Wavefield Extrapolation in Pseudo-depth Domain

Handle URI:
http://hdl.handle.net/10754/205792
Title:
Wavefield Extrapolation in Pseudo-depth Domain
Authors:
Ma, Xuxin
Abstract:
Wave-equation based seismic migration and inversion tools are widely used by the energy industry to explore hydrocarbon and mineral resources. By design, most of these techniques simulate wave propagation in a space domain with the vertical axis being depth measured from the surface. Vertical depth is popular because it is a straightforward mapping of the subsurface space. It is, however, not computationally cost-effective because the wavelength changes with local elastic wave velocity, which in general increases with depth in the Earth. As a result, the sampling per wavelength also increases with depth. To avoid spatial aliasing in deep fast media, the seismic wave is oversampled in shallow slow media and therefore increase the total computation cost. This issue is effectively tackled by using the vertical time axis instead of vertical depth. This is because in a vertical time representation, the "wavelength" is essentially time period for vertical rays. This thesis extends the vertical time axis to the pseudo-depth axis, which features distance unit while preserving the properties of the vertical time representation. To explore the potentials of doing wave-equation based imaging in the pseudo-depth domain, a Partial Differential Equation (PDE) is derived to describe acoustic wave in this new domain. This new PDE is inherently anisotropic because the use of a constant vertical velocity to convert between depth and vertical time. Such anisotropy results in lower reflection coefficients compared with conventional space domain modeling results. This feature is helpful to suppress the low wavenumber artifacts in reverse-time migration images, which are caused by the widely used cross-correlation imaging condition. This thesis illustrates modeling acoustic waves in both conventional space domain and pseudo-depth domain. The numerical tool used to model acoustic waves is built based on the lowrank approximation of Fourier integral operators. To investigate the potential of seismic imaging in the pseudo-depth domain, examples of zero-offset migration are implemented in pseudo-depth domain and compared with conventional space domain imaging results.
Advisors:
Alkhalifah, Tariq
Committee Member:
Ketcheson, David I. ( 0000-0002-1212-126X ) ; Mai, Paul Martin ( 0000-0002-9744-4964 )
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Program:
Earth Sciences and Engineering
Issue Date:
11-Dec-2011
Type:
Thesis
Appears in Collections:
Theses; Physical Sciences and Engineering (PSE) Division; Earth Science and Engineering Program

Full metadata record

DC FieldValue Language
dc.contributor.advisorAlkhalifah, Tariqen
dc.contributor.authorMa, Xuxinen
dc.date.accessioned2012-01-31T09:23:20Z-
dc.date.available2012-01-31T09:23:20Z-
dc.date.issued2011-12-11en
dc.identifier.urihttp://hdl.handle.net/10754/205792en
dc.description.abstractWave-equation based seismic migration and inversion tools are widely used by the energy industry to explore hydrocarbon and mineral resources. By design, most of these techniques simulate wave propagation in a space domain with the vertical axis being depth measured from the surface. Vertical depth is popular because it is a straightforward mapping of the subsurface space. It is, however, not computationally cost-effective because the wavelength changes with local elastic wave velocity, which in general increases with depth in the Earth. As a result, the sampling per wavelength also increases with depth. To avoid spatial aliasing in deep fast media, the seismic wave is oversampled in shallow slow media and therefore increase the total computation cost. This issue is effectively tackled by using the vertical time axis instead of vertical depth. This is because in a vertical time representation, the "wavelength" is essentially time period for vertical rays. This thesis extends the vertical time axis to the pseudo-depth axis, which features distance unit while preserving the properties of the vertical time representation. To explore the potentials of doing wave-equation based imaging in the pseudo-depth domain, a Partial Differential Equation (PDE) is derived to describe acoustic wave in this new domain. This new PDE is inherently anisotropic because the use of a constant vertical velocity to convert between depth and vertical time. Such anisotropy results in lower reflection coefficients compared with conventional space domain modeling results. This feature is helpful to suppress the low wavenumber artifacts in reverse-time migration images, which are caused by the widely used cross-correlation imaging condition. This thesis illustrates modeling acoustic waves in both conventional space domain and pseudo-depth domain. The numerical tool used to model acoustic waves is built based on the lowrank approximation of Fourier integral operators. To investigate the potential of seismic imaging in the pseudo-depth domain, examples of zero-offset migration are implemented in pseudo-depth domain and compared with conventional space domain imaging results.en
dc.language.isoenen
dc.titleWavefield Extrapolation in Pseudo-depth Domainen
dc.typeThesisen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberKetcheson, David I.en
dc.contributor.committeememberMai, Paul Martinen
thesis.degree.disciplineEarth Sciences and Engineeringen
thesis.degree.nameMaster of Scienceen
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