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Douma H.,ION Geophysical GXT Imaging Solutions | Vasconcelos I.,University of Edinburgh | Snieder R.,Colorado School of Mines
Journal of the Acoustical Society of America | Year: 2011

By analyzing correlation-type reciprocity theorems for wavefields in perturbed media, it is shown that the correlation-type reciprocity theorem for the scattered field is the progenitor of the generalized optical theorem. This reciprocity theorem, in contrast to the generalized optical theorem, allows for inhomogeneous background properties and does not make use of a far-field condition. This theorem specializes to the generalized optical theorem when considering a finite-size scatterer embedded in a homogeneous background medium and when utilizing the far-field condition. Moreover, it is shown that the reciprocity theorem for the scattered field is responsible for the cancellation of non-physical (spurious) arrivals in seismic interferometry, and as such provides the mathematical description of such arrivals. Even though here only acoustic waves are treated, the presented treatment is not limited to such wavefields and can be generalized to general wavefields. Therefore, this work provides the framework for deriving equivalents of the generalized optical theorem for general wavefields. © 2011 Acoustical Society of America. Source

Douma H.,ION Geophysical GXT Imaging Solutions | Haney M.,Boise State University
SEG Technical Program Expanded Abstracts | Year: 2011

We study the use of surface waves to invert for a near-surface shear-wave velocity model and use this model to calculate shear-wave static corrections. We invert both group-velocity and phase-velocity measurements, each of which provide independent information on the shear-wave velocity structure. For the phase-velocity we use both slant-stacking and eikonal tomography to obtain the dispersion curves. We compare models and static solutions obtained from all different methods using field data. For the Coronation field data it appears that the phase-velocity inversion obtains a better estimate of the long-wavelength static than does the group-velocity inversion. © 2011 Society of Exploration Geophysicists. Source

Van Wijk K.,Boise State University | Douma H.,Boise State University | Mikesell D.,ION Geophysical GXT Imaging Solutions | Haney M.,Boise State University
SEG Technical Program Expanded Abstracts | Year: 2011

Surface-wave tomography from the correlations of ambient noise records has provided a powerful tool to investigate the Earth's subsurface with new surface-wave information. Exploration surveys can benefit from inversion of these virtual surface waves, as well. Most commonly, correlations are performed on the vertical components of the wavefields, but here we use the crossterms of multicomponent data and show virtual surface wave recordings are less sensitive to artifacts from signal not in-line with the two stations. We illustrate this with a subsection of the Coronation data set and the Batholiths temporary seismic deployment, showing estimates of the Rayleigh wave and the consequent phase-velocity dispersion curve. © 2011 Society of Exploration Geophysicists. Source

Gaiser J.,ION Geophysical GXT Imaging Solutions | Gaiser J.,Geokinetics Inc. | Vasconcelos I.,ION Geophysical GXT Imaging Solutions | Vasconcelos I.,Schlumberger | And 2 more authors.
Geophysics | Year: 2012

In this study, elastic-wavefield interferometry was used to recover P- and S-waves from the 3D P-wave vibrator VSP data at Wamsutter field in Wyoming. S-wave velocity and birefringence is of particular interest for the geophysical objectives of lithology discrimination and fracture characterization in naturally fractured tight gas sand reservoirs. Because we rely on deconvolution interferometry for retrieving interreceiver P- and S-waves in the subsurface, the output fields are suitable for high-resolution, local reservoir characterization. In 1D media where the borehole is nearly vertical, data at the stationary-phase point is not conducive to conventional interferometry. Strong tube-wave noise generated by physical sources near the borehole interfere with S-wave splitting analyses. Also, converted P- to S-wave (PS-wave) polarity reversals occur at zero offset and cancel their recovery. We developed methods to eliminate tube-wave noise by removing physical sources at the stationary-phase point and perturbing the integration path in the integrand based on P-wave NMO velocity of the direct-arrival. This results in using nonphysical energy outside a Fresnel radius that could not have propagated between receivers. To limit the response near the stationary-phase point, we also applied a weighting condition to suppress energy from large offsets. For PS-waves, a derivative-like operator was applied to the physical sources at zero offset in the form of a polarity reversal. These methods resulted in effectively recovering P-wave dipole and PS-wave quadrupole pseudosource VSPs. The retrieved wavefields kinematically correspond to a vertical incidence representation of reflectivity/transmissivity and can be used for conventional P- and S-wave velocity analyses. Four-component PS-wave VSPs retrieve S-wave splitting in transmitted converted waves that provide calibration for PS-wave and P-wave azimuthal anisotropy measurements from surface-seismic data. © 2012 Society of Exploration Geophysicists. Source

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