Time-lapse wave-equation migration velocity analysis

    Research output: Contribution to journalArticle

    6 Citations (Scopus)

    Abstract

    Time-lapse (4D) analysis of seismic data acquired at different stages of hydrocarbon production or gas/fluid injection has been very successful at imaging detailed reservoir changes. Conventional time-domain analysis of 4D data sets usually assumes a linear perturbation about a reference baseline earth model. However, this assumption is violated when production/injection significantly alters the subsurface generating large 4D velocity changes, time shifts, and complicated 4D wavefield coda, necessitating a more robust 4D analysis involving prestack wave-equation depth migration and velocity analysis. We address these situations by extending conventional 3D waveequation migration velocity analysis (WEMVA) based on one-way wave-equations and single-scattering theory to 4D velocity estimation using a "parallel" inversion approach involving parallel solution of two separate inversion problems. Recognizing that the 4D WEMVA strategy requires precomputed baseline/monitor image-difference volumes, we develop an approximate 4D WEMVA technique that replaces these differences with a single weight function derived from the smooth background time-lapse image difference. We demonstrate the usefulness of the parallel and an approximate 4D WEMVA approach using a synthetic time-lapse CO2 geosequestration experiment that requires inverting for a thin-layer velocity change derived from CO2 injection in an analogue North Sea reservoir. The parallel 4DWEMVA solutions generate an excellent highresolution velocity estimates, whereas the approximate methods recover lower-resolution estimates with magnitudes thatmust be rescaled through a post-inversion gradient line-search © 2013 Society of Exploration Geophysicists.
    Original languageEnglish
    Pages (from-to)S69-S79
    JournalGeophysics
    Volume78
    Issue number2
    DOIs
    Publication statusPublished - 2013

    Fingerprint

    wave equation
    Wave equations
    wave equations
    inversions
    fluid injection
    injection
    analysis
    gas injection
    time domain analysis
    North Sea
    Time domain analysis
    coda
    estimates
    Hydrocarbons
    monitors
    seismic data
    hydrocarbons
    Gases
    Earth (planet)
    scattering

    Cite this

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    title = "Time-lapse wave-equation migration velocity analysis",
    abstract = "Time-lapse (4D) analysis of seismic data acquired at different stages of hydrocarbon production or gas/fluid injection has been very successful at imaging detailed reservoir changes. Conventional time-domain analysis of 4D data sets usually assumes a linear perturbation about a reference baseline earth model. However, this assumption is violated when production/injection significantly alters the subsurface generating large 4D velocity changes, time shifts, and complicated 4D wavefield coda, necessitating a more robust 4D analysis involving prestack wave-equation depth migration and velocity analysis. We address these situations by extending conventional 3D waveequation migration velocity analysis (WEMVA) based on one-way wave-equations and single-scattering theory to 4D velocity estimation using a {"}parallel{"} inversion approach involving parallel solution of two separate inversion problems. Recognizing that the 4D WEMVA strategy requires precomputed baseline/monitor image-difference volumes, we develop an approximate 4D WEMVA technique that replaces these differences with a single weight function derived from the smooth background time-lapse image difference. We demonstrate the usefulness of the parallel and an approximate 4D WEMVA approach using a synthetic time-lapse CO2 geosequestration experiment that requires inverting for a thin-layer velocity change derived from CO2 injection in an analogue North Sea reservoir. The parallel 4DWEMVA solutions generate an excellent highresolution velocity estimates, whereas the approximate methods recover lower-resolution estimates with magnitudes thatmust be rescaled through a post-inversion gradient line-search {\circledC} 2013 Society of Exploration Geophysicists.",
    author = "Jeffrey Shragge and David Lumley",
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    language = "English",
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    }

    Time-lapse wave-equation migration velocity analysis. / Shragge, Jeffrey; Lumley, David.

    In: Geophysics, Vol. 78, No. 2, 2013, p. S69-S79.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Time-lapse wave-equation migration velocity analysis

    AU - Shragge, Jeffrey

    AU - Lumley, David

    PY - 2013

    Y1 - 2013

    N2 - Time-lapse (4D) analysis of seismic data acquired at different stages of hydrocarbon production or gas/fluid injection has been very successful at imaging detailed reservoir changes. Conventional time-domain analysis of 4D data sets usually assumes a linear perturbation about a reference baseline earth model. However, this assumption is violated when production/injection significantly alters the subsurface generating large 4D velocity changes, time shifts, and complicated 4D wavefield coda, necessitating a more robust 4D analysis involving prestack wave-equation depth migration and velocity analysis. We address these situations by extending conventional 3D waveequation migration velocity analysis (WEMVA) based on one-way wave-equations and single-scattering theory to 4D velocity estimation using a "parallel" inversion approach involving parallel solution of two separate inversion problems. Recognizing that the 4D WEMVA strategy requires precomputed baseline/monitor image-difference volumes, we develop an approximate 4D WEMVA technique that replaces these differences with a single weight function derived from the smooth background time-lapse image difference. We demonstrate the usefulness of the parallel and an approximate 4D WEMVA approach using a synthetic time-lapse CO2 geosequestration experiment that requires inverting for a thin-layer velocity change derived from CO2 injection in an analogue North Sea reservoir. The parallel 4DWEMVA solutions generate an excellent highresolution velocity estimates, whereas the approximate methods recover lower-resolution estimates with magnitudes thatmust be rescaled through a post-inversion gradient line-search © 2013 Society of Exploration Geophysicists.

    AB - Time-lapse (4D) analysis of seismic data acquired at different stages of hydrocarbon production or gas/fluid injection has been very successful at imaging detailed reservoir changes. Conventional time-domain analysis of 4D data sets usually assumes a linear perturbation about a reference baseline earth model. However, this assumption is violated when production/injection significantly alters the subsurface generating large 4D velocity changes, time shifts, and complicated 4D wavefield coda, necessitating a more robust 4D analysis involving prestack wave-equation depth migration and velocity analysis. We address these situations by extending conventional 3D waveequation migration velocity analysis (WEMVA) based on one-way wave-equations and single-scattering theory to 4D velocity estimation using a "parallel" inversion approach involving parallel solution of two separate inversion problems. Recognizing that the 4D WEMVA strategy requires precomputed baseline/monitor image-difference volumes, we develop an approximate 4D WEMVA technique that replaces these differences with a single weight function derived from the smooth background time-lapse image difference. We demonstrate the usefulness of the parallel and an approximate 4D WEMVA approach using a synthetic time-lapse CO2 geosequestration experiment that requires inverting for a thin-layer velocity change derived from CO2 injection in an analogue North Sea reservoir. The parallel 4DWEMVA solutions generate an excellent highresolution velocity estimates, whereas the approximate methods recover lower-resolution estimates with magnitudes thatmust be rescaled through a post-inversion gradient line-search © 2013 Society of Exploration Geophysicists.

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