run Geophone

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Common Shot GatherX(Inline)

Y1

Y2Hydrophone

Reflections

Courtesy of RITE

Common Receiver Gather (Ch1.）
Geophone（After Rotation）
X(Inline)

Y（Crossline）

Z（Vertical）

Vnmo=1650 m/s

Vnmo= 975 m/s

P wave reflections

Possible P-SV convertedwaves. Further study isnecessary.
Courtesy of RITE

Recorded on 8/31

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OBC Retrieval

Barnacles

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Results from Data Analysis• Noise Condition• Repeatability （Shot/Receiver Loc. Uncertainty）• Tidal Change• Airgun Volume Change• Possible Use of P-SV Converted Waves• Index for ４D Detectability• Observation of Micro-Seismic

22Geophone Noise RecordGood WeatherLand（秒）
0

7/23 00：00

InlineCrossline

Sea LandVerticalInline

Bad Weather

Sea

7/30 00：00

Crossline

Vertical
05

5

10

10

15

Courtesy of RITE

15

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Noise Analysis
Vertical Axis: RMS Amplitude
Land

Good Weather Sea Land Bad Weather

Sea

Geophone(Inline)Geophone(Crossline)

Geophone(Vertical)
Loc.1

Loc.24 Loc.1

Loc.24

Loc.1

Loc.24 Loc.1

Loc.24

HydrophoneGeophones (Inline) are stable. Geophones (crossline) noise level differenceis larger seaward. Hydrophone noise is larger landward.
Courtesy of RITE

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Stack Section from A1Hydrophone

Two Way Travel Time in sec

LandHydrophone(flexbin)

Geophone
VerticalGeophone(flexbin)

Sea

001

12233

Courtesy of RITE

Raw
Stack

Higher S/N ratio was obtained for the hydrophone survey.
Apparent higher resolution was obtained for the geophone survey .

Difference Section between A5H (high tide) and A1H(low tide)

Two Way Travel Time in sec

Land0Raw
StackA5 H

A1HDifference
A5H-A1HSea011223

3

Difference due to the tidal change was observed. Courtesy of RITE

25

Difference Section from low tide to high tide
Land0Sea
A6H - A1H0112233

A1H

Two Way Travel time in sec

26

A2H - A1H

A3H - A1H

A4H - A1H

A5H - A1H

Courtesy of RITE

Raw
StackLow

Tide

High

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Comparison between A(7/24) and B(8/31)

Two Way Travel time in sec

Land

A1H

B5H(same tide)
A1G

B5G00112233
Courtesy of RITE

Raw
Stack

Sea

Geophone section for Shooting B has better S/N than that for Shooting A.
→improvement of coupling of the geophones should be contribute.

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Index for 4D response evaluation
Kragh and Christie (2002)

Normalized RMS(NRMS)

Predictability(PRED)

200  RMS ai  bi 
NRMS RMS ai   RMS bi 100    ab    ab  PRED       aabb

ai, bi ：Amplitude bfr/aft injection

Φ：Cross correlation coefficient

NRMS = 0 : Identical
NRMS =200 : Reverse Polarity
NRMS =144 : Random Noise

PRED = 0 : No correlation
PRED =100 : ±100 % correlation

Repeatability Evaluation using
Crossplot between NRMS and PRED
Simulation

Real Data（Iwanohara Model, White Noise 25%)

（After kragh & Christie, 2001）

PRED

Black circle：All Area
Red circle: Injected Area
Half thePerfectCoincidence Amplitude

Polarity
Reversal

HRe
pe
at
ab

ility

L

S/N=0

NRMS

Current position of repeatability in average.
Calibration can increase the repeatability index.

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Observation of Micro-Seismic

Offshore
Tomakomai
M 0.6
From JMA

8/5 21:44 Offshore Tomakomai
Magnitude 0.6 Depth 103 km

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Offshore Tomakomai Micro-Seismic Event（after Rotation）
LandSeaZ（Vertical）
PY(Crossline)
HCF:20Hz
Relative amplitude
betweencomponents are notPreserved.

SX(Inline)

S
Courtesy of RITE

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Conclusions• Nearshore OBC observation was successfully
conducted for two months.
• High-quality repeated reflection records wereobtained and the effects of noise and tidalchange were analyzed.
• P-SV converted waves are considered to beobserved and further analysis will contribute tothe reservoir characterization.
• Small local earthquake observation indicatesthe possibility of the passive monitoring of CCS.

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Toward the Future• Permanent OBC system is a promising
tool for the nearshore CCS monitoring.
• Through more detailed and quantitative
study on the influence of noise and tide on
the 4D analyses, and P-SV analysis
toward the reservoir characterization,
development of practical procedure forthe permanent OBC monitoring can beachieved.

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Thank you very muchfor your kind attention

Toward Offshore CCS Seismic Monitoring－Development of Permanent OBC System－Akihisa (May-Q) Takahashi
JGI, Inc.