Pdf the conventional synthetic seismogram is created with a sonic and a density log. Crains petrophysical handbook synthetic seismograms. Find file copy path fetching contributors cannot retrieve contributors at this time. However, sonic logs as observed in many studies, often have poor quality or even absent in some cases. Computational effort increases rapidly with number of layers, frequency of source, phase velocity range of interest. Synthetic seismogram is a seismic trace created from sonic and density logs and it. Schuster geology and geophysics department university of utah. Strange but true stories of synthetic seismograms cseg. Position of the particle at time t origin 0 origin u x x position of the particle at time t displacement u ux. Pupils reinforce knowledge of terms such as epicentre and focus before analysing a seismogram for the 2008 market rasen earthquake in lincolnshire.
A synthetic seismogram is created to simulate seismic data acquisition in your computer. Display the synthetic on seismic lines going through, or near, the well until the line that best fits the synthetic is found. This fits in with the aqa a specification textbook. Our product is widely used in the exploration community in support of prospect development and evaluation. Rapid generation of synthetic seismograms in layered media by vectorization of the algorithm robert a phinney on. Basics of exploration seismology and tomography pdf 20p. The use of edited or modeled log data as input is highly recommended. Pdf generation of pseudosynthetic seismograms from. In the synthetic generation program, run a frequency scan, which calculates traces with a range of frequency filters. A synthetic seismogram is the result of forward modelling the seismic response of an input earth model, which is defined in terms of 1d, 2d or 3d variations in physical properties. As discussed, if a vsp is available for a particular well, a synthetic is not needed. During odp leg 165, sonic and density logs were collected. A 3channel seismogram from our commercial seismograph, showing the start times of the primary p and secondary s waves and the vibration end time c.
At what time did the p waves begin time in seconds. Synthetic seismogram calculation using the reflectivity method. In creating a synthetic seismogram, syntool permits the interpreter to tie time data the seismic data to depth data the well data by integrating over the velocity profile. Grid dispersion in generating finitedifferences synthetic.
The first trace should include high frequencies, to show the best possible time resolution of events. The matching process involves simulating a seismic trace from well logs and user parameters waveform, frequency, phase, then manually aligning the simulated trace with the field traces in the vicinity of the well. Seismogram definition of seismogram by merriamwebster. Can i generate a synthetic seismogram only with a sonic log. Each person or small group can stand about 23 m from the geophone and jump up and down. It represents the idealize trace that should be observed with the seismic method at the location of the well. The reflection coefficients for the trace were simply computed with the recursion.
Synthetic seismogram from the sonic log, assuming constant density, normal incidence, no multiples or reverberations and no absorption, a synthetic seismic trace was created. Synthetic seismogram generation what we have stated above is that conversion of energy p to s takes place at oblique incidence of the incident waves. Seismograph, instrument that makes a record of seismic waves caused by an earthquake, explosion, or other earthshaking phenomenon. Seismogram definition of seismogram by the free dictionary. If the cell size becomes too large in comparison with wavelength of the source signal, waves disperse with increasing traveltime. Get the distance from the epicenter from the graph you made earlier. Basics of exploration seismic experiments and data processing, basics of traveltime tomography and basics of waveform tomography. A frequency domain synthetic seismogram generation was implemented for a sample interval of 1 ms and a maximum modeled time of 8s. An example of the output seismogram for a stomp test is shown in figure 4. What we have stated above is that conversion of energy p to s takes place at oblique incidence of the incident waves. Synthetic seismogram free synthetic seismogram software. The seismogram basics activity is a worksheet for students to complete. After parsing and reformatting the logs, each log was examined individually, looking for obviously erroneous values in velocity or.
Ihave extractedseismic wavelet from synthetic data from different offset traces and examinedthe variation in the extracted waveformand analyzedthe effect of directivity, angle dependence of reflection coefficients and noise. Pdf generation of pseudosynthetic seismograms from gamma. Generation of highresolution synthetic seismogram from image. A seismograph detects movement in the earths crust, translating that. We may emphasize this aspect as normal for the incident wave there will be no conversion of energy, and for angles of incidence less than 10 or 12 degrees, there is no detectable conversion. Click to view pdf version with images, as originally presented in aapg explorer. Three different synthetic seismograms created with identical well logs and wavelets figure 6 should theoretically be identical, however we observe that the first two traces are reasonably similar but the third trace, the one that uses flow b. Seismology and the earths deep interior seismogram interpretation history of traveltimeshistory of traveltimes harrold jeffreys and keith bullen 1940, jb remarkable accuracy for teleseismic travel times below 1%.
Primary waves are compressional longitudinal waves that are the first to arrive at the seismograph. The geological modeling procedure generally involves the generation of a. You have to define all the steps you want first, irrespective of what language you code it in and that is well outside of the scope of a matlab forum if you havent done it already. Simple flowcharts are giventoindicate the logical flowand the program output. In this volume i describe programs used for synthetic seismogram generation. The general purpose of this study is to test whether the generation of synthetic wavefields for geodynamically derived seismic veloc ity models is suited to provide. Without a seismograph, there would be no seismogram. The upper trace is the raw seismogram, while the lower trace is lowpass filtered with a cutoff of 4 hz. Generating synthetic seismogram with matlab essc india. The production process of synthetic seismogram is a complicated, multiple factors should be considered to make high quality synthetic seismogram, because these factors are intertwined, some even contain each other, restrict the synthetic seismogram making precision of varying degrees3. When generating synthetic seismograms with the sole purpose of matching the statistical characteristics of data, one would like to do as well as these approaches. A seismograph is a piece of equipment that records earthquake movements. Compute complete synthetic seismograms based on the following required elements.
This assessment covers the history and function of seismographs. This work is a case study for the transformation of resistivity logs to pseudo sonic logs for the generation of pseudo synthetic seismogram. Acknowledgments i am grateful to many graduate students, including sebastiano damico, ali fatehi, julia kurpan, filipe leyton, oner sufuri, yan xu, hongfeng yang, and kathy zou, at department. Interpreting seismograms worksheet teaching resources. In hydrocarbon exploration this is used to provide a tie between changes in rock properties in a borehole and seismic reflection data at the same location. Integration of thomsonhaskell reflectivity matrix terms over angle of incidence and then fourier transform to obtain seismogram.
The present work is an effort to develop a technique by which such a seismogram can be. At what time did the s waves begin time in seconds. Elizabeth winkler, wsj, mathematics pioneer ingrid daubechies has more barriers to break, 24 jan. Comparison of seismic reflection data to a synthetic seismogram in a volcanic apron at site 9531 thomas funck2 and holger lykkeandersen3 abstract the volcanic apron of gran canaria at site 953 is characterized by numerous, closely spaced reflectors, allowing a highresolution stratigraphic correlation. The terms seismograph and seismometer are often used interchangeably.
This is normally done over some limited interval in the well, probably centered on the reservoir target. Rapid generation of synthetic seismograms in layered media by vectorization of the algorithm. Artificially generated seismic waves recorded during seismic surveys are used to collect data in oil and gas prospecting and engineering. The unknown physical properties of the earth beneath a seismic survey are known properties at a wellbore pwave acoustic velocity and bulk density. Synthetic seismogram an overview sciencedirect topics. Synthetic seismograms and seismic waveform modeling. Generate a synthetic seismogram through synpak using the best available data for the sonic, density, and timedepth chart. The synthetic seismic can be compared with the seismic trace actually measured at the well to improve the picking of seismic horizons, and to.
Generating a synthetic seismogram can be a very complicated process. A technique for improving pseudosynthetic seismograms generated. These two items go hand in hand and are essential for the study of earthquakes. Basics of exploration seismology and tomography pdf 20p covered topics. Travel times in the earth ray paths, phases and their. His industrial career included 17 years with amoco in calgary and tulsa 19761993. Figure shows that the waveforms of the mcs traces within the sediment section differ from the waveforms within the basement. Droxler3 abstract onedimensional synthetic seismograms are constructed from velocity and density measurements taken during ocean drilling program odp leg 165 at sites 998, and 1001. Seismogram definition is the record of an earth tremor by a seismograph. The synthetic seismogram is a seismic trace that has been contructed from well log data. A more narrow definition used by seismic interpreters is that a synthetic seismogram, commonly called a synthetic, is a direct onedimensional model of acoustic energy traveling through the layers of the earth. Research to improve the quality of synthetic seismogram.
Write down your data in the box to the right of each seismogram. Table 2 lists the magnitude and sign of the static time shift applied to align the synthetic and. The record of an earth tremor made by a seismograph. Synthetic seismograms, synthetic sonic logs and synthetic. For a successful assessment, focus on wave measuring and device origin. A seismogram is a visual record that is created by a seismograph. Rapid generation of synthetic seismograms in layered media. In order to obtain a finitedifference synthetic seismogram, the finite earth model must be subdivided into cells.
Dziewonski and anderson 1981, preliminary reference. Since a real seismogram is a record of lagrangian motion, we will use the lagrangian description. The process of generating synthetics and calibrating them to real seismic data is as. Extraction of wavelet from a trace assuming minimum phase assumption. Popeye gsand log responses and synthetic seismogram ties v 1. In conventional method, both sonic and density logs are used for generating synthetic seismograms, but they are highly sensitive to borehole conditions rather. The depthcorrected logs were then obtained from the borehole research group at the lamontdoherty earth observatory. Generation of the synthetic seismograms was performed using the landmark syntool module. A synthetic seismogram is the fundamental link between well data and seismic data, and it is the main tool along with a vertical seismic profile vsp, if available that allows geological picks to be associated with reflections in the seismic data. Whatever method is used for generating the wavelet, it generates the. The l g phase is a ringy sequence of arrivals with group velocities of 3.
Lines held the nsercpetrocanada chair in applied seismology at. I dont have a density log, but i need to generate the synthetic seismogram in order to perform the seismic well tie. If desired, one can save the seismogram from each make your own earthquake shaking experiment and print it out to document the earthquake. Synthetic seismogram calculation using the reflectivity. The synthetic seismograms facilitate correlation of singlechannel seismic scs reflection profiles acquired aboard the cape hatteras and maurice ewing with. Generation of pseudo synthetic seismograms from gammaray well logs of highly radioactive formations article pdf available in pure and applied geophysics 1761 september 2018 with 271 reads. A cloudbased synthetic seismogram generator implemented using windows azure article pdf available in earthquake science 265. Seismographs record the amplitude and frequency of seismic waves and yield information about the earth and its subsurface structure. The synthetic seismogram is generated by convolving the reflectivity derived from. Recent examples on the web her wavelets have helped geologists analyze seismograms and neuroscientists read mri images of brain activity. The result of one of many forms of forward modeling to predict the seismic response of the earth.