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

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CORPORATIONCORPORATIONPrestack 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

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

Vassiliou, GeoEnergy

September 2007

CORPORATIONCORPORATION

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.

Well to Seismic TieWell to Seismic Tie

CORPORATIONCORPORATIONPost-stack Rock PropertiesPost-stack Rock Properties

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Pay sand has lower Vp / Vs and P- imp

Pay sand has lower Vp / Vs and P- imp

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

Pre-Stack Rock PropertiesPre-Stack Rock Properties

CORPORATIONCORPORATIONWorkflowWorkflow

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Input PSTM Gather (Left) and Modeled GatherInput PSTM Gather (Left) and Modeled Gather

CORPORATIONCORPORATIONStarting and Final ModelsStarting and Final Models

DensityDensityInitialInitial FinalFinal

Vp Vp InitialInitial FinalFinal

Vs Vs InitialInitial FinalFinal

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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.

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.

Applications of Pre-Stack InversionApplications of Pre-Stack Inversion

CORPORATIONCORPORATIONFull Stack Amplitude ExtractionFull Stack Amplitude Extraction

ARB LINE

ARB LINE

ARB LINE

ARB LINE

2000’2000’2000’2000’

Well EWell EWell EWell E

Well CWell CWell CWell C

Well BWell BWell BWell B

Well AWell AWell AWell A

Well FWell FWell FWell F

Well DWell DWell DWell D

Well 3Well 3Well 3Well 3

CORPORATIONCORPORATIONFull StackFull Stack

Main Producing FieldMain Producing Field

Horizon AHorizon AHorizon AHorizon A

Horizon BHorizon BHorizon BHorizon B

WELL E WELL C WELL BWELL A

WELL F

Cross Section

CORPORATIONCORPORATION5-20 Angle Stack5-20 Angle Stack

Main Producing FieldMain Producing Field

Horizon AHorizon AHorizon AHorizon A

Horizon BHorizon BHorizon BHorizon B

WELL E WELL C WELL BWELL A

WELL F

Cross Section

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Arbitrary Line-Interpreted Lithology CubeArbitrary Line-Interpreted Lithology Cube

Main Producing FieldMain Producing Field

Horizon AHorizon AHorizon AHorizon A

Horizon BHorizon BHorizon BHorizon B

WELL C WELL BWELL A

WELL F

Cross Section

WELL E

CORPORATIONCORPORATIONVp/Vs VolumeVp/Vs Volume

ARB LINE

ARB LINE

ARB LINE

ARB LINE

2000’2000’2000’2000’

Well EWell EWell EWell E

Well CWell CWell CWell C

Well BWell BWell BWell B

Well AWell AWell AWell A

Well FWell FWell FWell F

Well DWell DWell DWell D

Well 3Well 3Well 3Well 3

CORPORATIONCORPORATIONDZPDZP

ARB LINE

ARB LINE

ARB LINE

ARB LINE

2000’2000’2000’2000’

Well EWell EWell EWell E

Well CWell CWell CWell C

Well BWell BWell BWell B

Well AWell AWell AWell A

Well FWell FWell FWell F

Well DWell DWell DWell D

Well 3Well 3Well 3Well 3

CORPORATIONCORPORATIONDZSDZS

ARB LINE

ARB LINE

ARB LINE

ARB LINE

2000’2000’2000’2000’

Well EWell EWell EWell E

Well CWell CWell CWell C

Well BWell BWell BWell B

Well AWell AWell AWell A

Well FWell FWell FWell F

Well DWell DWell DWell D

Well 3Well 3Well 3Well 3

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

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 DifferencesInversion Technique Differences

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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

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

Inversion Technique Differences con’t.Inversion Technique Differences con’t.

CORPORATIONCORPORATIONConclusionsConclusions

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

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

CORPORATIONCORPORATIONAcknowledgementsAcknowledgements

Seismic Data Courtesy of Seitel Seismic Data Courtesy of Seitel