Extraction of wavelet from seismic using a well log to determine the phase. Processing, inversion, and interpretation of seismic data, issue 10, volume 1 issue 10 of investigations in geophysics seismic data analysis. Phase and polarity assessment of seismic data seg wiki. Seismic processing attempts to enhance the signal to noise ratio of the seismic section and remove the artifacts in the signal that were caused by the seismic method. 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. Zerophasing of seismic data request pdf researchgate. In summary, the scientists have proven that the second way. The desired output wavelet is designed to preserve the. In addition to providing excellent structural images, the dense sampling of a 3d survey makes it possible to map reservoir quality and the distribution of oil and gas. The archetypal oscillation, the sine wave, describes the displacement y of a point around a circle. Do the brightdim spots or phase changes show the appropriate zero phase character. The vsp can also give insight into seismic wave propagation and provide processing and interpretive. Reflections on the deconvolution of land seismic data.
Seismic data processing investigations in geophysics, vol. Histogram matching seismic wavelet phase estimation a thesis. 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. Use the latest seismic processing software to prepare the data for interpretation. Although it is difficult to ever argue against using physical measurements, the expense and difficulty of the measurements. Is the phase change structurally consistent and at the same level as the flat spot. It involves the geometric repositioning of return signals to show an event layer boundary or other structure where it is being hit by the seismic wave rather than where it is picked up. Vertical seismic profiling has been a useful measurement to obtain rock properties velocity, impedance, attenuation, anisotropy in depth as well as to provide a seismic image of the subsurface. Source designature sgf is the process of collapsing the farfield signature into a desired output wavelet generally a zerophase wavelet. Zerophase data tend to provide sharper definition and less distortion between stratigraphic features in the subsurface, such as sand and shale layers. This is the ideal of seismic imaging flat surface and collocated sources and receivers in practice, multifold, offset recording is used, and zerooffset section is obtained by extensive data processing. Thus, information about the phase spectrum of the observed signal is lost or substantially distorted. Most seismic sources do not generate a zero phase pulse, because that implies output before time zero.
Aspects of seismic reflection data processing social sciences. So my question is how do we convert the seismic trace wavelet to zero phase which is in mixed phase. Histogram matching seismic wavelet phase estimation jiangbo yu approved. Most chapters in the book are followed by problem sets. Seismic data acquisition and processing springerlink. Coppens, 1999 and from the cd signal processing in geosciences f. Amplitude and phase spectrum seismic acquisition and processing summary workflows zero phase and minimum phase wavelets normal and reverse polarities. Migration, display and other advanced processing techniques are available and essential to the complete utilization of the seismic data. Note that in seismic, the cosine wave is the sinusoid of reference since it is a maximum at time. We need a zerophase wavelet that can directly correspond to the time taken to travel in a given media. Filters preserving phase in this chapter, linear phase and zero phase filters are defined and discussed.
Have the seismic data being used been converted to zero phase. Pdf processing of seismic reflection data using matlab. Zero phasing converts the signal to one with zerophase. For instance an air gun source generates a minimum phase pulse. However, it is typically unknown, and assumed to be both broad band and zero phase. Geol463 seismic method the only method giving complete picture of the. Practical solutions to integrated oil and gas reservoir analysis, pp. For several amplitude spectra typical of processed seismic sections, both minim. Deconvolution during seismic processing can convert data of mixed phase to zero phase data, but is not always successful. The preprocessing involved correctly identifying the source type and deriving a suitable zero phase designature filter for each. When interpreting seismic data, it is important to realize that the actual subsurface geology is always being viewed through the filter of the seismic.
This short book is for students, professors and professionals interested in signal processing of seismic data using matlab. Waves that are not in phase are typically described by the angular difference between them, such as, 180 degrees out of phase. Topics covered in this book include basic structural interpretation and mapmaking. 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. In their method, first they average the amplitude spectrum of the observed traces and use it as the amplitude spectrum of the seismic wavelet. 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. Another goal of deconvolution is to produce a wavelet with a simple phase character, ideally a zerophase wavelet, which is the same for every trace in the seismic dataset. A new approach for extracting the amplitude spectrum of. Many of the seismic methods in popular use today go back to the work of some of the great scientists of past centuries. This course is an introductory course designed for individuals who work with seismic data.
Pertaining to seismic data whose wavelet is symmetrical about zero time. Alfred wegeners book the origin of continents and oceans, 1915, and his works. Covers the basic ideas and methods used in seismic processing, concentrating on the fundamentals of seismic imaging and deconvolution. Aug 21, 2003 3d seismic data have become the key tool used in the petroleum industry to understand the subsurface. Deconvolution attempts to compress the wavelet, thereby increasing the resolution of the seismic data. Dec 23, 2015 ali added it dear sir ozdogan, i need to your book seismic data processing, if you give me one copy hard or soft. A raft of new geophysics books recently, mostly from cambridge, prompts this look at six volumes on seismic analysis the more quantitative side of interpretation. This modern introduction to seismic data processing in both exploration and global geophysics demonstrates practical applications through real data and tutorial examples. Hence data processing today makes every effort to deliver the data in a zerophase condition. Topics to be covered include statics corrections, filtering, velocity analysis, deconvolution, stacking and migration. Early in our careers as geophysicists, most of us took at least one course on seismic signal analysis where we were taught that standard wiener deconvolution converts the minimumphase source wavelet in our seismic data to a wavelet with a phase spectrum that is zero and an amplitude spectrum that is broad and flat. In some cases, a suitable filter could not be derived, in which case a statistical zerophasing would be performed poststack. Providing this broad band, zero phase wavelet is the processing goal of deconvolution. The seg standard for display of a zero phase wavelet is shown in figure p6.
Filters preserving phase introduction to digital filters. This is one reason why zero phase wavelets are usually output in seismic data processing. Only minimal processing would be required if we had a perfect acquisition system. When the estimated constant phase of the statistical wavelet is consistent with the. A zero phase signal is thus a linear phase signal for which the phase slope is zero. According to assumption 5, the seismic wavelet is always minimum phase, which is a causal signal and its energy is zero before time zero. The farfield signature estimation can be improved by making use of nearfield hydrophone recordings. Bibliography processing of seismic reflection data using. How do we convert the seismic trace wavelet to zero phase. Fundamentals of signal processing seismic data analysis. This on line course introduces signal processing tools currently used in geophysics. Request pdf zerophasing of seismic data by zerophasing the. Unfortunately, this goal is rarely met and the typical wavelet that remains in fully processed seismic data is mixedphase.
Many of the processing techniques single and multichannel, involve an operand seismic trace and an operator filter. Zero phase wavelets are symmetrical in shape about zero time whereas non zero phase wavelets are asymmetrical. This is one reason why zerophase wavelets are usually output in seismic data processing. A typical marine farfield source signature in a wavelet calculator. Zerophase signals are discussed in sheriff and geldart, 1995, section. In such cases, it is necessary to convert the source wavelet into its minimum phase equivalent. Seismic data processing investigations in geophysics, vol 2. Source designature sgf is the process of collapsing the farfield signature into a desired output wavelet generally a zero phase wavelet. A zerophase signal is thus a linearphase signal for which the phaseslope is zero. We need a zero phase wavelet that can directly correspond to the time taken to travel in a given media. Understanding seismic detection and resolution of high.
The disadvantages again are that the results are bandlimited and a wavelet is not used, so the input seismic must be zero phase. 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. The desired output wavelet is designed to preserve the total energy of the farfield signature. Seismic processing migration pre stack migration migration is a tool used in seismic processing to get an accurate picture of underground layers. Nonzerophase wavelets are converted to zerophase wavelets to achieve the best resolution of the seismic data.
If the source wavelet in the seismic trace is not minimum phase, the deconvolution produces unstable results. Hence data processing today makes every effort to deliver the data in a zero phase condition. The seg standard for display of a zerophase wavelet is shown in figure p6. Is a phase change visible at the edge of the anomaly. Known zero phase well synthetics and vertical seismic profiles vsps can be compared with local surface seismic data to. Last year, i did a roundup of six books about seismic interpretation.
Compensating for attenuation by inverse q filtering. As well as phase, amplitude levels were also matched across all surveys. 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. Seismic inverse q filtering is a data processing technology for enhancing the resolution of reflection seismology images. There must be an important processing procedure to do so. How can i determine the phase of processed 2d seismic data. Zero phase data tend to provide sharper definition and less distortion between stratigraphic features in the subsurface, such as sand and shale layers. The stepbystep demo of the full reflection seismic data processing. Compensating for attenuation by inverse q filtering carlos a. Acquisition, processing, and interpretative challenges caused by the local environment of the cook inlet are both logistical and geological in nature. Aspects of seismic reflection data processing social.
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. Seismic data processing is a course designed to provide students with. Early in our careers as geophysicists, most of us took at least one course on seismic signal analysis where we were taught that standard wiener deconvolution converts the minimum phase source wavelet in our seismic data to a wavelet with a phase spectrum that is zero and an amplitude spectrum that. Seismic inversion, in geophysics is the process of transforming seismic reflection data into a.
You only need three pieces of information to describe it perfectly. 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. Effect of wavelet frequency on seismic response which display do you prefer. Seismic processing 3 reflection seismology spectral. Those individuals may be processing geophysicists, seismic interpreters or acquisition specialists.
We can use minimum phase wavelet for acquisition and during processing convert to zero phase. As we know the mixed phase data would not give the real twtt through the medium. A minimumphase wavelet is onesided it is zero before t 0. Note that in seismic, the cosine wave is the sinusoid of reference since. 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. Linear phase filters symmetric impulse responses a linear phase filter is typically used when a causal filter is needed to modify a signals magnitudespectrum while preserving the signals timedomain waveform as much as possible. University of houston in partial ful llment of the requirements for the degree master of science by jiangbo yu may 2012. By setting the phase to zero, they obtain a zerophase wavelet. It is the shortest possible wavelet for any given spectrum.
Generally speaking, there are three phases of a seismic project. Buy seismic data processing investigations in geophysics, vol 2 on free shipping on qualified orders. Seismic amplitude is an invaluable daytoday tool for graduate students and industry professionals in geology, geophysics, petrophysics, reservoir engineering, and all subsurface disciplines making regular use of seismic data. Deconvolution during seismic processing can convert data of mixed phase to zerophase data, but is not always successful. First, there exists certain traditionalism in using seismic arrival times in the data processing. Deghosting and designature removing the seismic ghost. Non zero phase wavelets are converted to zero phase wavelets to achieve the best resolution of the seismic. The purpose of seismic processing is to manipulate the acquired data into an image that can be used to infer the subsurface structure. Zerophase filtering of a minimumphase wavelet seg wiki. Seismic data have been collected and used successfully in hydrocarbon exploration in the cook inlet basin since the 1950s.
Wavelet polarity is divided to be 2 that is the europe standard and seg standard. Another example for employing phase in seismic processing is shown by mitrofanov and priimenko. Deghosting and designature removing the seismic ghost and. Deconvolution during seismic processing can convert data of mixed phase to zerophase. Acquisition processing interpretation in this chapter we concentrate on interpretation, but it is hard to ignore the importance of the other phases. Thenafter finding zs, and shifting the phase of operator by 90deg. The researchers have given a comparison between amplitude and phase spectra in detecting pinchouts of the oil and gas spectrum and thin layers in their paper. The conmutator is zero just if w is an identity matrix, i. 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. Review and cite seismic data processing protocol, troubleshooting and. Seismic response was computed trace by trace from the impedance grid converted to time. Updated processing methods, technologies enhance vintage. Frequencydomain filtering involves multiplying the amplitude spectrum of the input seismic trace by that of the filter operator.
Seismic data acquisition, processing, and interpretation. The advantages of this method are its simplicity, short computation time, and robustness in the presence of noise, making it good for quick and preliminary inversions. Work with 2d, 3d, 4d, multicomponent or full azimuth from land, marine, seabed or borehole. The desired output processing wavelet is derived from a zero phase equivalent of the modeled instrument response which is tapered to match the natural decay of the farfields amplitude spectrum. A simple application of fourier analysis is in the design of zerophase frequency filters, typically in the form of bandpass filtering. We know that achieving a zerophase 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. It has been elaborated both from the book signal processing for geologists and geophysicists j. So we produce the amplitude spectrum,z and the average seismic spectrum, s in order to obtain operator,o. The signature looks pretty close to a minimum phase wavelet, as you might expect. Ziolkowski advocates that seismic source signatures be measured rather than estimated when performing deconvolution.
Zerophase wavelets are symmetrical in shape about zero time whereas nonzerophase wavelets are asymmetrical. Seismic data acquisition generation of artificial seismic signals on. Seismic processing 3 reflection seismology spectral density. Q is the anelastic attenuation factor or the seismic quality factor, a measure of the energy loss as the seismic wave moves. This attitude to the phase spectra of seismic signals can be explained by several facts.
22 453 99 335 680 227 128 330 117 596 982 416 600 76 75 144 69 1552 1401 927 157 1607 410 117 1045 1196 1496 188 295 377 385 633 1432 349 68 1444 1119