The Marchenko method represents a constructive technique toobtain Green�s functions between the acquisition surface andany arbitrary point in the medium. The process generally involvessolving an inversion starting with a direct-wave Green's function from the desired subsurface position, which is typicallyobtained using an approximate velocity model. In thisstudy, we first propose to formulate the Marchenko method inthe time-imaging domain. We recognize that the traveltimeof the direct-wave Green�s function is related to the Cheop�straveltime pyramid commonly used in time-domain processingand can be readily obtained from the local slopes of thecommon-midpoint (CMP) gathers. This observation allowsus to substitute the need for a prior velocity model with thedata-driven slope estimation process. Moreover, we show thatworking in the time-imaging domain allows for the specificationof the desired subsurface position in terms of vertical time,which is connected to the Cartesian depth position via the timeto-depth conversion. Our results suggest that the prior velocitymodel is only required when specifying the position in depthbut this requirement can be circumvented by making use of thetime-imaging domain and its usual assumptions. Provided thatthose assumptions are satisfied, the estimated Green�s functionsfrom the proposed method have comparable quality tothose obtained with the knowledge of a prior velocity model.
Presentation Date: Wednesday, October 17, 2018
Start Time: 1:50:00 PM
Location: 211A (Anaheim Convention Center)
Presentation Type: Oral
The Biot theory provides a general framework for describing the seismic response of porous media. Proper boundary conditions must be specified for the following three cases: the elastic-poroelastic interface, the acoustic-poroelastic interface and the poroelastic-poroelastic interface for accurate modeling and inversion of seismic data. In this study, we first review the expressions for reflection coefficients for all three cases from plane-wave analysis. We subsequently benchmark the first two cases against spectral element method (SEM) forward modeling to verify and ensure consistency between finite-frequency wavelets. We show with numerical examples, that both methods lead to comparable results within frequency range between 5Hz and 80Hz, which is of relevance to exploration seismology.
Presentation Date: Monday, October 15, 2018
Start Time: 1:50:00 PM
Location: Poster Station 15
Presentation Type: Poster
van Vossen, Robbert (Utrecht University, The Netherlands) | Trampert, Jeannot (Utrecht University, The Netherlands) | Curtis, Andrew (Schlumberger Cambridge Research and The University of Edinburgh, United Kingdom) | Laake, Andreas (WesternGeco, United Kingdom)
Source and receiver amplitude equalization is necessary when their behavior changes with location within a given survey. Preferably, these corrections are performed in the early stages of processing. However, existing techniques which account for these effects, such as surface-consistent deconvolution, are applicable to primary reflection data only. Therefore, these techniques require prior processing. We developed an alternative method to compensate for source and receiver perturbations which has the advantage of being purely a preprocessing step. It is applicable to the whole seismic trace, and no assumptions are imposed on the subsurface. The method is based on reciprocity of the medium response. As a result of reciprocity, differences between normal and reciprocal recordings can be attributed to the source and receiver perturbations. We applied this technique to single-sensor data acquired in Manistee County, Michigan. At this site, near-surface conditions vary, and this significantly affects the data quality. The application of the equalization procedure led to a significant improvement in signal-to-noise ratio, on both prestack and poststack data.
Spetzler, Jesper (Delft University of Technology, The Netherlands) | Jocker, Jeroen (Delft University of Technology, The Netherlands) | Smeulders, David (Delft University of Technology, The Netherlands) | Trampert, Jeannot (Utrecht University, The Netherlands)
Ray theory is inadequate to explain the behavior of finite-frequency wave propagation in media with structures smaller in size than wavelength and the Fresnel zone. In such complex structures, wave diffraction effects are important. By performing an ultrasonic wave experiment, a newly developed theory for finite-frequency wave propagation is successfully validated. The presented wave theory has a large potential in high-resolution seismic crosswell and VSP tomographic experiments.