Prestack waveform inversion an onshore application in the us gulf coast
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Prestack Waveform Inversion: an Onshore Application in the US Gulf Coast. August Lau, Chuan Yin, Mike Greenspoon, Apache Corp; Anthony Vassiliou, GeoEnergy September 2007. Well to Seismic Tie.

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Prestack waveform inversion an onshore application in the us gulf coast

Prestack Waveform Inversion: an Onshore Application in the US Gulf Coast

August Lau, Chuan Yin, Mike Greenspoon, Apache Corp; Anthony Vassiliou, GeoEnergy

September 2007


Well to seismic tie
Well to Seismic Tie US Gulf Coast

Well-to-seismic tie: zero-offset synthetic and PSTM final stack. Displayed panels are (L to R): gamma-ray log, resistivity log, sonic log, bulk density log, full-stack overlaid with zero-offset synthetic, cross-correlation of the synthetic to surface seismic.



Pay sand has lower Vp / Vs and P- imp US Gulf Coast

Pre-Stack Rock Properties

Sand with Pay has Lower Vp / Vs Ratio and Lower P-impedance


Workflow
Workflow US Gulf Coast



Vp US Gulf Coast

InitialFinal

Vs

InitialFinal

Density

InitialFinal

Starting and Final Models


Applications of pre stack inversion
Applications of Pre-Stack Inversion US Gulf Coast

  • Estimation of Vp, Vs, density, Zp, Zs and their uncertainties for fluid and lithology discrimination

  • Through calibration and interpretation, thickness estimation, net to gross estimation, porosity estimation

  • Interpretation of small-scale or localized features, such as narrow channels, slump faults, etc.


Full stack amplitude extraction

Well F US Gulf Coast

Well 3

Well A

2000’

Well B

Well D

Well C

Well E

ARB LINE

Full Stack Amplitude Extraction


Full stack
Full Stack US Gulf Coast

Main Producing Field

Cross Section

WELL F

WELL A

WELL B

WELL C

WELL E

Horizon A

Horizon B


5 20 angle stack
5-20 Angle Stack US Gulf Coast

Main Producing Field

Cross Section

WELL F

WELL A

WELL B

WELL C

WELL E

Horizon A

Horizon B


Arbitrary line interpreted lithology cube
Arbitrary Line-Interpreted Lithology Cube US Gulf Coast

Main Producing Field

Cross Section

WELL F

WELL A

WELL B

WELL C

WELL E

Horizon A

Horizon B


Vp vs volume

Well F US Gulf Coast

Well 3

Well A

2000’

Well B

Well D

Well C

Well E

ARB LINE

Vp/Vs Volume


Well F US Gulf Coast

Well 3

Well A

2000’

Well B

Well D

Well C

Well E

ARB LINE

DZP


Well F US Gulf Coast

Well 3

Well A

2000’

Well B

Well D

Well C

Well E

ARB LINE

DZS


Inversion Technique Differences US Gulf Coast

Major Differences between Pre-stack Waveform Inversion applied to gathers and angle-stack inversions:

  • Pre-stack waveform inversion is applied directly on gathers with NMO removed, preserving all amplitude, phase, offset information

  • Pre-stack waveform inversion is seismic data driven. Angle stack inversion commonly well log driven

  • Assuming long enough acquisition cable, pre-stack waveform inversion estimates directly Vp, Vs, density


Inversion Technique Differences con’t. US Gulf Coast

  • Pre-stack waveform inversion can work with either only primary reflections or with both primary and multiple reflections

  • Pre-stack waveform inversion applied directly on gathers does not have to deal with the NMO stretch effect for long cables

  • Pre-stack waveform inversion makes use of interval velocities.

  • Pre-stack waveform inversion applied on gathers is not sensitive to starting low frequency Vp / Vs / density model


Conclusions
Conclusions US Gulf Coast

  • Pre Stack Inversion is a faster, cheaper, and more accurate method than traditional well-based inversion techniques

  • Various output volumes can be calibrated with well control for net pay estimations

  • Prospects can be qualified with multi-cube interpretation

  • A detailed geologic input model is not necessary to produce results


Acknowledgements
Acknowledgements US Gulf Coast

  • Seismic Data Courtesy of Seitel


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