Otway Basin Project Stage I: results of seismic
monitoring

M. Urosevic1,3, R. Pevzner1,3,
A.Kepic1,3, B. Gurevich1,3,
V. Shulakova2,3 and S. Sharma3,4
1 Curtin University, 2CSIRO, 3CO2CRC
4Schlumberger

With contributions from
C. Jenkins, K. Dodds, E. Caspari, M. Asgharzadeh, D. Sherlock,
R. Li, T. Dense, T. Daley, P. Wisman, C. Dupuis, A. Dzunic,
M. Leahy, J. Ennis-King
Schlumberger CO2 research crew
M. Verliac, A. J. Campbell, W. S. Leaney, L. Dahlhaus,Outline•

Stage I study: CO2 injection into a depleted gas reservoir•

Numerical simulations and pre base line tests•

Seismic monitoring program•

Data acquisition•

Results•

Final modelling•

Conclusions

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CO2CRC Otway Project (Victoria, Australia)
65 Kt

Stage II
injection
Paaratte

STAGE I: An 80/20 % of CO2/CH4 stream
produced from Buttress, transported
and injected into CRC-1 well (previous
gas production well)Stage I
injection
STAGE II: CO2/CH4 stream injected into
CRC-2 well(huff-and-puff) – up to 10 Kt.

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Naylor field, Otway• Unique test site (relevant for EHR)
• Infrastructure in place, natural CO2 accumulations• Opportunity to develop M&V strategies for several different
reservoirs• Current (phase I) CO2 storage involves deeper, depleted gas field(Naylor), highly porous and permeable formation• Opportunity to devise appropriate methodology that can beapplied to CO2 storage in depleted gas reservoirs

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The reservoir
Small, thin, heterogeneous and deep depleted gas reservoir, surrounded bycomplex faulting,
CO2/CH4 – mix injected and monitored with the most sensitive seismic
techniques
Pre-production 3D seismic data recorded in 2000
Naylor gas field
Strike direction

N-1
Waarre-C
500m

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CRC-1

Geophysical monitoring
Only time lapse (TL) seismic methods – great penetration, resolution

Issues:Expect small changes of the elastic properties of the reservoir due to
CO2/CH4 mix injection – saturation changes mainly (subtle TL signal)
Traditionally poor repeatability of land seismic surveys + accessibility,
environmental restrictions, cost, etc…

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Changes of rock properties due to fluid
substitution – homogeneous model

Relative impedance change

Velocity, km/s

3.5
3
2.5

Vp
Vs

2
1.5

0

0.2

0.4
0.6
Water saturation

0.8

1

1

0.95

0.9

0.85

0

0.2

0.4
0.6
0.8
Water saturation

Injection of CO2 in supercritical form into saline aquifer with 25%
porosity

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1

Modelling/predicting TL seismic effect due to
CO2/CH4 mix injection into Waarre-C
CRC-1

2.0

2.5

3.0

2700 3300 3900 4500

NAYLOR-1

Percentage different between preand post-injection

Pre-injection
Post-injection
2000

2500

3000

6000

9000

12000

0

5 10 15 20

0

5 10 15 20

0

5 10 15 20

0Percentage different between preand post-injection

Pre-injection
Post-injection

5 10 15 20

2.0

2050

2.5

3.0

3000 3500 4000 4500

2000

2500

3000

7000

9500 12000

0

5

10

15

0

5

10

15

0

5

10

15

0

5

10

15

IB IA

2025

2055

2075

2080

Gas Cap

2030

2035

GWC
Depth (m)2070

Waarre-C

AI ~3-6%

2065

Residual Gas

III III

Depth (m)Waarre-C

2060

2040

2045

2050

2055

2085

 (g/cm3)

Vp (m/s)Vs (m/s) AI (m/s*g/cm3)  (3.5%) Vp (2.3%) Vs (0.67%) AI (5.8%)2060

 (g/cm3)

Vp (m/s)Vs (m/s) AI (m/s*g/cm3)  (3.9%) Vp (1.6%) Vs (0.89%) AI (5.6%)

Computed changes in elastic properties including acoustic impedance for two wells. In
both cases impedance changes up to 6%; density dominated; very small change

For  AI~6% Max, R up to 15%. If NMRS < 20%...

Challenging...
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1D Modelling of CO2 “leak” scenario
Upward migration of CO2 into overlain strata (Paaratte saline aquifer 500 m above Naylor)

Assurance monitoring
15% Vp, 10% Rho and 5% Vs change

Sw=1
Sw=0.1 Sw=0.2 Sw=0.3

Very strong
TL effect due
to CO2
accumulationin Paaratte!

Depth~ 1100 m
Post-injection, Pp=12.5 MPa
Temp=55C ,Avg. Porosity=25%

Pre-production seismic

Paaratte saline
formation

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Post-injection, Pp=14MPa

2D numerical modelling of small amount of CO2 present in Paaratte

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2D sensitivity modelling of a CO2 “leak” into the Paarattesaline formation - model from reservoir simulation
1k

2k

3k

4k

5k

Supports the use of time lapse seismic for M&V
6k

7k

8k

9k

10 k

2.8 kmThe CO2 quantities shown in thousand tonnes. CO2 occupies thin layer, withsmall areal extent (less then Fresnel radius) - diffracted energy is roughly
proportional to CO2 volume; 30% of background noise.
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Application of diffracted wave analysis to leakage detection“Noisy” time lapse
signal

4 Kt of CO2 readily detectable
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How can we monitor Stage I injection?
Need TL surveys that can achieve:- High resolution- High sensitivity- Very good repeatability
Small target, small TL signal, traditionally poor
repeatability of land seismic surveys
Other limitations: accessibility, environmental
restrictions, cost, etc…

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Exploring around the site...

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Key issue: Repeatability versus TL signal
Weathering conditions: top soil (farming zone) + weathered clayrich zone on top of corrugated limestone
Seasonal variation of Water Table

0

1

2

3

4

5

05 06 07

Variable scattering with WT variation

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Pre baseline surveys
Repeatability and sensitivity tests(borehole and surface seismic program)

ZVSP

seismic
testline
line
2D
test
2Dseismic
seismic
test line

Soda’s Rd
OVSP
WVSP

Soda’s Rd tests
2Dseimic test line
Dry/wet conditions
Different sources

7 repeats

Objectives: establish repeatability, performance of different sources, related
energy loss, seasonal variation effects, survey logistics, accessibility,
acquisition geometry, duration, cost, etc.
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Pre-baseline borehole seismic tests
ZVSP – broad band
Soda’s road
Buttress - 1

Boggy Cr-1

Intra reservoir shale
detected

Boggy Ck - 1

Naylor-1
CRC-1
Naylor - 1-

HEMI 60

Naylor Sth -1

N-SouthSurfaceseismicOVSP

WVSP

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Pre baseline Z,O,WVSP surveys (2006) - very goodresults

ZVSP

ZVSP

All frequencies

Synthetic (post - production model)

Filtered
8-60HzVSP
Synthetic(pre-production)

Intra shale layer
detected

VSP~Post Production synthetic

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Pre baseline 2D reflection surveys (2006/7)
2006

2D MV seismic data low-passfiltered to match 3D seismic
Data
Data recorded
recorded with
with MV
M

Res.
sand

2000

2D line extracted from 3D seismic data – approximate location

Hemi 60, 10 x powerIt is always about the seismic sources…
MV- 6000 lb
WD – 1320 Kg

MB – 15000 lb

A concrete breaker !!!

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7 repeated 2D reflection surveys

MV-Wet-Jun2006

MV-Dry-Mar2007

WD-Wet-Jul2007

SourceNear‐Surface
Condition

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WD-Dry-Nov2008

VS-Wet-Jul2007

MB-Dry-Nov2008

Time‐lapse 3D data using different sources
3D surface seismic (extract) from 2000 to 2009
Pre -production

Post -injection

Pre -injection

2000

2009

2007
2008

Big Vib ; 3*60 Klb
Fold < 24

MB 9 Klb
Fold > 200

WD ~ 5 Klb
Fold > 100

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Big vs Small source

Crew size
Crew size

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Factors affecting TL seismic repeatability•

Positioning•

Non-repeatable, ambient noise•

Changes in source/receiver coupling•

Changes in near surface conditions•

Processing approach (cross-equalisation)

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Pre-base line 2D test surveys
Test1

Test2

Test3

Source Type

Weight Drop

Weight Drop

DateJune, 2007

November, 2008

Weather condition
Total Number of Source
positions
Total Number of Receivers
Source/Receiver Point Spacing,m
Number of Channels
Offset range, mReference Character

Wet

Dry

Mini Buggy
November,
2008
Dry

158

155

155

162

156

159

10/10

10/10

10/10

162
5‐1605
WD 2007156
5‐1545
WD 2008159
5‐1545
MB 2008

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2D repeatability tests – soil saturation and source typeRaw data (Soda’s Rd)

A) MB 2008

B) WD 2008

C) WD 2007
Offset, m

Dry

TWTT, ms

Dry

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Wet

2D repeatability tests – soil saturation and source type
Cross-equalized 2D stacked sections (Soda’s Rd)
MB 2008
WD 2008
WD 2007
Dry

TWTT, ms

Dry

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Wet

Repeatability of TL seismic surveys:
NRMS and S/N
NRMS  200%

RMS (a  b)
RMS (a )  RMS (b)where a and b are two surveys being compared [Kragh and Christie, 2002]

SN i 

[ g i ,i 1 ]MAX
1  [ g i ,i 1 ]MAX

where i is trace number, gi,i+1 is normalized cross-correlation function between i
and i+1 traces and [gi,i+1]MAX is its maximum value

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2D repeatability tests – soil saturation and source type
Cross-equalized 2D stacked sections (Soda’s Rd)
MB 2008
WD 2008
WD 2007
Dry

TWTT, ms

Dry

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Wet

2D repeatability tests along Soda’s Rd
A)

B)

NRMS: > 50%

C)

NRMS
NRMS, %S/N
100

NRMS(S/N, Freq, Refl, Window...)
10

1

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What is non-repeatability?
140
120

mb2008/wd2007
mb2008/wd2008
wd2008/wd2007

2
Noise / Signal

100
NRMS, %

2.5

mb2008/wd2007
mb2008/wd2008
wd2008/wd2007
Modelling

80
60

1.5

1

40

0.5

20
0

0

5

10
Signal/Noise15

20

Spectraldifference

0

0

50

100
NRMS, %

150

200

2D

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Seismic monitoring – Final program•Time lapse 3D surface seismic– Least sensitive and repeatable but provides coverage of entire reservoir andbeyond– Necessary for ‘assurance monitoring’ to detect loss of primary containment– No 4D effect expected in general•

Time lapse borehole seismic– CRC-1: 3DVSP with 3C geophones (Schlumberger’s VSI)
• Improved sensitivity and resolution relative to surface data, improved repeatability• More chance for direct CO2 monitoring, limited coverage– Naylor-1: Permanent downhole sensors (LBNL)• Potentially most sensitive and repeatable

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Many farmers, electric fences, 10000000 cows...

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TL : Simultaneous acquisition of 3D surface
and 3D
Survey Parameters
VSP

3D surface, VSP and GPS crew (2010)
SurveyLocation
Date

Cheap,
hey!
Baseline

Otway 3D
Otway Basin, Victoria, Australia
1) December 2007–January 2008
2) January 200929 Lines
2181 Points
10 Lines
873 Points

Number of Source Lines
Number of Source Points
Number of Receiver Lines
Number of Receiver Points
Number of Swath 2
Bin Size
10 m in-line by 10 m cross-line
Total Number of Bins
30821
Nominal Stacking Fold
100
Offset Range
50-2150 m
Receiver line orientation
West-East
Source Line Orientation
South-North (1-27 lines), WestEast (28-29 lines)
Source Parameters
Source Type
Weight Drop (concrete breaker) – 750 kg,
free fall from 1.2 m – 2008
IVI Mini-vibe 2009
Stacking fold4
Source Geometry
Source Line Spacing
100 m
Source point Spacing
20 m
Receiver Parameters
Receiver Type
10 Hz - geophones
Recording Pattern
Orthogonal cross-spread pattern(odd source line were recorded byfist 5 receiver lines, even sourcelines - by 6-10 receiver lines)
Receiver Line Spacing
100 m
Receiver Point Spacing
10 m
Recording Parameters
Record length4s
Sample Interval 1 ms – 2008, 2 ms - 2009
Recording Filters No filters were applied in the field

High resolution surveys: 10x10 bins, fold> 100

Monitor 1 &2

Source lines

Receiver lines

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TL ‐ 3D surface seismic acquisition geometry
2008 Receiver lines 1-5 activ
for odd shot lines,
receiver lines 6-10 active
for even shot lines
440 active geophones

2009 we had 880 channels
active at all times
Double the fold + muchstronger source than WD
Actual fold

3D VSP acquired simultaneously
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Sumer in Warrnambool....

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Basic 3D processing flow-chart
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•

Data input and correlation for 2009
Data equivalence and binning (bin size 10x10m)
Elevation statics (30 m, 1800 m/s)
Trace Editing
Bandpass filtering (7-10-150-160 Hz)
Spike and Burst Noise Attenuation
Automatic gain control (500 ms, applied before deconvolution andremoved after)
Spiking Deconvolution (minimum phase for 2008 and zero-phase for 2009)
Velocity Analysis (two iterations)
Residual Static Correction
Radon filter in cone window (AGC 500ms applied before and remove after)
FX deconvolution before stack
Normal Moveout Correction
CDP stackPost-processing (TV Whitening, FXY Deconvolution)
Explicit FD 3D Time Migration

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Key issue: Repeatability versus TL signal strength
Base-line, 2008

Monitor I, 20093D

Reservoir

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Post-injection, 2010

NRMS (60ms)
2008-20092008-20102009-2010
0

100

200

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Difference 08‐09, Xline 81
3D VSP model
difference

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Initial 3D TL result: difference 08-09, firstpass

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3D acoustic inversion
AI -2008

2008-2009

AI -2009

AI -2010

2008-20102009-2010b) AI -2009

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Difference volumes, reduced geometry

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2010-2009, full geometry

Very subtle TL signal: highly dependent on processing
flow and cross‐equalisation

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2009-2008, NRMS, 60 ms

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2010-2008, NRMS, 60 ms

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2010-2009, NRMS, 60 ms

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2009-2008
Small TL signal

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2010-2008
Small TL signal

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2010-2009
No TL signal

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Extended Stage I injection simulation
Time ofinjection

Naylor-1

Dummy well

CRC-1

Amount of
CO2/CH4
injected

2008
Base line

0 Kt

2009

33 Kt

2010

65 Kt

2011

100 KtCopyright CO2CRC

J. Ennis-King, 2010

Modelling of extended Stage I injection
2008-20092008-20112009-2010

AI in 2008

Identical colouring scheme

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Borehole seismic time-lapse studies

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TL 3D VSP imaging
3D VSP inserted into
surface seismic(baseline)

3D VSP
3D seismic

A. Campbell
Schlumberger

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Repeatability at Waare C level, surface
seismic vs VSP
2008-2010, 3D Surface seismic

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2008-2010, 3D VSPVSP repeatability
Processed data
2007

2010

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difference

VSP repeatability
Processed and cross-equalised data
2007

2010

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difference

3D VSP Time-Lapse analysis
3D VSP Baseline

3D VSP post‐injection

Cross-equalised

Difference - map
Naylor-1
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CRC-1

Assurance monitoring: Paaratte TL studies

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CO2 leak into Paaratte – very strong TL signal

Paaratte Level 1
Energy2008-2009

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2008-2010

Expected TL signal vs actual seismic
response in Paaratte
2008

2009‐20082010‐2009

Simulated response

7,000 t1 km

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Can we see less then 4,000-5,000?
TL section for 2000t of CO2

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Imaged difference section

Current work
Full 3C analysis
TL seismic anisotropy studies
Recovery of the full stiffness
Repeatability – near surface

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2D/3D TL VSP 3C studies
T, ms

FBPICK(ms)850
8005734000
750

P-wave azimuthal anisotropy

5733500
700
5733000
650
5732500
656500657000657500
UTM, Easting (m)“Stacking” velocity analysis

Stacking velocity, km/s

UTM, Norting (m)5734500

2.7
2.65
2.6
2.55
2.5
2.45

0

50

100

150

200

Azimuth,

250

300

o

-Elevation statics-First breaks approximated with hyperbola for each 15° azimuthal segment

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350

Converted S‐wave anisotropy
TL seismic
anisotropychanges – M&V methodology?
Splitshears analysis
2010

2007
Depth = 650.00 m

Fast

0

0

20

20

40

40

60

60
azimuth,oazimuth,oSlow

Depth = 650.00 m

80
100

100

120

120

140

140

160

160

180
0.9

0.95

1

1.05

1.1 1.15 1.2 1.25
apparent velocity, km/s

1.3

1.35

1.4

Polarisation
across-3D
Polarisation

80

180
0.9

5734500
0.95

1

1.05

1.1 1.15 1.2 1.25
apparent velocity, km/s

1.3

1.35

1.4

5734000
0
330

30

300

60
200
50 100 150
90

270

240

5733500

5733000

120

5732500
210

150
180

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656500657000657500658000658500
UTM, Easting (m)6590006595001590 mMASW for weathering characterisation
10 Hz frequency slice, WD2007, wet
X (m)

400
500

Velocity, m/s

600
700
800
900
1000
1100
1200
0

5

10

15

20
25
30
Frequency, Hz

35

40

45

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Conclusions•

Large number of unique TL data sets acquired (borehole and surface); inexpensive,
good quality, acquired with small crews•

Numerous scientific studies and advances achieved•

Opportunity for further long-term cutting edge research and international colaboration

Highlights•

Very good (post-stack) repeatability achieved combining weak and different source
types, thanks to high spatial data density and high fold•

CO2 upward migration (“Leak”) readily detectable with 3D TL seismic - no indication in
TL data (using diverse measurements and studies)•

Clear, unique TL signal from Waarre-C not observed (CO2 contained); very subtle TL
signal – sensitive to processing/cross-equalisation schemes (analysis still ongoing)•

VSP shows superior repeatability and sensitivity with respect to surface seismic (alsomeasure full wave field; possibility for development of alternative M&V methodologies )Copyright CO2CRC

CO2CRC Participants

Supporting Partners: The Global CCS Institute | The University of Queensland | Process Group | Lawrence Berkeley National Laboratory
Established & supported under the Australian Government’s Cooperative Research Centres Program