Reconditioning Seismic Data to Improve Carbonate Stratigraphic Interpretation

and Reservoir Characterization,Fullerton Field, West Texas

by Hongliu ZengBureau of Economic Geology

John A. and Katherine G. Jackson School of GeosciencesThe University of Texas at Austin

Carbonate Earth Mode:How Much Can Seismic Data Help?

Earth ModelSeismic Data

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Presentation Outline

• Value of seismic data as seen in petrophysical analysis• Why seismic data needs reconditioning before

interpretation?• Basic seismic data conditioning (phase adjustment and

high-frequency enhancing)• Advanced seismic data conditioning (progressive, model-

based inversion)

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Fullerton Seismic Data (2-D & 3-D)

Labrador

Southful

Phase 1

Phase 2

2 km

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Synthetic Seismogram (Cal/Mon 1)

Tubb

Abo

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Velocity (ft/s)15000 25000

Porosity0 10 20

De

pth

(ft

)

Ve

loc

ity

(ft

/s)

Porosity

1.2 104

1.4 104

1.6 104

1.8 104

2 104

2.2 104

2.4 104

0 0.05 0.1 0.15 0.2 0.25

y = 20690.30758 - 28524.84397x R= 0.8542726121

6800

6880

6960

7040

7120

7200

7280

7360

Tubb

Wichita

Zone1

Zone2

Abo

Log Velocity vs. Log Porosity(FCU2723)

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Zone 2Zone 1

Wichita

Tubb

Abo

Up. St.

Original Seismic Poorly Tied toLog Lithology/Porosity

DT

1000

1100

ms

1 km

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Basic Data Conditioning

• High-frequency enhancing - Original data are dominated by low frequencies - Boosting high-frequency components improves seismic resolution (even in a price of reducing S/N ratio)

• Adjust seismic phase to 90º- Standard zero-phase wavelet is not ideal for

lithologic interpretation of seismically thin beds - 900-phase data resemble the impedance section, which conditions amplitude to lithology

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

200

300

400

500

600

700

800

900

100

00

Interpretive Advantage of90º-Phase Wavelet(Fullerton Carbonates)

Zone 2

Zone 1

Wichita

Tubb

940

1020

ms

980

1060

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

High-frequency Enhancing(Spectral Balancing)

0 60 120 Hz

Zone 2

Zone 1

Wichita

Tubb

940

1020

ms

980

1060

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Data Conditioning ImprovesResolution and Well-Seismic Tie

Original data

ReconditionedData after phaseShifting and high-Frequency enhancing

Zone 2Zone 1

Wichita

Tubb

Abo

Up. St.

Zone 2Zone 1

Wichita

Tubb

Abo

Up. St.1000

1100

ms

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Amplitude as Indicator of PHIH (L2100/Wichita)

PHIH (well) Amplitude

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

PHIH (well) Amplitude

Amplitude as Indicator of PHIH(L2200/Zone 2)

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Advanced Data Conditioning

• Seismic data are limited in frequency (<100 Hz) and Resolution (10 ms or 100 ft)

• The only source of high-frequency information beyond seismic is well logs

• Use of well logs as soft constrain may significantly improve resolution (2 ms or 20 ft)

• Tool: model-based inversion (Hampson-Russell, Jason, CGG, etc.)

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Model-Based InversionInitial ModelImpedance Logs

SeismicInverted Impedance

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Challenges in Building Initial Model

• Impedance values between wells are interpreted• Correlation of well logs are characterized by

uncertainties of various degrees• Correlation surfaces may not be accurate beyond wells• First initial model is always not optimal

Tubb

Up. St.

Zone1

Zone2

Wichita

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Well Correlation vs. Real Seismic

Tubb

Up. St.

Zone1

Zone2

Wichita

Tubb

Up. St.

Zone1

Zone2

Wichita

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Progressive Inversion

• Build multiple initial models and do multiple inversions• Start from the most prominent and reliable geologic

boundaries and seismic horizons, adding additional horizons from intermediate inversion results

• Use more and more horizons to build better initial model, resulting in better inversion with higher resolution.

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Start from Best Horizons

Tubb

Up. St.

Zone1

Zone2

Wichita

Tubb

Up. St.

Zone1

Zone2

Wichita

Abo

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Progressive Inversion(First Round)

Tubb

Abo

Tubb

Abo

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Tubb

Abo

Tubb

Abo

Progressive Inversion(Second Round)

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Tubb

Abo

Progressive Inversion(Third Round)

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Improvement in Resolution

Seismic 3rd-Round Inversion

100ft

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology

Summary

• Original seismic data are often not optimal for geologic interpretation and need reconditioning

• Basic data conditioning (1) corrects seismic phase and (2) enhance high-frequency components in the data, improving resolution to 100 ft

• Advanced data conditioning combines geologic interpretation and seismic data in a progressive, model-based inversion procedure, further improving resolution to 20 ft

H. Zeng; UL/PTTC May 2003 Workshop, Bureau of Economic Geology