RESOLUTION COMPARISON OF MINIMUM‐PHASE AND ZERO‐PHASE SIGNALS

Geophysics ◽  
1974 ◽  
Vol 39 (6) ◽  
pp. 826-833 ◽  
Author(s):  
M. Schoenberger

Despite their intuitive appeal, minimum‐phase wavelets are not the shortest wavelets achievable on a seismic section. For several amplitude spectra typical of processed seismic sections, both minimum‐phase and zero‐phase wavelets are presented. In each case, several measures of length reveal that the zero‐phase wavelet is shorter than the minimum‐phase wavelet corresponding to the same amplitude spectrum. Furthermore, the zero‐phase wavelet has smaller side lobes than the corresponding minimum‐phase wavelet. Synthetic seismograms were generated using both the zero‐phase and minimum‐phase signals as inputs. In each case, the seismogram generated with the zero‐phase input signal had better resolution. This relation is demonstrated quantitatively and is also visually obvious on the seismograms. In addition to comparing the wavelets’ resolution capabilities, the accuracies permitted in estimating reflection times were compared. The zero‐phase wavelets resulted in more accurate estimates of both reflection times and spacings.

1969 ◽  
Vol 59 (3) ◽  
pp. 1247-1258
Author(s):  
Abou-Bakr K. Ibrahim

abstract The amplitude spectrum obtained from Haskell's matrix formulation for body waves travelling through a horizontally layered crustal model shows a sequence of minima and maxima. It is known that multiple reflections within the crustal layers produce constructive and destructive interferences, which are shown as maxima and minima in the amplitude spectrum. Analysis of the minima in the amplitude spectra, which correspond to zero phase in the phase spectra, enables us to determine the thickness of the crust, provided the ratio of wave velocity in the crust to velocity under the Moho is known.


Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 288-290 ◽  
Author(s):  
Richard E. Duren ◽  
E. Clark Trantham

A controlled‐phase acquisition and processing methodology for our company has been described by Trantham (1994). He pointed out that it is careful attention to wavelet phase that leads to improved well ties and a more geologically accurate seismic image. In addition, we prefer zero‐phase wavelets on our seismic sections. For a given amplitude spectrum they have the simplest shape and the highest peak; further, the peak occurs at the reflection time of the event. This alignment is important since the seismic wavelet generally broadens with increasing depth with a zero‐phase wavelet remaining symmetrical about the event time. Our experience has been that a true zero‐phase section can be tied over the entire length of a synthetic trace without having to slide the synthetic trace to tie different time zones.


Author(s):  
Molong Duan ◽  
Keval S. Ramani ◽  
Chinedum E. Okwudire

This paper proposes an approach for minimizing tracking errors in systems with non-minimum phase (NMP) zeros by using filtered basis functions. The output of the tracking controller is represented as a linear combination of basis functions having unknown coefficients. The basis functions are forward filtered using the dynamics of the NMP system and their coefficients selected to minimize the errors in tracking a given trajectory. The control designer is free to choose any suitable set of basis functions but, in this paper, a set of basis functions derived from the widely-used non uniform rational B-spline (NURBS) curve is employed. Analyses and illustrative examples are presented to demonstrate the effectiveness of the proposed approach in comparison to popular approximate model inversion methods like zero phase error tracking control.


2009 ◽  
Vol 89 (6) ◽  
pp. 1032-1037 ◽  
Author(s):  
Corneliu Rusu ◽  
Jaakko Astola
Keyword(s):  

1985 ◽  
Vol 25 (1) ◽  
pp. 254
Author(s):  
T.J.C. Prudence ◽  
J. Flentri

The Kanpa 1A Vertical Seismic Profile (VSP) was conducted for Shell by Schlumberger and incorporated variable time and depth sampling, different source offsets and recording in cased and uncased hole. Processing was performed using Shell proprietary programs, with particular attention to:Editing and resampling of the data setSeparation of upgoing and downgoing waves using FK and median filtersComparison of gain recovery based on modelling the amplitude decay of direct arrivals with an averaging process (AGC)Sensitivity of the final VSP stack to blanking of residual tube wave noiseZero-phase whitening of the VSP traceStacked VSP traces for Kanpa 1A were compared with a zero-phase seismic section and synthetic seismogram at the well. The VSP/seismic match is good and, due to poor synthetic/seismic correlation, was the basis for the final seismic/well tie. Interpretation of deep VSP data enabled the estimation of formation boundaries below the total depth of the well.It is concluded that VSPs can be invaluable in establishing well ties where seismic is poor or when detailed correlation is required (e.g. stratigraphic traps). Reflectors "ahead of the bit" can be interpreted from VSPs based on assumed velocities and VSP/seismic tie, and the predicted thickness and seismic character of the target interval. A consistent field configuration is recommended for acquisition with attention to tube wave suppression and adequate spatial and temporal sampling. Previous processing experience is advantageous if quick and reliable VSP results are required for decisions while drilling.


Author(s):  
Eugeny V. Buldakov ◽  
Rodney Eatock Taylor ◽  
Paul H. Taylor

The problem of diffraction of a directionally spread focused wave group by a bottom-seated circular cylinder is considered from the view point of second-order perturbation theory. After applying the time Fourier transform and separation of vertical variable the resulting two-dimensional non-homogeneous Helmholtz equations are solved numerically using finite differences. Numerical solutions of the problem are obtained for JONSWAP amplitude spectra for the incoming wave group with various types of directional spreading. The results are compared with the corresponding results for a unidirectional wave group of the same amplitude spectrum. Finally we discuss the applicability of the averaged spreading angle concept for practical applications.


Geophysics ◽  
1984 ◽  
Vol 49 (4) ◽  
pp. 379-397 ◽  
Author(s):  
Bruce Gibson ◽  
Ken Larner

Predictive deconvolution is commonly applied to seismic data generated with a Vibroseisr® source. Unfortunately, when this process invokes a minimum‐phase assumption, the phase of the resulting trace will not be correct. Nonetheless, spiking deconvolution is an attractive process because it restores attenuated higher frequencies, thus increasing resolution. For detailed stratigraphic analyses, however, it is desirable that the phase of the data be treated properly as well. The most common solution is to apply a phase‐shifting filter that corrects for errors attributable to a zero‐phase source. The phase correction is given by the minimum‐phase spectrum of the correlated Vibroseis wavelet. Because no minimum‐phase spectrum truly exists for this bandlimited wavelet, white noise is added to its amplitude spectrum in order to design the phase‐correction filter. Different levels of white noise, however, produce markedly different results when field data sections are filtered. A simple argument suggests that the amount of white noise used should match that added in designing the (minimum‐phase) spiking deconvolution operator. This choice, however, also produces inconsistent results; field data again show that the phase treatment is sensitive to the amount of added white noise. Synthetic data tests show that the standard phase‐correction procedure breaks down when earth attenuation is severe. Deterministically reducing the earth‐filter effects before deconvolution improved the resulting phase treatment for the synthetic data. After application of the inverse attenuation filter to the field data, however, phase differences again remain for different levels of added white noise. These inconsistencies are attributable to the phase action of spiking deconvolution. This action is dependent upon the shape of the signal spectrum as well as the spectral shape and level of contaminating noise. Thus, in practice the proper treatment of phase in data-dependent processing requires extensive knowledge of the spectral characteristics of both signal and noise. With such knowledge, one could apply deterministic techniques that either eliminate the need for statistical deconvolution or condition the data so as to satisfy better the statistical model assumed in data‐dependent processing.


Geophysics ◽  
1991 ◽  
Vol 56 (7) ◽  
pp. 1058-1060 ◽  
Author(s):  
A. E. Barnes

Robertson and Nogami (1984) have shown that the instantaneous frequency at the peak of a zero‐phase Ricker wavelet is exactly equal to that wavelet’s average Fourier spectral frequency weighted by its amplitude spectrum. Bodine (1986) gave an example which shows this is also true for constant‐phase bandpass wavelets. Here I prove that this holds for any constant‐phase wavelet. I then develop an equation expressing this quantity as a function of propagation time through an attenuating medium. A corresponding equation is derived for the amplitude of the envelope peak. Taken together, these may aid in the analysis of seismic data as suggested by Robertson and Nogami (1984), Bodine (1986), and Robertson and Fisher (1988).


Geophysics ◽  
1987 ◽  
Vol 52 (1) ◽  
pp. 51-59 ◽  
Author(s):  
S. Levy ◽  
D. W. Oldenburg

The residual wavelet on a processed seismic section is often not zero phase despite all efforts to make it so. In this paper we adopt the convolutional model for the processed seismogram, assume that the residual phase shift can be approximated by a frequency‐independent constant, and use the varimax norm to generate an algorithm to estimate the residual phase directly. Application of our algorithm to reflectivities from well logs suggests that it should work in the majority of cases so long as the reflectivity is non‐Gaussian. An application of our algorithm to stacked data enhances the interpretability of the seismic section and leads to an improved match between the recovered relative acoustic impedance and a measured velocity log.


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