We know that achieving a zero phase wavelet is difficult, and thus it would be helpful if authors in this journal provide a comment on the phase of the data they are presenting in their interpretations. Zerophase data tend to provide sharper definition and less distortion between stratigraphic features in the subsurface, such as sand and shale layers. At the highest frequency, onehalf of the sampling rate, the phase increases by. First, there exists certain traditionalism in using seismic arrival times in the data processing. Zerophase wavelets are symmetrical in shape about zero time whereas nonzerophase wavelets are asymmetrical. Indeed, these assumptions are central to most avo and other quantitative work. Seismic processing publications 2019 applying the refraction migration method to image a deep interface in xinjiang, china yang shen, university of science and technology of china, jie zhang, geotomo. A zerophase signal is thus a linearphase signal for which the phaseslope is zero. Topics to be covered include statics corrections, filtering, velocity analysis, deconvolution, stacking and migration.
The seismicdata processing consists of velocity modeling, wavelet processing, and seismic inversion. Hence data processing today makes every effort to deliver the data in a zero phase condition. The minimum phase wavelet has a short time duration and a concentration of energy at the start of the wavelet. The objective of the statistical and deterministic deconvolution short course is to familiarize exploration seismologists about the theory and practice of seismic deconvolution and zero phase seismic processing.
When applied to the wavelet, the filter converts it to a zero delay spike. Characteristics of the phase digital signal processing. Differential time between two phases arrivals are particularly useful for many reasons, some listed here. A zero phase wavelet has the peaks or troughs centered on the reflecting interface. It removes the basic seismic wavelet the source time function modified by various effects of the earth and recording system from the recorded seismic trace and thereby increases temporal resolution. Phase in seismic data is simply known as the lateral time delay in the start of a reflection recording, and because it is amplitudeindependent, phase can be used as a good continuity indicator in poor reflectivity areas in the seismic data with a higher sensitivity to reflection discontinuity caused by pinch outs, faults, fractures, and other structural and stratigraphic seismic. Well data are gotten from rock samples and measurements at depth from a wellbore. Pdf seismic amplitude calibration for quantitative. Jones abstract conventional seismic data processing, whether it be prestack data conditioning or migration, is designed with the theory of pwave reflected energy inmind, for travel paths involving only a. Seismic data processing mostly takes into account the statistics inherent in the data to improve the data quality. Deconvolution during seismic processing can convert data of mixed phase to zero phase data, but is not always successful.
Seismic data processing investigations in geophysics, vol 2. Interpretive processing 329 seismic attributes 330 instantaneous attributes 332. Understanding seismic detection and resolution of high. Phase 349 phase rotation 349 alternate approaches to phase rotation 355.
Seismic data processing is a course designed to provide students with. Receiver deghosting removing gr accounts for the fact that the seasurface reflects seismic energy back into the water layer such that any seismic event is recorded twice. Figure 105a shows how the phase of this signal changes when it is shifted left or right. The reflection time for a zero phase wavelet is at the central peak or trough, so picking reflection times is much easier and accurate for zero phase wavelets. This requires measurement specifications which include large dynamic range, low harmonic distortion, low system noise levels, and a linear system response which is known in both amplitude and phase. To acquire skills in interpretation of 3d seismic data to enhance theoretical knowledge of seismic structural interpretation, stratigraphic interpretation, reservoir identification and evaluation, and horizon and formation attributes. Seismic migration is the process by which seismic events are geometrically relocated in either space or time to the location the event occurred in the subsurface rather than the location that it was recorded at the surface, thereby creating a more accurate image of the subsurface. Seismic data processing geos 469569 spring 2006 geos 469569 is a mix of digital filtering theory and practical applications of digital techniques to assemble and enhance images of subsurface geology. Seismic statistical and deterministic deconvolution course.
Ziolkowski advocates that seismic source signatures be measured rather than estimated when performing deconvolution. Nonzerophase wavelets are converted to zerophase wavelets to achieve the best resolution of the seismic data. Data conditioning encompasses a wide range of technologies designed to address numerous challenges in the processing sequencefrom data calibration and regularization. Jones abstract conventional seismic data processing, whether it be prestack data conditioning or migration, is designed with the theory of pwave reflected energy inmind, for travel paths involving only a single reflection. The seismic data processing consists of velocity modeling, wavelet processing, and seismic inversion. This is one reason why zerophase wavelets are usually output in seismic data processing. The solutions to these problems are to convert the mixed phase wavelet to zero phase in seismic processing or to extract the mixed phase wavelet, know its effects, and use it when modeling.
Wavelet polarity is divided to be 2 that is the europe standard and seg standard. There are two special types of phase spectra of specific interest. The reflection time for a zerophase wavelet is at the central peak or trough, so picking reflection times is much easier and accurate for zerophase wavelets. Most interpreters prefer to have seismic data processed to give a zero phase. This process is necessary to overcome the limitations of geophysical methods imposed by areas of complex geology. Deghosting and designature removing the seismic ghost. Understanding seismic detection and resolution of highfrequency sequences and systems tracts. Deconvolution during seismic processing can convert data of mixed phase to zerophase data, but is not always successful. That is, if p arrival is x sec, s phase is y sec, then we can approximate the sourcestation distance by x y 8 km only works for local distances. Special report of the seg technical standards committee1. For example, consider a waveform that is symmetrical around sample zero, and therefore has a zero phase. An ideal seismic source would be a spike maximum amplitude at every frequency, but the best practical one would be minimum phase.
Phase and polarity assessment of seismic data seg wiki. It is the shortest possible wavelet for any given spectrum. A seismic interpretation study should access the following data sets 2d or 3d seismic data cube. Applicationspecific seismic data conditioning and processing for confident imaging from the field to the final volume, seismic data goes through many processes and workflows. The intent of this acquisition step is to measure the signature with as much fidelity as possible. Digital filtering theory applies to virtually any sampled information in time e. Well data required for interpretation are wireline logs gamma ray logs, resistivity logs, porosity log, sonic logs, density logs and neutron logs or equivalent rock property model, check shot data. This is one reason why zero phase wavelets are usually output in seismic data processing. Zero phase wavelets are symmetrical in shape about zero time whereas non zero phase wavelets are asymmetrical.
A source signature was modelled to pass through the various processing stage, the resulting output converted to zero phase and the operator applied to the seismic data. How to remedy nonoptimal seismic data by seismic processing. The conmutator is zero just if w is an identity matrix, i. Advanced seismic interpretation is a course designed for graduate students. Along with amplitude and frequency, phase is a fundamental attribute of seismic data seismic data are usually processed to be zerophase, and we usually assume that the phase is stable in space and time. Timefrequency analysis of seismic data using local attributesa apublished in geophysics, 76, no. They are based on our tutorial datasets, which in turn came from the new zealand governments ministry of economic development under the open file system. Once the amplitude and phase spectra of the seismic wavelet are statistically estimated from the recorded seismogram, its leastsquares inverse spiking deconvolution operator, is computed using optimum wiener filters.
Thus, information about the phase spectrum of the observed signal is lost or substantially distorted. Shape the source wavelet to zero phase or minimum phase, depending on your application. Hence data processing today makes every effort to deliver the data in a zerophase condition. Pertaining to seismic data whose wavelet is symmetrical about zero time. Compensating for attenuation by inverse q filtering carlos a. Since some years the deterministic approach for processing shows many advantages. To localize frequency content in time, we have developed. Seismic attribute analysis provides information related to structure, stratigraphy, and reservoir properties. From the acoustic impedances produced by seismic inversion, the authors derive seismic. Extraction of wavelet from seismic using a well log to determine the phase.
Seismic data processing investigations in geophysics, vol. Commonly zero phase wavelet is used to interpretation seismic data because the wavelet has highest sn than other, maximum amplitude coincides with spike of reflection, and the pattern of wavelet is symmetry so picking horizon become easy. Compensating for attenuation by inverse q filtering. Relies on signal being in phase and noise being out of phase i.
How do we convert the seismic trace wavelet to zero phase. Dec 15, 2016 principles of seismic data interpretation m. Deghosting and designature removing the seismic ghost and. The limits of resolution of zerophase wavelets, geophysics, v. Zerophase filtering can be approximated by using a linearphase filter, a mixedphase filter which shifts component frequencies proportional to their frequency, and then delaying the time reference. Seismic data processing investigations in geophysics, vol 2 by ozdogan yilmaz author, stephen m. This barcode number lets you verify that youre getting exactly the right version or edition of a book. The society of exploration geophysicists the gas research institute. Center for wave phenomena colorado school of mines golden, co 80401, usa past support was received from. This results some aspects that would be improved during the seismic processing if broadband signals were acquired. If 1v1 2v2 shift in the phase of the reflected wave with 180 3. The solutions to these problems are to convert the mixedphase wavelet to zero phase in seismic processing or to extract the mixedphase wavelet, know its effects, and use it when modeling. The effect of low frequencies on seismic analysis nicolas martin and robertr. A minimum phase wavelet begins at the interface, whereas a wavelet with a phase of 90 has the interface centered on the zero crossing between a peak and a trough or vice versa.
When interpreting seismic data, it is important to realize that the actual subsurface geology is always being viewed through the filter of the seismic wavelet. This modern introduction to seismic data processing in both exploration and global geophysics demonstrates practical applications through real data and tutorial examples. Seismic interpretation an overview sciencedirect topics. Zero phase data tend to provide sharper definition and less distortion between stratigraphic features in the subsurface, such as sand and shale layers. This attitude to the phase spectra of seismic signals can be explained by several facts. The overall objective of this course is to introduce entry level andor junior geophysicists and geoscientists to the essential acquisition and technical processing concepts and principles that form the basis for value added seismic applications in exploration, field appraisal, and reservoir management. Dec 15, 2016 principles of seismic data processing m.
Note that in seismic, the cosine wave is the sinusoid of reference since it is a maximum at time. My preferred way of doing this ive been working in seismic data processing and analysis for over 20 years now is. The objective of the statistical and deterministic deconvolution short course is to familiarize exploration seismologists about the theory and practice of seismic deconvolution and zerophase seismic processing. Hentz, 2004, highfrequency sequence stratigraphy from seismic sedimentology. If you wanted to go to zerophase the process would be much the same instead of a minimum phase equivalent of the source signature, you would calculate the zerophase version and work with that the antialias filter would also need to be zero phase, of course. A seismic signal frequency division processing method comprises the steps of i utilizing an earthquake acquisition device to obtain a seismic signal. The third and final stage of the hierarchy of seismic interpretation is seismic attribute analysis taner and sheriff, 1977. Although it is difficult to ever argue against using physical measurements, the expense and difficulty of the measurements. Cn104216014a seismic signal frequency division processing. Known zero phase well synthetics and vertical seismic profiles vsps can be compared with local surface seismic data to. Seismic statistical and deterministic deconvolution course objective. Seismic phases and 3d seismic waves main seismic phases.
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