An Efficient Multiscale Method for An Efficient Multiscale Method for Time-Domain Waveform TomographyTime-Domain Waveform Tomography

C. BoonyasiriwatC. Boonyasiriwat11, P. Valasek, P. Valasek22, P. Routh, P. Routh22,,W. CaoW. Cao11, G.T. Schuster, G.T. Schuster11, and B. Macy, and B. Macy22

11 Department of Geology and Geophysics, University of Utah Department of Geology and Geophysics, University of Utah22 Seismic Technology Development, ConocoPhillips Seismic Technology Development, ConocoPhillips

OutlineOutline

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• IntroductionIntroduction

• Efficient multiscale waveform tomographyEfficient multiscale waveform tomography

• Synthetic data resultsSynthetic data results

• 1D Model1D Model

• 2D Model2D Model

• Field data resultsField data results

• ConclusionsConclusions

Cons:Cons:

Hamming window is a leaky, low-pass filter.Hamming window is a leaky, low-pass filter.

Arbitrary frequency bands were used.Arbitrary frequency bands were used.

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IntroductionIntroduction

Pros and cons of the multiscale method proposed Pros and cons of the multiscale method proposed by Bunks et al. (1995):by Bunks et al. (1995):

Pros:Pros:

Partially overcome the local minima problem.Partially overcome the local minima problem.

OutlineOutline

3

• IntroductionIntroduction

• Efficient multiscale waveform tomographyEfficient multiscale waveform tomography

• Synthetic data resultsSynthetic data results

• 1D Model1D Model

• 2D Model2D Model

• Field data resultsField data results

• ConclusionsConclusions

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Efficient Multiscale Waveform TomographyEfficient Multiscale Waveform Tomography

We propose:We propose:

• more efficient low-pass filtersmore efficient low-pass filters

• a strategy for choosing optimal frequency bandsa strategy for choosing optimal frequency bands

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Efficient Low-Pass FiltersEfficient Low-Pass Filters

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Hamming

Blackman-Harris

Ricker

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Strategy for Choosing Optimal FrequenciesStrategy for Choosing Optimal Frequencies

Image from Sirgue and Pratt (2004)

Strategy for Choosing Optimal Frequency BandsStrategy for Choosing Optimal Frequency Bands

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b) Amplitude Spectrum of Ricker wavelet

Strategy for Choosing Optimal Frequency BandsStrategy for Choosing Optimal Frequency Bands

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OutlineOutline

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• IntroductionIntroduction

• Efficient multiscale waveform tomographyEfficient multiscale waveform tomography

• Synthetic data resultsSynthetic data results

• 1D Model1D Model

• 2D Model2D Model

• Field data resultsField data results

• ConclusionsConclusions

1D Model1D Model

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c) Velocity Contribution in Space Domain

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d) Velocity Contribution in Wavenumber Domain

1D Model1D Model

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2D Model2D Model

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OutlineOutline

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• Goals of studyGoals of study

• Overview and introductionOverview and introduction

• Efficient multiscale waveform tomographyEfficient multiscale waveform tomography

• Synthetic data resultsSynthetic data results

• 1D Model1D Model

• 2D Model2D Model

• Field data resultsField data results

• ConclusionsConclusions

515 Shots480 Hydrophones

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Gulf of Mexico DataGulf of Mexico Data

Reconstructed VelocityReconstructed Velocity

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Kirchhoff Migration ImagesKirchhoff Migration Images

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Comparing CIGsComparing CIGs

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OutlineOutline

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• Goals of studyGoals of study

• Overview and introductionOverview and introduction

• Efficient multiscale waveform tomographyEfficient multiscale waveform tomography

• Synthetic data resultsSynthetic data results

• 1D Model1D Model

• 2D Model2D Model

• Field data resultsField data results

• ConclusionsConclusions

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ConclusionsConclusions

• An efficient MWT method was developed.An efficient MWT method was developed.

• Increased efficiency is achieved by using Increased efficiency is achieved by using efficient low-pass filters and optimal frequency efficient low-pass filters and optimal frequency bands.bands.

• The strategy for choosing frequency bands was The strategy for choosing frequency bands was validated in both 1D and 2D synthetic model validated in both 1D and 2D synthetic model experiments.experiments.

• Marine data results are promising.Marine data results are promising.