Monitoring of CO2 injected at Ketzin using

3D time-lapse seismic data

Alexandra Ivanova1,2, Ursula Lengler1,Stefan Lüth1 and Christopher Juhlin2

(1) GFZ German Research Centre for Geosciences, Germany(2) Uppsala University, Sweden

EGU 2011 5.04.2011, Vienna, Austria

injection wellKtzi 201

observation well

Ktzi 200

observation wellKtzi 202

injection facility

CO2 Pilot Site

Geology of Ketzin

Structural model

V0 Caprock

V1 Aquifer

V0 Auitard

V2

Geology of Ketzin

Structural model

V0 Caprock

V1 Aquifer

V0 Auitard

V2

3D Repeat Survey

3D Baseline 2005: 41 Templates~14km2

3D Repeat 2009:20 Templates(after ~20 kilotons CO2 injected)

1 Template:5 lines, 240 geophones12 lines, 180 shotpoints

Start of acquisition 2009:25 Sep 2009

Last shotpoint:6 Nov 2009Ketzin

Repetability

2005baseline

2009repeat

Step:123456789

101112

13

141516171819202122232425

Original parameters:Read raw SEGD dataVertical diversity stackBulk static shift to compensate for source delay: 6 msExtract and apply geometryTrace edit and polarity reversalPick first breaks: offset range 300–500 mRemove 50-Hz noise on selected receiver locationsSpherical divergence correction: v2tBand-pass filter: Butterworth 7–14–150–250 HzSurface consistent deconvolution: filter 120 ms, gap 16 ms, white noise 0.1%Ground roll muteSpectral equalization 20–40–90–120 HzBand-pass filter:0–300 ms:15–30–85–125 Hz 350–570 ms:14–28–80–120 Hz 620–1000 ms: 2–25–70–105 HzZero-phase filterRefraction statics: datum 30 m, replacement velocity 1800 m /s, v0 1000 m/sTrace balance using data windowVelocity analysis: every 20th CDP in the inline and crossline directionResidual staticsNormal moveout correction: 50% stretch muteStackTrace balance: 0–1000 msFX-Decon: Inline and crossline directionsTrace balance: 0–1000 msMigration: 3D FD using smoothed stacking velocitiesDepth conversion: using smoothed stacking velocities

New parameters:

Bandpass filter: Butterworth 7-14-120-200 Hz

Spectral equalization20-35-80-110 HzBand-pass filter:0-300 ms:15-30-75-115 Hz350-570 ms:14-28-70-110 Hz620-1000 ms:12-25-60-95 Hz

Processing steps applied to 3D repeat compared with the original flow

Amplitude change anomaly over the CO2 injection site

low fold area for anomaly

1. max change in amplitude ~ amplitude of K2 reflection

2. anomaly ~ centered on injection well

3. positive polarity

VOLUMETRICS

Volumetric estimation of mass of the injected CO2 visible in seismic data will be performed using

- average values of CO2 saturation in reservoir obtained for every well of the Ketzin site witha) Pulsed Neutron-Gamma Well Logging;b) Multiphase Flow Modeling;

- average CO2 density calculated witha) measured temperature and pressure in reservoir at the injection site (in the injection well) to

the time of the repeat survey;b) from Multiphase Flow Modeling for every well of the Ketzin site.

Results show that we can see approximately the same quantity of the injected CO2 in the time-lapse seismic data :

a) Pulsed Neutron-Gamma Well Logging (~ 94%);b) Multiphase Flow Modeling (~91%).

Parameters for volumetric estimation

PARAMETER SOURCE

Time delay Velocity push-down

P-Velocities/CO2 and brine saturation

Petrophysics on samples from reservoir saturated with CO2 and brine

CO2 saturation in reservoir

Seismic time-lapse interpretation and:a) PNG Logging in 3 wellsb) Multiphase Flow Modelling

CO2 density in reservoir

a) Temperature and pressure in reservoir on the injection site

b) Multiphase Flow Modelling

Porosity Core analyses and logging

Time Difference for CDP bin Push-Down Effect:

dt = 2h * (1/v2 – 1/v1) => thickness h of CO2 plume

0 25 50 752500

2600

2700

2800

2900

3000

3100

3200

PNG

Modelling

100% brine

Velocitym/s

CO2 saturation%

v2

v1

Parameters for CO2 mass estimation per CDP bin

MOD MIN

MOD MAX

PNG MIN

PNG MAX

0

10

20

30

40

50

60

0.9-1.00.7-0.90.5-0.7

Ampl.Diff.

CO2 Saturation (%)

Ampl.Diff.

MOD MIN

MOD MAX

PNG MIN

PNG MAX

230

240

250

260

270

280

0.9-1.00.7-0.90.5-0.7

Ampl. Diff

CO2 Density (kg/m³)

Distribution of CO2 from 3D time-lapse observaons:

20.5 kTons 23 kTonsMass

of injected CO2 :

22.1-24.2 kTons

20 kTons 22.1 kTons

20.5 kTons 23 kTons

Min

Min

Max

Max

.

.

.

.

a) PNG Well Logging

Massof injected CO2 :

Repeat SurveyBeginning : 22.1 kTons Repeat SurveyEnd: 24.2 kTons

b) Multiphase Flow Modelling

Min

Min

Max

Max

.

. ..

20 kTons 22.1 kTons

23 kTons20.5 kTons

20 kTons

Min

1. Results of seismic interpretation and petrophysical data allowed a satisfactory CO2 mass estimation (91%-94% mass of injected CO2 to the time of the repeat survey) using values of CO2 saturation derived by

a) Pulsed Neutron-Gamma Logging;b) Multiphase-Flow Modeling;

and average CO2 density calculated with c) measured temperature and pressure in reservoir at the injected site

(in the injected well) to the time of the repeat survey;d) Multiphase Flow Modeling for every well of the Ketzin site.

2. Consequences for seismic data of CO2 effect on seismic velocities in reservoir rock (petrophysics) will be illustrated on synthetic seismic models.

3. ‘Predicted’ distributions will be used to generate synthetic seismic data that will be compared directly to seismic field data.

Summary and Outlook

Volumetric estimation based on velocity push-down

Structural model

V0 Caprock

V1 Aquifer

V0 Auitard

V2

Parameter Value

Receiver line spacing / number 96 m / 5

Receiver station spacing / channels 24 m /48

Source line spacing / number 48 m / 12

Source point spacing 24 m or 72 m

CDP bin size 12 m x 12 m

Nominal fold 25

Geophones 28 Hz single

Sampling rate 1 ms

Record length 3 sSource 240 kg accelerated

weight drop, 8 hits persource point

3D Acquisition Parameters

Seismic Interpretation

STACK

STACK MIGRATION

MIGRATION

Volumetric estimation based on velocity push-down

Structural model

V0 Caprock

V1 Aquifer

V0 Aquitard

Top aquifer

Bottom aquifer

Bottom aquitard

Volumetric estimation based on velocity push-down

Structural model

V0 Caprock

V1 Aquifer

V0 Aquitard

Reflectors in time migrated image

Top aquifer

Bottom aquifer

Bottom aquitard

ΔT

V2

CO2 Storage at Ketzin

Start of injection: 30th June, 2008

Food grade CO2 (99.9%)

~ 47,000 tons

Saline aquifer (Stuttgart Formation)

~ 620 m – 650 m

Juni 2008