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Text (Revised 05.12.2013)

1. 41 RadExPro seismic software www radexpro com PS PP velocities Semblance Display Gather Display STCK Display CVS Display Supergather Input velocity Output velocity Semblance Single velocity function n t Use file Browse Database picks 1 Database grid Browse Velocity domain Velocity type 6 Tine Depth RM C Interval Now switch to the Input velocity tab switch on the Database picks option and select the same velocity pick object that you have specified for the output This will ensure that you can interrupt your work and then run the flow once again to continue from the same place PS PP velocities Semblance Display Gather Display STCK Display CVS Display a oes input velocity Output velocity Semblance Single velocity function Database grid Browse Velocity domain Velocity type Time Depth f AMS C Interval 42 RadExPro seismic software www radexpro com Switch to the Semblance tab to set the main parameters of the semblance computation Set the velocity range from 1300 to 2500 m s with the velocity step of 5 m s and time step of 1 ms Additionally set the desired number of Constant Velocity Stacks CVS we will set this to 20 PS PP velocities Semblance Display Gather Display STCK Display CVS Display Super gather Input velocity Output velocity Semblance Use precomputed data Start velocity fa End vel
2. Get by ensemble con We will use in the FX domain that is the algorithm will be applied to the frequency spectrum of each individual trace Exponent 0 5 is equivalent of square root of the amplitude spectrum The module shall be places just before the Trace Editing Finally we will add Trace Output module to save the result as stack_final dataset The resulting flow shall look as following Help Options Database Tools Run Flow mode Exit Trace Input lt stack _migr Data l O Trgce in put lt sta ek d g h Trace Input Trace Output SEG Input SEG Y Output F K Amplitude Power SEG D Input RAMAC GPR Trace Editing Trace Output gt stack_ final ES 8 input JIOMC SEG Input G551 Input 5C5 3 Input Super Gather Load Text Trace Text Output Screen Display MB1 Drag module Ctrl MB1 Copy module MB1 DbIClick Module Parameters MB2 Toggle module Ctrl Ml 4 w 76 RadExPro seismic software www radexpro com Run it to save the processing result and see it on the screen Zoom Common parameters View Tools Exit Stop flow Exit a300 088 64G5S6 BO 1500 1600 1700 1800 1900 2000 2100 2200 The image looks a bit more sharp and focused than before If you have not yet closed the previous display of the same migrated stack without spectral whitening you may wish to zoom in to different parts of the records and compare them You may wish to compare the spectrums of the da
3. After you are happy with the settings and the preview close the Plotting Parameter dialog Like any other module the Plotting will not operate until you actually execute the flow Run the flow to start the printing job 82
4. File Velocity Field NMO Help gt N l 42 5 ois R x Iscop 0 ILINE 0 XLINE 0 Velocity m s Offset m CYS m s 1500 2000 43 4 1500 1750 2000 2250 q T 172 SCDP 0 ILINE 0 XLINE 0 I i iia gar g 1 I i 1 i t i i I sa J ti IE This is the very first super gather with not enough fold that is why the semblance at the left looks strange Use the drop down list in the top right of the window to switch to any super gather in the middle of the line where the fold is complete to estimate the quality of our parameters we will go to the SCDP 500 File Velocity Field NMO Help gt N 44 5 vie R x scop 500 ILINE 500 XLINE 0 Velocity m s Offset m CYS m s 2000 25 20 30 40 1500 1750 2000 2250 25 _ on i We can see that the semblance looks quite consistent with enough vertical resolution We might wish to decrease the gain here click the toolbar button to see the module parameter dialog and in the Gather display tab set screen gain Additional scalar to 0 6 The result is shown below 45 RadExPro seismic software www radexpro com Ce File Velocity Field NMO Help N gl Al a x Scop 500 mme so ame Velocity m s Offset m CVS m s 2000 25 20 30 40 1500 175 2000 Kal EALA UW WAU LTN We can see that the semblance calculation parameters we have c
5. Here is the result of velocity picking for this super gather ca File Velocity Field NMO Help gt N B elz foe x SCDP 100 ILINE 100 XLINE 0 1500 2000 25 10 1750 2000 2250 25 a ar he ER so Ths tt x mee STEEL Teint a v ZIEHE Cs Gk a he a a pa D ba te Bes Tel E EE Nee Co es To ee A ad ef aa a a i WEES a a T T E ET ER a ESE EE D A O TET a V 1874 T 185 SCDP 100 ILINE 100 XLINE 0 While picking you may wish to click the N button on the toolbar to apply real time NMO correction using the current velocity function to the super gather This is the way to see how your hyperbolas are flattened or not and adjust the velocity function when needed File Velocity Field NMO Help ejej N gl als x Velocity m s Offset m CYS m s 1500 2000 25 20 30 40 1750 2000 2250 25 _ m ott _ ote 196 SCDP 100 ILINE 100 XLINE 0 RadExPro seismic software www radexpro com When you are finished with picking velocities at this supergather go to another one In the drop down list the SCDPs with existing velocity functions are marked with File Velocity Field NMO Help gt In al elil R x Sepp 200 nme 200 nme SCDP 0 ILINE 0 XLINE 0 Velocity m s Offset m ILINE 100 XLINE 0 SCDP 200 ILINE 200 XLINE 0 25 20 30 40 ILINE 300 ILINE 400 ILINE 500 ILINE 600 ILINE 700 ILINE 800 ILINE 900 SCDP 10
6. Hote Ensembles will be defined by this number of sort helde Delete Add Delete f Selection te C Select from file File Database object Choose Cancel C Get all Then place the Trace Output module at the end of the flow and select the output dataset We will call it preproc preproc white Seasline S preproc Output sample format f A4 12 N UF Cancel And finally right click on the Screen Display in the flow to comment it when we run the flow this time we don t need to see the result The flow shall look like this Help Options Database Tools Run Flow mode Exit Trace Input lt raw Data I O Bandpass Filtering clang rapas en Amplitude Correction SEG input SEG Output SEG D Input RAMAC GPR SEG B Input IOMHC SEG 2 Input 655 Input 5C5 3 Input Super Gather MET Drag module Ctrl MB1 Copy module MET DbiClick Module Parameters MBZ Toggle modu 2 w Trace Output gt preproc screen Display Run it to preprocess the raw dataset and save the result as preproc dataset This may take few minutes 35 RadExPro seismic software www radexpro com NOTE If it takes too slow you may wish to terminate the flow by clicking on X button of the flow status window and change the flow execution mode to Framed using Flow mode menu before you run the flow In the Framed mode the flow reads only a frame of data of specified size at once which prevents the s
7. button and choose our sample ship positioning file ship_coords txt It content will be displayed inside the Edit navigation layout window For each of the fields in the list on the top left of the window one matching field and two coordinates specify its column in the file For that 1 select a field in the list 2 click on the corresponding column in the file contents and 3 click the Set column button to save your selection The selected column number will be displayed in the list After each field is assigned with its column specify the line range to be used In our file the first line contains the names of the columns and therefore shall be omitted Click on the second line of the file content and click the Lines From button to remember your selection You may keep the Line To as 0 this means that the module will try to read the file until the end Finally you Edit navigation layout dialog shall look like the following 12 RadExPro seismic software 1 2 2 39 Selection DATA ship_coords txt Click the OK button to save the layout Field switch off Set column A 18060 86666 1667 47421 1002 82843 1864 24264 1885 65685 1887 07187 1808 48528 1009 839949 1011 314371 1812 72792 1814 14214 y ckan sa000 5501 141421 5502 82843 5504 242664 5505 565685 55 7 07107 5568 48528 5569 89949 5511 31371 5512 72792 5514 14214 www radexpro com Coordinate system Lon Lat UTM Zon
8. DeGhosting Gas Hydrate Stability Zone Interpolation MEN Drag module Ctrl MEB1 Copy module MEI DbiClick Module Parameters MBZ Toggle module Ctrl MB2 oo v 14 RadExPro seismic software www radexpro com Click the Run menu command to execute the flow After the geometry assignment is complete you will see the following report window Geometry assigned to Can t assign geometry to Shots 1101 Shots 0 Traces 17616 Traces o Geometry Check Create a new flow and call it 030 geometry check The easiest way to check that the assigned geometry is correct is to 1 calculate theoretical first breaks of the direct wave basing on assigned offsets and the velocity in the water 1500 m s and 2 plot them on top of the seismic data in time scale to check if they match the observed direct wave or not That is what we are going to do in this flow Inside the flow we will add the following modules Trace Input to read the data from the project database Trace Header Math to calculate theoretical first break time for each trace and save it into a trace header field Bandpass Filtering to filter out the low frequency noise that disturbs data display Screen Display to view the data and plot the theoretical first breaks on top of it Add the Trace Input module into the flow We will read the data from our raw dataset where we just have assigned geometry to so add this dataset to the list of Data Sets W
9. Stop flow Exit ob Gee 6880802 BR Tr 685 Sam 0 Amp 0 ne N You may wish to zoom in and check that the pick is correct everywhere Now we need to move it a little bit upwards to have it just above the seafloor reflection we don t want to cut the wavelet with the muting and save the result 62 RadExPro seismic software www radexpro com Get back to the flow and add one more instance of the Trace Header Math place it after the Header Averager Here we will move our pick 1 3 ms upwards FEPICK FBPICK 1 3 Line 1 Pos 20 Cancel Check syntax Load templ Until now we have only been modifying FBPICK trace header values in the flow and observed the result on the screen without any output Now we need to save the result Of course we can add Trace Output module at the end of the flow to make a copy of the stack with the modified header however since the data itself was not modified here we would better save only the headers without creating an extra copy of the data This we can do using a module called Header lt gt Dataset Transfer Header transfer direction FROM dataset TO header it FROM header TO dataset Match by fields Assign fields FBPICK gt Here we will record header values from the flow back to the input dataset Select stack dataset where the header will be saved set CDP as the only matching field the dataset is the CDP stack and FBPICK as the o
10. Tools Run Flow mode Exit Super Gather Bandpass Filtering Amplitude Correction Screen Display Trace Input SEG Y Input SEG D Input SEG B Input SEG 2 Input SCS 3 Input Load Text Trace Data Input Geometr Headers MBT Drag module Ctrl MB1 Copy module MBI DblClick Module Parameters MBZ Toggle mod 2 w 39 RadExPro seismic software www radexpro com Run it to see how the coherency of the reflections was improved Zoom Common parameters View Tools Exit Stop flow Exit IEIEISTTTERSTT ISIS FIT Tr120 Sam 0 Amp 2 03 t0 0ms lt Now we can switch off the Screen Display we are happy with what we saw there and put a module called Interactive Velocity Analysis at the end of the flow The Interactive Velocity Analysis IVA can operate in 2 modes first it can operate as a conventional module in the flow with the Super Gather used for data input This mode of operation is convenient and intuitive however the disadvantage is that the IVA would be calculating semblance each time you switch from one super gather to another when the super gathers are big enough it can be time consuming and annoying Another way is to first use the Velocity Analysis Precompute module to pre compute all super gathers at once and then use the IVA as a stand alone module that takes the pre computed semblances as an input This makes navigation through super gathers much faster however ifthe pre compute was made with the
11. field Interval 100 0 r Font size fis Margins Lett axis 20 Too ayi u P axis Cancel margin m margin 120 mm Multiple Finally let us set up the first break plotting Click the Plot headers button in the Display parameters dialog and in the Header plot window that opens add FBPICK header where our calculated first breaks will be stored to the list of Curves to plot It the Curve parameters switch on the Time scale option and don t forget to switch on the Plot headers option in the General parameters otherwise no plots will be displayed The Header plot window shall look as shown below 18 RadExPro seismic software www radexpro com General parameters 7 Plot headers Fill backgorund Curve parameters Curves to plot Plot area position n Plot area width mm 1400 IM Whole range Min scale value Max scale value M Show scale Scale position Value marks onentation f Left Fight Applied static M Autoscale Current static Total static Marks distance Cancel The complete flow is shown here Help Options Database Tools Run Flow mode Exit Trace Input lt raw Trace Header Math Trace Input SEG Y Input SEG D Input SEG B Input SEG Input MB1 Drag module Ctrl MB1 Copy module MET DblClick Module Parameters MBZ Toggle mod 2 w Bandpass Filtering Screen Display Click Run to execute it you will see the following display 19 RadExPro seismic softwar
12. line 5 080 seafloor pick 17 10 04 Zoom Common parameters View Tools Exit Stop flow Exit Help f A 989 BAG 8aaB88 aa BAG Tr 300 Sam 967 Amp 3 29 t48 4ms LN There is still a couple of small rebounds in the middle of the line Ed OffshoreHiResMultiChan White Sea line 5 080 seafloor pick 17 43 03 Zoom Common parameters View Tools Exit Stop flow Exit A So O e 68GGee BOW Tr 899 Sam 2042 Amp 382 t 102 1ms lt 61 RadExPro seismic software www radexpro com We will fix them by alpha trimmed averaging of the pick values the algorithm first rejects a certain percentage of maximums and minimums and then averages the rest For the purposes of top muting this approach is good enough because the pick shall not be too precise Alternatively you may try to fix the rebounds by further increase of the threshold To apply alpha trimmed averaging the FBPICK values we add a module called Header Averager to the flow just after the First Break Picking Correct parameters are shown below Header Averager Trace Header FEPICK Honor ensemble windows length traces i boundaries Tipe Mode Running Average Normal Alpha Trimmed 50 C Subtraction Cancel Running the flow once again finally gives us the accurate seafloor pick ud OffshoreHiResMultiChan White Sea line 5 080 seafloor pick 17 53 17 a Zoom Common parameters View Tools Exit
13. lines Different fied Interval 100 0 m wv Multiple Font size fis Left axis T Run the flow to see the migration result Zoom Common parameters View Tools Exit Stop flow Exit 890 988 Sa 88 a8 BR 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 a a There are some slight migration artifacts above the seafloor we would mute the out using Trace Editing module with exactly the same parameters as in the 090 deghosting flow The result is shown below 74 RadExPro seismic software Ea OffshoreHiResMultiChan White Sea line 5 110 postprocessing 18 44 11 5 Zoom Common parameters View Tools Exit Stop flow Exit GQS6 Ga 688080 BR 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 Tr982 Sam 2453 Amp 431 t 122 7ms If you like to compare it with the unmigrated stack without closing the Screen Display go to the flow editor Copy the Trace Input in the flow with Ctrl Left Click comment one of the trace inputs and in the other one change the input dataset from stack_migr to stack_dgh Run the flow again to see the stack before migration Ed OffshoreHiResMultiChan White Sea line 5 110 postprocessing 18 44 53 Zoom Common parameters View Tools Exit Stop flow Exit op ae 68G6a00 BOW 100 200 300 400 500 600 700 800 900 1000 1100 1200 130
14. on the screen File Select View Zoom TPPELEE ELE GE PEPE PEE CED POPE EE EEP EP EEE EP CP PEPE EEE PEELE PEPE PEPE EPEC ECE EPEC EEC EPP EEE EEE EE PEEP EEE EE EUG EE EE EEE Eee 1700 1300 1900 2000 2100 HEEHEEEHENEUREEEREEHENEHHEEENERENNE 2200 2400 SOU_X IN 2042 819 5627 604 A 1000 1100 1200 1300 1400 1500 1600 For this training project we used artificial straight line coordinates so all our sources sit on the same straight line Our receivers and CDPs will sit on the same line as well In the real life with real coordinates the track plot will look more interesting Anyway now we will add receiver and CDP coordinates to the same cross plot Select View Extra headers menu entry and in the Extra headers dialog select REC_X and REC_Y for X and Y axes Set their point radius to 3 and click the Add button 23 RadExPro seismic software www radexpro com First header X axis Second header axis Point radius REC_X The same way add CDP_X and CDP_Y coordinates set their radius to 1 change color to green and Add this pair of headers to the list First header X axis Second header f axis Point radius gt Jer J mm Z ai X vs REC Y vs CDP Click the OK and see the result on the screen 24 RadExPro seismic software www radexpro com Hee x 3 SOU Y 2 MHHHEHEHEHEHEHUHLEHEHEHENEHEHHHHEHEHENEHHHEHHHHEHEHEHEHEHHHHHEHHEUEHEHEHEHEHEHEHHHHEHEHEHEHEHHEHHHENENEHEHEHHHHEHE
15. seismic software www radexpro com Enter the flow and add the Plotting module Dataset White Sealine 5 stack_final Select the stack_final dataset to be printed sorted by CDP Adjust printing gain Additional scalar the way you like here we set it to 0 2 Select a printer here we select the Microsoft XPS Document Writer included into Windows starting from XP SP2 that is a virtual printer that will generate an XPS document After a dataset and a printer were selected you may click the Layout Preview button to preview the printing result You can change any parameter and update the preview to see how it will affect the output 79 RadExPro seismic software www radexpro com Click the T Axis button to set up the vertical scale Tick length mm 2 0 Tick line width mm foz Tick length mm 1 5 Show values Scale Font Tick line width mm 0 1 Show grid lines I Show values Tick length mm a e Show grid lines Tick line width mm o a Hour HOUR Axis width 15 Minute MINUTE second SECOND Scale font Tite font f Linear axis Field I 3 Show values Tick length mm 3 CHAN Different 1 show grid lines Tick line width mm o a Time axis Hour HOUR es Minute MINUTE Multiple Axis width mm as Second SECOND Scale Fant Title font f Linear axis Ay Show values Tick length mm 3 Different show grid lines Tick line width mm o a f
16. the spectrum window now and click on the H toolbar button of the Screen Display and then on any trace on the screen You will see a Header Display window By default it shows all trace header fields associated to this trace The list of headers is long so the Header Display window is shown on the next page Scrolling through the list and clicking on different traces on the screed you may check which information is available in the trace headers rO seismic software www radexpro com RadExPro seismic software www radexpro com It may be not very convenient to examine such a long list of headers so you may wish to see only those header fields which you will really need to check and correctly assign positioning information FFID field record number shot number CHAN channel number SOU_X SOU_Y source coordinates REC_X REC_Y receiver coordinates OFFSET source to receiver offset CDP CDP number CDP_X CDP_Y CDP coordinates You may use View Select headers menu command to define the list of headers you want to see in the Header Display window and then View Show selected to actually display them The result is shown below Ad x u Zoom Common parameters View Tools Exit Stop flow Exit Help Soo Gee 6R8EGee2 808 Headers Display Tr 74 Sam 2638 Amp 28 t 131 9r lt As we can see from this much shorter and much more handy list we have correct shot numbers FFID and channel numbers CH
17. 0 1400 1500 1600 1700 1800 1900 2000 2100 2200 Tr1145 Sam 1371 Amp 0 Now you can switch between the 2 displays using the standard Windows Alt Tab command 75 RadExPro seismic software www radexpro com Finally we may wish to whiten the spectrum of the final stack to slightly improve the resolution and make the image better looking more focussed There are several modules that you can use for broadening and whitening of the data spectrum in RadExPro including Spectra Whitening Spectral Shaping and several types of deconvolution Here we will use on ofthe most simple means of spectral whitening one of the modes of the F K Amplitude Power module The F K Amplitude Power module raises either F K domain or F X domain amplitude spectrum to an arbitrary power and then performs the inverse Fourier transform 2D or 1D to the original T X domain Depending on the exponent value and the domain it is applied the result of the algorithm will vary from noise suppression to spectrum whitening generally spectral whitening is achieved with exponent values lt 1 while exponent values gt 1 make spectrum narrower suppressing the noise Choosing between F K and F X domain brings additional flexibility The most obvious way to whiten the spectrum using the F K Amplitude Power module is to rise the frequency spectrum of each trace to a power less than 1 Let us use it with the following parameters Exponent 0 5 IW FX domain only
18. 0 6500 7000 7500 8000 8500 9000 9500 f Hz f 9995 1Hz AffJ 03 Aabs f 1532 176 h We would apply a bandpass filter to slightly increase the singal to noise ratio and limit the spectrum this is important for the migration that we will do at the next step Insert the Bandpass Filtering 69 RadExPro seismic software www radexpro com module between the Predictive Deconvolution and Trace Editing with the following parameters Filter type Filter parameters Simple bandpass filter Low cut ramp 0 100 100 200 C Butterworth filter Notch filter High cut ramp 100 1500 Hz 0 S000 Hz Lancel Run the flow once again to check the result Zoom Common parameters View Tools Exit Stop flow Exit ao Dae 6e2G00e2 BUA File View Scale Parameters A a TR o o Tr f 9859 7Hz A f 022 Aabs f 1081 406 We may not necessarily see a big difference in the signal to noise level however we can see in the spectrum window that we have cutted high frequency noise oscillations and kept the useful frequency band nearly untouched 70 RadExPro seismic software www radexpro com Finally exit the Screen Display switch it off in the flow and add the Trace Output to save the result as stack_dgh The flow shall look as following Help Options Database Tools Run Flow mode Exit Trace Input lt stack Predictive Deconvolution Trace Input Trace Output SEG Y Input SEG Y Outpu
19. 00 ILINE 1000 XLINE SCDP 1100 ILINE 1100 XLINE CDP 1200 ILINE 1200 51 RadExPro seismic software www radexpro com Here is the result of velocity picking for the super gather 200 File Velocity Field NMO Help gt N ala fei 2 x SCDP 200 ILINE 200 XLINE 0 Yelocity m s Offset m CYS m s 1500 2000 25 20 30 40 1500 1750 2000 mS See ee ee Bee Te Sa ee ee ee Bug Ba O Ts O O D Te O O Ts O De O Ds Ts Ds Ts ss Be Be a Bu u Du Bu as Bu Tess Te Te Be Te Te ee Be De Ts Te Ds Ds Ts Ta Ts Be u _ _ E S E Fr _ ow lil _ Lu IN E Fr Fhe T E _ om EDEEEEEEEEBIENEEEEEEEEEEEENEEEEEEEEEEEEEEEEEEEEEEEEEEEETEEEEEEEEEEEEEEENEEEEEEEEEEEEEEEEEEEEEEEEEEEE EEE N fill _ En HIN Continue the same way until the end of the line If there is any supergather where you cannot pick velocities simply skip it The resulting velocity field will be interpolated and extrapolated for the whole line basing on the points where the velocity functrions were defined However be aware of the fact that it is the accuracy of the velocity picking that is crutial for the quality of the resulting stack When you exit the IVA module you will be prompted to save your velocity function Click YES to save the result WARNING velocity law was modified Would you like to save it before exit 52 RadExPro seismic softwar
20. 30 40 1500 1750 2000 2250 25 STR EEN NEN A eee A E E WARNAN NNN ee NEN NEEN RERNE NAE Peace e on a V 1501 T 95 ISCDP 0 ILINE 0 XLINE 0 Here you can see from left to right the semblance the super gather the dynamic stack consisting of one stack trace for each CDP gather of the current super gather and a set of constant velocity stacks 48 RadExPro seismic software www radexpro com You may wish to zoom in the useful time range along the vertical axis gt N elz R x scop 100 ILINE 100 XLINE 0 a SER 25 20 30 40 1500 1750 2000 2250 ET BRETT NENEN Ree A N Sr rr a F PEE EEEE AE n E a AARE Peaga R AA s lr n 11 1 Velocity m s Offset m CYS mis 1500 2000 25 20 30 40 500 1750 2000 2250 SINE oe es a oy ee bee bo eee Es Ee cad oe tos pes OM ot Be TT Be co pal ol St od Jer Re Os We et Re to pata Et pa penne 1 500 is Sra Tat pa Jat ee fel LS a ee fed Be ok fed Bt a 2 al ii TEE E ii i amp metenee gt 8 8 8 8 I ARAARA RANEA eee eee 95 SCDP 100 ILINE 100 XLINE 0 RadExPro seismic software www radexpro com Start picking velocities on the semblance panel you will see the corresponding hyperbola on the super gather panel and the cursor at the corresponding position on the constant velocity stacks panel You may decide sometimes to increase the semblance display gain to better resolves weaker maximums
21. AN read from the input file however no coordinates or offsets are available The CDP field seems to contain some nonsense arbitrary values which we will overwrite We will use FFIDs and CHANs to assign positioning information geometry to the data on the next step RadExPro seismic software www radexpro com Close the Screen Display now as we are ready to follow to the next step There is one last thing we recommend that you do here before exiting the flow right click on the Trace Output module in the flow to comment it When the module is commented its name is typed in italic it remembers its position in the flow and parameters but when the flow is executed next time the module will be skipped This would ensure that we do not overwrite our raw dataset occasionally after we assign geometry to it at the next stage Help Options Database Tools Run Flow mode Exit 5EG Y Input lt lineSraw sgy Trace Output gt raw Trace Input Trace Output Screen Display SEG Y Input SEG Y Output SEG D Input RAMAC GPR SEG B Input HOHE SEG 2 Input 655 Input 5C5 3 Input Super Gather MEI Drag module Ctrl MB1 Copy module MEI DblClick Module Parameters MBZ Toggle module Ctrl MBe w Geometry Assignment Create a new flow and call it O20 geometry assignment MB1 DblClick Default action MB2 Context menu MB1 Drag flow to lin FAR Enter the flow and in the list of modules on the right find a module called Marine Geomet
22. ANA HL factor Gain TEE Hone e I e a Humber of traces 100 MT Scale 10 r Wi f Entire screen Bias Tu Individual Rotate None Show every MW Ensemble boundaries M th trace l Variable spacing field Variable density display mode Normalizing factor Space to maximum ensemble width Grey None Ensembles gap E CAE Entire screen Custom Define w 0 Muliple panels E C None M Use excursion 2 0 traces Data velocity Display data 5 Palette range C Display velocity Set velocity l AHIS Show headers Min vel m s 500 0 Plot headers Header mark Max vel me 1500 0 Fickspolygons settings Save Template Load Template E Cancel This time we want to see FFID values along the horizontal scale Click the Axis button in the Display parameters dialog to set the scale parameters Set one of the two Traces scale fields to FFID set the radio button to the right to Different this means that the module will put a label on the horizontal scale with an FFID value whenever the value changes Make sure that the appropriate Values tick box is on otherwise the values will not display You may also like to label the time axis set Primary lines dt to 100 ms and switch the appropriate tick box on The Axis Parameters dialog shall look as following Different di Values PAID C Interval 00 mi Primary lines Multiple Secondary lines Different
23. HEHEHHHHHHHHEHEHEHEHHHHHHHEHHHHEHEHEHEHEHEHHRUNN 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500 SOU X X Y 1966 737 7082 000 i a As we expected sources receivers and CDPs all sit on the same straight line Using left mouse button select a small area to zoom in at the beginning of the line which is the left bottom corner of the cross plot x ing N PUP UP CEP EP UEC E PEC PEPE C PEPE EPEC EP CECE PEEP PEED EEC EP ECP PEEP PEE PEEP ECE PPE PEEP PEPE PEPE PE PEE CEP ECD PEEP EEE PEPE PEPE EP EEE EEE EEE ep eee 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500 SOU_X XY 1025 673 5451 725 ze A 25 RadExPro seismic software www radexpro com Now we can see our track in details it looks exactly as one would expected with the streamer orange being behind the source blue and the CDP locations at and in between of the source and receiver locations File Select View Zoom 970 975 960 965 990 995 1000 1005 1010 1015 1020 1025 X 990 967 5546 207 Close the cross plot and the CrossPlot Manager When closing the Manager window you will be prompted if you want to save your cross plots You may wish to save them to see the same windows again when you re run the flow Viewing Geometry Information in Geometry Spreadsheet Before we can go further with the processing we want to check the range of CDPs available we will need to have an idea
24. Interval Multiple a 35 Scale font Tithe Font Time axis 80 RadExPro seismic software www radexpro com Click the General layout button Here you can set up extra margins label and a logo M Left side Right side DECO Geophysical Software Company Label font High Resolution Offshore Data Processing Tutorial Text block width White Sea SEG Y Input line Sraw sqy Geometry Assignement BPF 75 150 2500 5000 Spherical Divergence Correction IVA MNMO correchon Y Constrain proportions Logo Position Left Right We select to display the label on the left side of the image and manually fill in the label fields company name project title project location and comments In the comments we have manually typed the processing history of the section to be printed you can do the same if you like unfortunately for the moment there is no way to place the history there automatically Finally we have added our logo from a BMP file that is located in the DATA folder of the demo project You can use your logo instead or any nice picture in the BMP format 81 RadExPro seismic software www radexpro com After you finish with the settings click the Layout Preview button to see the preview of the print out U x File View xX Qa SOC Liar company If you unzoom you can see the whole document separated into pages by dashed lines Here we are going to have 2 landscape oriented A4 pages
25. RadExPro seismic software radexpro com You flow shall look like this OffshoreHiResMultiChan White Sea line 5 070 stacking Help Options Database Tools Run Flow mode Ext Trace Input Trace Output SEG Y Input SEG Y Output SEG D Input RAMAC GPR SEG B Input HOHE SEG 2 Input GSSI Input 5C5 3 Input Super Gather MB1 Drag module Ctrl MB1 Copy module MB1 DblClick Module Parameters MBZ Togi 2 w Run it and see the result on the screen Ea OffshoreHiResMultiChan White Sea line 5 070 stacking 18 01 20 5 Finan Common parameters View Tools Exit Stop flow Ext Help P a bs aaa 66868 geo 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 t 0 0ms Tr1054 Sam 0 Amp 0 This is our stack What we can see here is a complex structure with a lot of diffraction hyperbolas migration will definitely be a need for this data Another problem we can see is a pretty wide wavelet with a prominent ghost wave 56 bd OffshoreHiResMultiChan White Sea line 5 070 stacking 18 01 20 SES Zoom Common View Tools Exit EEE flow T Help G A San BEG m CDP 1200 1300 1400 1500 1600 om a ae Kern ra nah ht nn en BR 13 Tr 1635 Sam 2566 Amp 4 88e 003 t 128 3ms EM lt gt afloor Pick for Top Mutins C JC i Before we continue further with the processing let us prepa
26. RadExPro seismic software www radexpro com Offshore High Resolution Multichannel Seismic Data Processing in RadExPro Software Rev 05 12 2013 Working with this tutorial you will need to use OffMCData zip containing 2 files line5raw sgy is a data sample in SEG Y format This is a boomer line from the White Sea acquired with 16 channel streamer Channel spacing was 2 m offset from the source to the first channel 14 m ship_coords txt contains sample ship positioning information in ASCII format The file contains 3 columns shot point number FFID X coordinate of the ship and Y coordinate of the ship It looks as following FFID X Y 1400 1000 00000 5500 00000 1401 1001 41421 5501 41421 1402 1002 82843 5502 82843 It is assumed that before working with this tutorial you have already got some basic theoretical knowledge of multichannel data processing For the details of individual modules mentioned here please refer the latest version of the RadExPro User Manual available at www radexpro com Please note that seismic processing is to a large extent data dependent so this tutorial cannot cover all possible cases or issues you can find in your data What is described below is just a typical processing workflow that can be taken as a basic guideline for the real life data processing In case of any questions please contact us at support radexpro ru Data Input and Visual Check First create a new project and load the in
27. Screen Display and insert Predictive Deconvolution module above the Trace Editing Set the Prediction Gap to 1 5 ms according the estimated ghost wave delay and increase White Noise Level to 0 1 to make the result less noisy Start Time i End Time fo Frediction Gap 1 Deconvolution Operator Length 50 White Noise Level 1 Cancel Run the flow The result is shown below 68 RadExPro seismic software fd OffshoreHiResMultiChan White Sea line 5 090 deghosting 18 07 55 oth Zoom Common parameters View Tools Exit Stop flow Exit Help A Tr 600 Sam 1376 Amp 0 t 68 8ms A As you can see the ghost has been efficiently suppressed and the resulting wavelet became narrower however the result is a bit noisier than the original record If you take the spectrum of any useful part of the record it would look similar to what is shown below LJ OffshoreHiResMultiChan White Sea line 5 090 deghosting 16 55 42 Zoom Common parameters View Tools Exit Stop flow Exit Help a E gt Ge Im Ga a z EJ Aes LH er Spectrum 5 File View Scale Parameters A 100 502 ie UNE BSNINIBINISEINIRISINIBCRSINISUNIEINISIEINISISINININIENIRININIDINIRISUNISISIRISISISSOSUAISISININININISUNISLSINIESIAIAISINISINININISLAISISIAISGURINISISISIAISISIAISISUAISIGRISISIRINIAIAIRISIAIEIAIA 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 600
28. ace Input lt stack Trace Editing Screen Display MB1 Drag module Ctrl MB1 Copy module MB1 DbiClick Module Parameters MEZ T w Run it to see the muting result Zoom Common parameters Vi Tools Exit Stop flow Exit 996 666 666666 688 Tr 1440 Sam 1224 Amp 0 t 61 2ms You can move the mouse cursor through the area above the seafloor to make sure that the amplitudes there are all O the amplitude at the cursor position is displayed in the status bar 66 RadExPro seismic software www radexpro com We need to estimate the delay between the primaries and the ghost waves Zoom in somewhere to the seafloor reflection Zoom Common parameters View Tools Exit Stop flow Exit 890 Ge 6866Ge BBA Tr 1328 am 2174 Amp 0 t 108 7ms lt Click the oO button of the toolbar and set vertical scale primary lines to 1 ms C Different di Values feld Interwal 100 Mm Primary lines f1 intial Secondary lines Different field Interval 100 0 m Font size E Margins Left axis To AE on paris Cancel magn 20 mm agn 2D mm Multiple 67 RadExPro seismic software www radexpro com Now you can see that the gap between the primary seafloor reflection and the ghost wave is about 1 5 ms Zoom Common parameters View Tools Exit Stop flow Exit oo O e BaB8daoa BL Tr 1342 am 2175 Amp 0 t 108 8ms lt We can try this value as a prediction gap in the deconvolution Close the
29. ange aperture tapering m 50 Output Dataset White Sealline S etack_migr Select our deghosted stack stack_dgh as the input dataset We will take the migration velocities from the project database select the v1 velocity function that we created in the Interactive Velocity Analysis module The X step is the spatial increment between traces it shall be equal to our CDP spacing bin size that is 1m Set the Max freq to migrate to 3500 Hz This will guarantee that all useful frequencies high cut at 3000 Hz are included into the migration One of the most important migration parameters is the range aperture There is a general rule of thumb that migration aperture shall be taken at least as big as 0 6 of the maximum expected depth of interest Here the seafloor is at around 100 ms which is 75 m and the overall record length is 200 ms with the RMS velocities increasing from 1500 m s at the seafloor to around 2000 m s This would give us a reasonable estimate of the maximum depth as around 150 m so the aperture shall be at least 90 m We would set it to 100 m to be on the safe side Range aperture tapering shall be small relative to the aperture Set it to 5 m The output dataset we will call stack_migr 72 RadExPro seismic software www radexpro com Run the flow Help Options Database Tools Run Flow mode Kirchhotf Migration Trace Input SEG Input SEG D Input MET Drag module Ctrl MB1 Copy mod
30. ated at the previous step and click the Ok button 10 RadExPro seismic software www radexpro com Object name raw Objects Location E White Sea line 5 O10 data input oo O20 geometry assignemnent Rename Delete Now we need to select how our ship navigation will be matched to the dataset traces There are two options available Time match and Header field match Since our sample file with ship positioning contains coordinates for each shot number select the Header field match option In the enabled Select header drop down box select FFID header field In Time match mode the following headers Select date 07 1 1 2013 must be filled YEAR DAY HOUR MINUTE SECOND Otherwise matching could not be Julian day fan performed Use interpolated coordinates for Header DAY must contain Julian day traces with same time stamps Header field match The date specified conesponds to the first ine of a navigation file Select header FFID 11 RadExPro seismic software www radexpro com Click the Ship navigation button to select a navigation file and specify its layout The Edit navigation layout window will open Definition of Field i an peace Mathching_field 1 on Ship GPS UTM X 4 UTM Zone number PT Ship GPS UTM Y 5 ere Field switch off he value of switched off field wil be padded by zero Set column Load template Save template At the bottom right click the Select file
31. creen Display window you see several raw shots displayed one after another One can clearly see the direct wave marked on the figure by blue arrow seafloor reflection marked by orange arrow and some subbottom reflections below it Another thing one can notice here is the strong low frequency noise interfering with the data Click at the spectrum button on the toolbar and then use left mouse button to select a rectangular area on the screen to calculate the average spectrum A new window with the average amplitude spectrum of the selected data fragment will open and the rectangular area will be marked by a frame RadExPro seismic software www radexpro com Ag Zoom Common parameters View Tools Exit Stop flow 3095 008 60050000D Spectrum 5 File View Scale Parameters A 100 p ie i i ul Hi lik Im Hl 11 zz waded iit 1000 2000 3000 4000 5000 6000 7000 38000 9000 f Hz IE wall i ren w ail un os Tr70 Sam 0 Amp 120 t 0 0ms lt f 988 1Hz Af 17 Now you can clearly see this strong low frequency noise below the 100 Hz This is quite typical for the high resolution offshore seismic data recorded without a low cut analogue filter This noise is believed to be related to the ship operation RadExPro seismic software www radexpro com File View Scale Parameters 200 300 400 500 600 700 g0 900 T Hz f 329 8 Hz Aff 9 Aabs f 14880 078 Close
32. der Math First Breaks Picking Screen Display Trace Input SEG Input SEG D Input SEG B Input SEG 2 Input MB1 Drag module Ctrl MB1 Copy module MET DbiClick Module Parameters MEZ Toggl 2 w The last thing before we run the flow let s setup header plot in the Screen Display to see the detected seafloor on top of the data In the Screen Display parameters click the Plot headers button and select 59 RadExPro seismic software FBPICK to be plotted in time scale General parameters Plot headers Fill backgorund Curve parameters Curves to plot W Time scale Color Plot area position fo Plot area width mm 100 IY whole range Min scale value fo Max scale value fo M Show scale Scale position Value marks onentation f Left t Fight IY Autoscale Marks distance f T Cancel Run the flow The result is shown below Zoom Common parameters View Tools Exit Stop flow Remove I Current static Applied static Total static www radexpro com dab 668 688606 888 Tr 1559 Sam 1066 Amp 149 t 53 3ms 60 RadExPro seismic software As you can see the seafloor detection was almost ok but in some places it failed reaching the threshold too early Close Screed Display open First Break Picking parameters increase the threshold up to 2000 and run the flow once again The result looks much better fd OffshoreHiResMultiChan White Sea
33. der was filled in by Marine Geometry Input module it is defined in meters Sound velocity in water is 1 5 km s m ms so the resulting values will be in ms Header field names in the right part of the equation shall always be in square brackets The module dialog shall look as following 16 RadExPro seismic software www radexpro com FBPICK OFFSET 1 5 Load template Save template Add Bandpass Filtering module with the following parameters Filter type Filter parameter Simple bandpass filter Low cut ramp 0 50 Hz Ormsby bandpass filter 100 100 Hz PICOEE COO UCC OU SDOoo a e a a e a a a C Eutterworth filter Notch filter High cut ramp 100 5000 Hz 02 10000 Hz Lancel This would filter out most of the low frequency noise while the high frequency part of the signal will not get affected we remember that the useful frequencies end at about 2500 Hz Add Screen Display at the end of the flow This time we will change some parameters First we will switch on the Ensemble boundaries option to see the data divided by ensembles Ensembles in RadExPro are defined in the Trace Input module by a specified number of first sorting keys In our case number of ensemble keys is set to 1 while the first sorting key is FFID This makes shot gathers to become the ensembles 17 RadExPro seismic software www radexpro com WoT MA display mode Teer Framt 10 0 to o o Boorse fio OW L
34. des at the seafloor are of the order of 10 while those above the seafloor are typically less than 1000 This give us a clue about the threshold we can use for the seafloor detection let us try up with 1000 and see how it works Note if you have used different processing the amplitudes will be different Check them yourself before using the numbers we recommend Ok now we know everything we need to make a flow for automatic seafloor detection Close Screen Display and add First Break Picking module to the flow Set the following parameters First Break time header word FEPICE r First Break amplitude header word PREAMP Horizon header word PICK1 Window length an Treshold C Derevative Treshold kon Set clean m calculate dereyalive Min Type Max O Replace trace with derivative Sign Change Treshold Cancel Here Horizon header word is the trace header from where it will read the start horizon values We select PICK1 header here but until now it is empty Before we can run the flow we need to write the value 80 there and we need to do it before the First Break Picking 58 RadExPro seismic software www radexpro com So we will add Trace Header Math module to the flow between the Trace Input and the First Break Picking and will fill PICK1 header with 80 The flow shall look like this Help Options Database Tools Run Flow mode Trace Input lt stack Trace Hea
35. e OffshoreHiResMultiChan White Sea line 5 030 geometry check 16 17 27 a Zoom Common parameters View Tools Exit Stop flow Exit GQ6 GABE 6GSG6ee BUe Tr89 Sam 4099 Amp 2 01 205 0ms AM lt gt T The yellow line here is the theoretically calculated direct wave arrival time curve Click Zoom n amp toolbar button and select an area with the direct wave for a blow up You can clearly see that the EeYNrN CAM p AN ULV 1 l theoretical direct wave arrival time based on the geometry fits nicely to the observed direct wave which means that the assigned geometry is correct Zoom Common parameters View Tools Exit Stop flow Exit ANECON i ie OffshoreHiResMultiChan White Sea line 5 030 geometry check 16 17 27 5 FFID 1400 1420 1440 1460 1480 1500 Sam 0 Amp 35 6 t 0 0ms RadExPro seismic software www radexpro com Viewing the Track Line in CrossPlots module Sometime you may wish to have a look at your track line viewing simultaneously the source receiver and CDP locations This is another way to check your geometry In RadExPro this can be done using the CrossPlot module Similarly to the Marine Geometry Input this is a stand alone module so we will create a new flow for it and call it 040 positioning cross plots MEI DblClick Default action MBZ Context menu MB Drag flow to line to copy w E
36. e number ee UTM_X UTM_Y e value of switched off field wil be padded by zero Load template Save template Now go to the Source streamer geometry tab of the module parameter dialog to specify the acquisition system geometry Select the parameters of the acquisition system as shown on the figure below 13 RadExPro seismic software www radexpro com Ship navigation Source streamer geometry STREAMER Positive X Positive y SOURCE When you click on a geometry parameter here it will be high lighted on the scheme We specify that our 16 channel streamer with 2 m channel spacing was towed 20 m behind the ship GPS antenna The source was towed 6 m behind the antenna which gives us 14 m offset of the nearest channel Both the source and the streamer were towed on the same line with the GPS antenna otherwise we would like to define their side offsets indicated as dx as well Finally we indicate the desired bin size normally it is selected as half the receiver spacing which in our case is 1 m For 16 channel streamer this would result in 8 fold CDP gathers Click the OK to complete the parameter settings Your flow shall look as following Help Options Database Tools Run Flow mode Exit Marine Geomeiry ipui Data Manipulation a Data Filter Comments Auto Picking First Breaks Picking Marine Marine Geometry Input Tides Import Dropped Missed Shots Correcti Swell Filter Zero Offset DeMultiple
37. e want to have our data sorted first by shot number FFID and the within each shot gather by channel number CHAN so select FFID and CHAN as Sort Fields After you add 2 sort fields the Selection edit string will be set to indicating that for both sorting keys we are going to read the whole range of data all FFIDs and all CHANs However we want just to check our geometry here so we probably don t need to read all shots every say 20 shot would be enough So change the selection sting and make it as following 15 RadExPro seismic software www radexpro com 0 100000 20 This selection mask indicates that the module will read every 20 shots FFIDs within the whole available range literally from O to some very big number that definitely exceeds the maximum FFID value in the data And within each shot all channels will be input into the flow Finally the module parameter dialog shall look as following sort Fields FFIO Number of Ensemble Fields i Hote Ensembles will be defined by this number of sart fields Delete Add Delete f Selection C Select from file File C Database object Choose Cancel C Get all Add the Trace Header Math this module is a built in formula editor for trace headers We are going to calculate theoretical first breaks here and save the values to a header called FBPICK For that we will use the following formula FBPICK OFFSET 1 5 OFFSET trace hea
38. e www radexpro com Stacking Now when we have velocities available we can apply NMO corrections to the data and make a CDP stack Create a new flow for that 070 stacking Help Options Database Tools Exit MB1 DblClick Default action MB2 Context menu MB1 Drag flow to line to copy FAR Number of Ensemble Fields fi Hote Ensembles will be defined by this number of art feld Delete f Selection aaa Select from file File Database object Choose OK Cancel C Get all 53 RadExPro seismic software www radexpro com Then we will add NMO NMI module to apply the NMO correction On the Velocity tab select the v1 velocity we have created at the previous step NMO Velocity Single velocity function 50 1000 2 5 2000 2 7 3000 2 9 Browse l 0 Database picks I Ar Database grid Browse Velocity domain Velocity type Time Depth RMS Interval Save template Load template OK Cancel On the NMO tab you may wish to set Mute percent to 30 This is the stretch muting parameter parts of the traces that stretched by NMO correction for more than 30 will be muted out This would allow us to mute the direct wave out although at this data it is probably not that important the direct wave here is not interfering with the reflection anyway NMO Velocity f NMO Mute percent 30 NMI Use coordinate interpolation Save t
39. ed by FFID OFFSET Get all C Selection 30 Survey 2D Survey Profile ID f Remap header value RECHO 41 1817 SOURCE 4 1857 ILINE_MO 41 1837 ALINE Add Delete Load ist Save ist Load remap Save remap on File raw White Sealine BAraw Output sample format f A4 2 N Cancel WoT AWA display mode Fromt 0 0 ta 10 0 Bl Sweetie io OWA Normalizing factor Gain es f None C wT A Eey R Number of traces foo MT Scale fo om vA Entire screen Bias fo Individual Rotate None a OW every Ensemble boundaries H th trace Variable spacing field Varable density display mode Tee rena Space to masimum ensemble width 5 Grey C None aan 03 FB oe E bles E Entire screen Bias are eae Custom Define eue Muliple panels lo None Te lise excursion 20 Panes Data yvelocity Display data Display velocity Set velocity Palette anna AMIS Show headers Min vel ms 500 0 Plot headers Header mark Max vel ms 11500 0 Pickspolygons settings Save Template Load Template E Cancel RadExPro seismic software www radexpro com Execute the flow using Run menu command The data will be read from the file saved to the project database and then displayed on the screen Ad x Zoom Common parameters View Tools Exit Stop flow Exit Help SoaD8BB 688002808 f Tr 42 Sam 0 Amp 83 t 0 0ms lt In the S
40. emplate Load template Cancel After the data is corrected for the NMO it can be stacked using Ensemble Stack module Add it to the flow The Ensemble Stack module stacks all traces of each ensemble into one trace The ensemble is defined in the Trace Input at the beginning of the flow Since the Number of Ensemble Field there is set to 1 and 54 RadExPro seismic software www radexpro com the first Sort Field is set to CDP our ensembles will be CDP gathers and the result of stacking will be a CDP stack In the module parameters we would recommend that you set the Mode of stacking to Alpha trimmed with 30 rejection percentage This would reject 30 of maximum and minimum amplitudes of each sample before stacking of the remaining values In most cases this mode brings a clearer less noisy stack although takes a little bit more computation time Mode C Mean Median Alpha trimmed 30 A fao Window traces E Filter length ms 60 C Coherent stack M Treat zero as result of muting Cancel stack White SeaSline Shstack Output sample format f A4 12 N UF Cancel Finally add a Screen Display to see the result one the screen Set Number of traces as 2300 to see all traces on the screen at once You may also wish to adjust scales to have horizontal lines marking every 50 ms of TWTT along the vertical scale and having every CDP labeled along the horizontal scale 55
41. er gather Add Screen Display at the end of the flow so we can check how our super gathers look like Switch on the ensemble boundaries option and set horizontal scale to 300 traces per screen WoT AMA display mode Fromt 00 bo o o t Scale 0 CWT vA Bees ised Gain 03 Hone ic WT m 1 Humber of traces 300 NM Scale 10 nun 5 a Bias Tu ndividua Rotate None Show every i W Ensemble boundaries th trace Variable spacing field Variable density display mode Normalizing Factor Space to maximum ensemble width Grey None Ensembles gap E RB Entire screen Custom Define Indiens Muliple panels E C None M Use excursion 2 0 traces Data velocity Display data l l l Falette range C Display velocity Set velocity l ot ae Show headers Min vel m s 500 0 Plot headers Header mark blas vel mis 1500 0 Fickspolygons settings Save Template Load Template E Cancel 37 RadExPro seismic software The result of the flow execution is shown below E OffshoreHiResMultiChan White Sea line 5 060 velocity analysis 17 37 03 5 Zoom Common parameters View Tools Exit Stop flow Exit Help op Dae 688060 BR i LOH SESS Tr46 Sam 0 Amp 0 643 t 0 0ms EN lt gt We can see that some super gathers look disturbed this is because of abruptly changing bathymetry However even those disturbed supergat
42. ew Tools Exit Stop flow 300 G68 Bassas ann N Tr 46 Sam 3952 Amp 35 3 t 197 6ms lt You may wish to try different parameters of the filter and run the flow several times comparing the results and selecting the one you like most If you have several Screen Displays open you can always use the View History menu command to view the very flow that resulted in this particular instance of the Screen Display DP TITTY ET You can double click on any module in the Flow History and see its parameters 32 RadExPro seismic software www radexpro com OffshoreHiResMultiChan White Sea line 5 050 preprocessing 16 55 55 Zoom Common parameters View Tools Exit Stop flow Exit aD Gee BB 88a0 BL 1 Trace Input lt raw Bandpass Filtering Screen Display u r Filter type Filter parameters Simple bandpass filter Low cutramp 0 75 Hz gessnssnnsnnsensnnnsnnsnnsnnnnn nennen snn nennen Ormsby bandpass filter 100 1150 Hz Butterworth filter Notch filter High cut ramp 100 2500 Hz 0 5000 Hz Cancel Tr 70 Sam 784 Tr70 Sam 784 Amp 15 8 t392ms 03 t 39 2ms EN lt gt Now we shall compensate amplitude attenuation due to spherical divergence We will use the Amplitude Correction module for that with the following parameters Action to n Exponential correction dB me E Automatic gain cont
43. hers demonstrate rather consistent reflection hyperbolas Before we can start velocity analysis we need to additionally prepare the data Generally the only thing we are interested here is the coherency of the reflections whatever will be the wavelet and the resolution So before we run velocity analysis we would make some strong additional processing that will be used only here it will not propagate to the stack We will add a narrow band frequency filtering and a narrow window Automatic Gain Control AGC to improve the reflection coherency For the filtering here we will use Bandpass Filtering with the following parameters Bandpass filtering Filter type Filter parameter Simple bandpass filter Low cutramp Use 150 100 300 c wa filter Notch filter High cut ramp 100 700 Hz Os 1000 Hz Lancel 38 RadExPro seismic software www radexpro com It will follow with the Amplitude Correction where we make the AGC with 10 ms operator Acton to apply Spherical divergence correction n Operator length mg Type of AGC scalar Basis for scalar application fio MEAN CENTERED Automatic gain control Trace equalization Basis for scaling Time gate start time m Time gate end time rms MEAN lo E I Time variant scaling Specify amplifying law along trace t me Example format H ik1 2 ta kz Ik Cancel The flow shall look now as it is shown below Help Options Database
44. hosen are reasonable so now we can exit the IVA module pre compute semblances with the same parameters and then run the IVA once again in the stand alone mode For that add Velocity Analysis Precompute module to the flow and set its parameters as shown below Semblance Start velodty m s 3 End velocity m s Velocity step m s Time step ms Mute percent Constant Velocity Stacks Number of CVS stacks Bin offsets Start offset Offset step VA Precompute result White Sealine S semblance_precomputed We will save the precompute result as a database object called semblance_precomputed 46 RadExPro seismic software www radexpro com Now comment the Interactive Velocity Analysis and run your flow it shall look as shown below Help Options Database Tools Run Flow mode Exit Super Gather Bandpass Filtering Amplitude Correction Trace Input SEG Y Input SEG D Input SEG B Input SEG 2 Input SC S 3 Input Screen Display interactive Velocity Analysis Velocity Analysis Precompute MB1 Drag module Ctrl MB1 Copy module MEI DblClick Module Parameters MB2 Toggle module Ctrl MB2 DBICI 2 w The pre compute will take few minutes After it is complete uncomment the Interactive Velocity Analysis module and comment all other modules in the flow now the IVA is going to operate as a stand alone module Double click on the module name to open its parameter dialog and on the Semblance tab switch on the Use
45. lowing headers in the list FFID CHAN SOU_X SOU_Y REC_X REC_Y OFFSET CDP_X CDP_Y CDP After you click the OK the Geometry Spreadsheet shall look as following Fields Edit Tools Exit maemo mm cman sous souy mcx mcy ons cox coy m MET oo srs sosar meseme sussene 1000 soar sum 1 ae ood srne swszsme osease sisses 1600000 soams sooroo 1 ar ood mens swszeme osnon sasos 1800000 sans sinn 1 as oo msrme osre muss sarasa 2000000 sesame sum 1 ae 00s S erne eose seoanini sunan on 2200000 serarsis errors 1 ae mo 1 De osre swereme orase s ramuss 2400000 seraras sarao u as eo 1 7 sre swerene ornes sanss 2000000 ses swesser m en ie e ee 547595837 28 00000 osssers6 sus gt aes ee ee ee 5495 78736 en sus sosse ee mens nam 2 _ a um u Double click on the CDP column to have the lines sorted according to the CDP numbers You will see that the starting CDP is 1 Scroll down until the end of the window to see the last CDP it is 2216 28 RadExPro seismic software www radexpro com Fields Edit Tools Exit a a a nn en ce er oe me m 13T eases nase amea mann ioo T zen gt em oe 2 Taten noran once f eea oa se nee m am oe 7 gt ern nen V aeram Tram nme S aan 8 ij HH ZI IE IE IE E I IE IE IE 528153 212 E sla lais lelea l2 s 3 13 lslsl
46. m Rotate Nore ndividua Ensemble boundaries 7 jra 1 Variable spacing field Variable density display mode Normalizing factor Space to mazimum ensemble width Grey C None Ensembles gap 2 AE Entire screen C Custom Define Individual Muliple panels E C None een 20 Feces Datavelocity f Display data Palette range Display velocit Ass Show headers oe i Min vel m s 500 0 Flot headers Header mark Manwel ms 1500 0 Picks polygons settings Save Template Load Template ox Cancel 64 RadExPro seismic software www radexpro com Insert amodule called Trace Editing in between of this two this is the module where we will actually apply our top muting On the Trace Editing Parameters tab set Muting type as Top muting and Taper Trace Editing parameters Horizon Muting Top muting Bottom muting Muting in window Taper window length Save template Load template Cancel Then switch to the Hozion tab to specify the muting horizon window length of 1 ms Trace Editing parameters Horizon Pick in database Select f Trace header FBPICK Our pick was saved to the FBPICK header field so switch on the Trace header option and click the Browse button to select the FBPICK header there 65 RadExPro seismic software www radexpro com For the moment our flow looks as following Help Options Database Tools Run Flow mode Tr
47. nly assign field 63 RadExPro seismic software www radexpro com Switch off Screen Display we don t need it anymore The flow shall look like this Help Options Database Tools Run Flow mode Exit Trace Input lt stack Trace Header Math Trace Input Trace Output First Breaks Picking SEG Y Input SEG Y Output Header Averager SEG D Input RAMAC GPR Trace Header Math SEEI TANIN Srreen Display SEG 2 Input 655 Input Header lt gt Dataset Transfer gt stack Input Super Gather Load Text Trace Text Output Data Input Data Output MB1 Drag module Ctrl MB1 Copy module MB1 DblClick Module Parameters MB2 Toggle module Ctrl MB2 DblClick Delete Run it to detect the seafloor fix the rebounds move the pick above the seafloor reflection and save the result back to the input dataset De Ghosting Let us address the problem of long wavelet with a ghost wave Create a new flow 090 deghosting There are several methods that can be used to suppress the ghost wave in the software here we will use predictive deconvolution However before doing this we will try the top muting that we have prepared at the previous stage Create a flow with the Trace Input select stack dataset sorted by CDP and Screen Display set 2300 traces per screen From t 80 WoT AMA dieplay mode Fiom t 80 0 to 0 0 Te fio WTA Normalizing factor Gain TEE None Number of traces 2300 8 Scale fio z vA F en Bias mu T
48. nter the flow and add CrossPlots module if you start typing the name of the module while the cursor in within the list of modules you will see a list of those matching your typing otherwise you can find it in the QC group of modules You will see the parameter dialog select Get trace headers from dataset and select the same raw dataset with geometry Get trace headers from dataset Get trace headers from ASCII tile ie white Sealine Sravy u lc F Crossplot collection path m First Reference Header Second Reference Header TRACENO TRACEND Click the OK to save the parameters and then run the flow You will see the CrossPlot Manager window 21 RadExPro seismic software www radexpro com Click the New Crossplot button and select a pair of headers to be displayed as the main headers of the crossplot that would define the scales we will add additional pairs of headers to the same cross plot later Select SOU_X for X axis and SOU_Y for Y axis First header axis Second header t axis Sou_x f Number of Columns 100 Histogram Column Width 1 Point properties con Click the Point properties button and set Radius to 5 we want to have source locations thick enough to be hidden by receiver and CDP locations we are going to add later 22 RadExPro seismic software www radexpro com Click OK here and in the New CrossPlot dialog to finish the cross plot creation You will see it
49. ocity 25000 1 Save template Finally we will adjust the display parameters at the corresponding tabs Semblance display Super gather Input velocity Outputvelociy Semblance PS PP velocities Semblance Display Gather Display STCK Display CVS Display 43 RadExPro seismic software www radexpro com Super gather display Super gather Input velocity Output velocity Semblance PS PP velocities Semblance Display Gather Display STCK Display CVS Display Save template Load template OK Cancel Here click the Palette button to select or set manually a color pallet you like The pre defined palettes are stored inside the RadExPro program folder in the PALETTES subfolder We will use the black white orange palette from the blkwtord pal file We will use the same display parameters for the super gather Gather display dynamic stack STCK Display and constant velocity stacks CVS Display Now your flow shall look as following Help Options Database Tools Run Flow mode Super Gather Bandpass Filtering Amplitude Correction Screen Display Interactive Velocity Analysis Trace Input SEG Y Input SEG D Input SEG B Input SEG 2 Input Cee Banana et MB1 Drag module Ctrl MB1 Copy module MB1 DblClick Module Parameters MB2 Toggle module Ctrl MB2 Dbl 2 w 44 RadExPro seismic software www radexpro com Run it to see the Interactive Velocity Analysis window
50. of it on the next stage For that we will open the raw dataset in the built in spreadsheet tool called Geometry Spreadsheet This tool generally is used for control and editing of any trace header information 26 RadExPro seismic software www radexpro com Either from the flow editor window of from the main program window with the project tree call the Database Geometry spreadsheet menu item Help Options Database Tools Run Flow mode Add data file Geometry spreadsheet Database manager Dataset history DAF export MB1 Drag mod Edit header fields Database management In the open dialog select the raw dataset and click the OK Object name raw Objects Location E White Sea line 5 O10 data input l 020 geomet assignement 030 geometry check i O40 positioning cross plots gt Rename Delete History Cancel If you open the Geometry Spreadsheet for the first time you will see one default header column TRACENO otherwise it will remember the last set of headers you used 27 RadExPro seismic software www radexpro com Fields Edit Tools Exit TRACENO HE Select Fields Add field menu to select those headers you want to see from the list you can use Ctrl and Shift keys for multiselect Our main interest here is the CDP range however you may wish to open the complete set of important headers related to the line geometry to check them once again Select the fol
51. ow looks as following Help Options Database Tools Run Flow mode Exit Trace Input lt raw Screen Display Trace Input SEG Y Input SEG D Input SEG B Input SEG 2 Input SCS 3 Input MB1 Drag module Ctrl MB1 Copy module MB1 DblClick Module Parameters MB2 Toggle mod 4 w Run it to see the raw CDP gathers Zoom Common parameters View Tools Exit Stop flow 305 008 030000 ep0 Tr54 Sam 0 Amp 74 t0 0ms lt We need to add bandpass filtering to the flow to filter out the low frequency noise You may wish to look at the data spectrum here once again to get more accurate parameters 30 RadExPro seismic software www radexpro com We will use the following parameters of the filter Filter type Filter parameters Simple bandpass filter Low cut ramp 0 75 Hz Ormesby bandpass filter 100 150 Hz PATOEE COO CI IO OBSDOooDoC E a ea e E a C Eutterworth filter Notch filter High cut ramp 100 2500 Hz Oe 5000 Hz Lancel The flow now shall look as following Help Options Database Tools Run Flow mode Exit Trace Input lt raw Bandpass Filtering a SEG Y Input SEG D Input SEG B Input SEG 2 Input SCS 3 Input MB1 Drag module Ctrl MB1 Copy module MB1 DblClick Module Parameters MB2 Toggle modu 4 w Screen Display 31 RadExPro seismic software www radexpro com Run it once again to see the filtering result m Zoom Common parameters Vi
52. precompute data tick box and select the database object with the semblances we just have created PS PP velocities Semblance Display Gather Display STCK Display CVS Display Super gather Input velocity Output velocity Semblance Start velocity faw End velocity po Velocity step 5 Time step i Save template Load template OK Cancel You may also want to decrease the semblance display gain to 0 6 as we have done before Now your flow shall look as following Help Options Database Tools Run Flow mode Exit Super Gather Bandpass Filtering A mplitude Correction Screen Display Interactive Velocity Analysis lt semblance_precomputed Velocity Analysis Precompute Trace Output SEG Y Output RAMAC GPR JIOTUC GSSI Input Super Gather Text Output MB1 Drag module Ctrl MB1 Copy module MB1 DblClick Module Parameters MB2 Toggle module Ctrl MB2 DbiClick Delete 47 RadExPro seismic software www radexpro com Run it to get back to the Interactive Velocity Analysis The navigation between super gathers will be much faster now Skip the very first SCDP with incomplete fold and go the next one For navigation you can use either the lt and gt arrow buttons at the toolbar or the drop down list opf all available SCDPs at the top right of the window a File Velocity Field NMO Help gt N Gi elz om x SCDP 100 ILINE 100 XLINE 0 z a500 2000 25 20
53. put data see How To Create Project And Load Data tutorial for the details We name our project OffshoreHiResMultiChan but you can use any other name of course Within the project we created an area named White Sea a line named Line 5 and a flow for data input RadExPro seismic software www radexpro com Help Options Database Tools Exit MB1 DbIClick Default action MB2 Context menu MB1 Drag flow to line PAR Inside the flow we will read the data with SEG Y Input save it as a project dataset we name it raw and save at the Line 5 level with Trace Output and finally display the data on the screen using Screen Display module Help Options Database Tools Run Flow mode Exit SEG Y Input lt linesraw sgy Datal O A Trace Output gt raw Trace Input Trace Output Screen Display APEE N IE SEG Y Output SEG D Input RAMAC GPR SEG B Input OME SEG Input 655 Input 5C5 3 Input Super Gather Text Output Data Output Geometry Headers Header lt gt Dataset Transfer ME1 Drag module Ctrl MB1 Copy module MET Dbillick Module Parameters MBZ Toggle module Ctrl w The parameters of the modules in the flow are shown below RadExPro seismic software www radexpro com Sample format Sample interval 1 05 DAT ASinesraw sgy 1 lat lat Ra Number of traces ja fr IBM Floating Point Trace length 4000 M Use trace weighting factor Big endian byte order SEG Y standard C Little endian byte order Sort
54. re a seafloor pick that we will use later for top muting We will pick the seafloor automatically check the result and edit it when necessary For automatic picking we will need to define 2 things 1 the search gate defined as a start horizon and a search window of a constant length below it and 2 amplitude threshold that will be used for seafloor detection Create a new flow and call it O80 seafloor pick Add Trace Input to input the stack dataset sorted by CDP Add Screen display set number of traces to 2200 to make sure all of them fit the screen Run the flow to see the data on the screen and define the autopicking parameters You can create an approximate horizon above the seafloor to use it as the start horizon however in this particular case it seems to be reasonable to use a constant value of 80 ms for that gate top Then we can search for the seafloor within 40 ms window that is we will be detecting the seafloor between 80 and 120 ms TWTT This iunterval where we will be searching for the seafloor reflection is shown here 57 RadExPro seismic software www radexpro com When you move mouse cursor over the screen note the status bar showing the current trace number sample number amplitude and TWTT H Ba a al gt Ir1635 Sam 2566 Amp 4 88e 003 t 128 3ms Compare the amplitudes at the seafloor and above it If you have used the same processing parameters as we did you will see that the peak amplitu
55. rol Uperator length mg Type of AGC scalar Basis for scalar application E MEAN CENTERED Trace equalization Basis for scaling Time gabe start time me Time gate end time rms MEAN I Time variant scaling Specify amplifying law along trace t me Example format F ETE EEKZ INK 33 RadExPro seismic software www radexpro com The module shall be placed after the Bandpass Filtering and in front of the Screen Display Help Options Database Tools Run Flow mode Exit Trace Input lt raw Bandpass Filtering MPN ma Output Amplitude Correction SEG Input SEG Y Output SEG D Input RAMAC GPR SEG B Input JOC SEG 2 Input GSSI Input SCS 3 Input Super Gather MB1 Drag module Ctrl MB1 Copy module MB1 DbIClick Module Parameters MB2 Toggle mod v Screen Display Execute the flow to check the result Zoom Common parameters View Tools Exit Stop flow 90 668 66850680 gt on a Tr33 Sam 0 Amp 1 42 t 0 0ms lt Again feel free to try out different types of amplitude corrections here and select the result you like most Finally when we are happy with the preprocessing result we need to process the whole dataset and save the result For that first open the Trace Input module at the beginning of the flow at change the 34 RadExPro seismic software www radexpro com selection mask to read the whole range of CDPs Sort Fields Number of Ensemble Fields fi
56. ry Input it is located in the Marine group RadExPro seismic software Help Options Database Tools Run Flow mode Exit Add White Noise Hodograph 2D Finite Difference Modeling Data Filter Comments First Breaks Picking Zero Offset DeMultiple Gas Hydrate Stability Zone Profile Interpolation Travel Time Inversion www radexpro com Lamb Solid Layer Solid modeling Add Event Data Manipulation Auto Picking Marine Tides Import Swell Filter Interpolation Spatial Interpolation Refraction Easy Refraction Surface Wave Analysis MB1 Drag module Ctrl MB1 Copy module MB1 DblClick Module Parameters MEZ Toggle module Ctrl MB2 Dblllick Delete PAR The module name finished with a this means it is a stand alone module so it must be alone in the flow does not requiring any input or output routines Add the module to the flow on the left by drag and drop You will see the module parameter dialog Ship navigation Source streamer geometry Time match 07 11 2013 Julian day 31 1 C Use interpolated coordinates for Header field match Select header FFID Time match mode the following headers ust be filed YEAR DAY HOUR MINUTE he date specified comesponds to the first ine of a navigation file Click the button to the right of the dataset field to specify a dataset in the project database to assign geometry to Select the raw dataset we have cre
57. slsise B B E EIE E aade py 2 als 33l i Ih i ae You may wish to check other values as well or may be check the fold for different CDPs the Marine Geometry Input has calculated it and saved into the TR_FOLD header You can do it yourself if you like we will continue to the next processing step Preprocessing The preprocessing is aimed in improving signal to noise ratio and compensating for amplitude attenuation We will make here only some minimal processing that is absolutely required not to over process the data Additional processing can be added at later stages if necessary Create a new flow 050 preprocessing Add Trace Input module and select sorting keys CDP OFFSET we are going to work with CDP gathers now For parameter tests we will input first 200 CDPs only when we are happy with the parameters we will run the flow for the whole dataset Data Sets Sort Fields Number of Ensemble Fields fi Note Ensembles will be defined by this number of sart fields Delete Add Delete f Selection 1 200 C Select from file File C Database object Choo Cancel C Get all 29 RadExPro seismic software www radexpro com Put a Screen Display at the end Switch on ensemble boundaries option to see the gaps between CDP gathers You may also with to label CDPs along the horizontal scale the same way as we did with FFIDs when we were checking geometry Now the fl
58. t Bandpass Filtering Trace Editing a RAMAC GPR Trace Output gt stack _dgh mpais aniei rroen Display SEG 2 Input GSS Input ere F lmnrrrt Errr foathar MB1 Drag module Ctrl MB1 Copy module MB1 DbiClick Module Parameters MB2 Toggle module Ctrl MB2 DbIClick 2 w Run the flow once again to deghost the data and output the result Migration The data demonstrate rather complex topography and subbottom structure with a number of diffraction hyperbolas so the migration is needed to place refection boundaries to their real positions There are several migration algorithms available in the software We will use the Kirchhoff migration as it allows both vertical and lateral changes of migration velocities Create a new flow 100 migration Help Options Database Tools Exit white Sea MB1 DbtIClick Default action MB2 Context menu MB1 Drag flow to line to copy 71 RadExPro seismic software www radexpro com Enter the flow and add the module called Kirchhoff Migration This is a stand alone module The parameters are shown below Input Dataset White Sealine S stack_dgh Define velocities manual view table Geometry Sample Interpolation p Anti aliasing X step m Y step m Ole a Y Use Antialiasing filter Cosine Triangle BoxCar Angle aperture deg 90 Angle aperture tapering deg 10 x Range aperture m 100 Y Range aperture m 100 Range aperture tapering m 5 R
59. ta before and after the spectral whitening with the F K Amplitude Power The result should look similar to what is shown below the spectrums are zoomed in to 0 5000 Hz interval Before spectral whitening File View Scale Parameters oO f 2127 7 Hz A 78 Aabs f 21776 138 77 RadExPro seismic software www radexpro com After spectral whitening using F K Amplitude Power module File View Scale Parameters 100 n O an 2 f 2184 2 Hz Afl 03 You may wish to try the alternative ways of spectral whitening yourself For example instead of the F K Amplitude Power try to use Spectral Whitening module Plotting Finally let us print the processing result In the RadExPro there is a dedicated stand alone module for printing of seismic sections to any Windows compatible printer or plotter If you install one of the numerous virtual printers available from the Internet some of them are free even for commercial use with or without certain limitations you can use the same module to output the result to PDF JPG BMP and a number of other formats Create a new flow 120 plotting This is the last flow in this tutorial If you have been following all the steps and kept the flow naming your project by now shall look like this Help Options Database Tools Exit O White SeaHline 5 j010 data input MB1 DblClick Default action MB2 Context menu MB1 Drag flow to line to copy 78 RadExPro
60. ule MET DblClick Module Parameters MB2 Toggle moc 2 w This processing step is relatively time consuming it will take several minutes to complete Migration Result and Post Processing Let us check the result of the migration and apply some final post processing if needed Create a new flow 110 postprocessing add Trace Input to input the stack_migr dataset sorted by CDP Add Screen Display number of traces 2300 From T 80 ms Gain 0 2 Froomt lao to lan Boy noes Normalizing factor rom t z t Scale ho OWT ANA i ane Gain 0 3 C WT et ee Humber of traces 2300 NM Scale 10 co vA aa Bias Tu ndividua Rotate None Show every Ensemble boundaries M th trace Variable spacing field Yanable density display mode Normalizing factor Space to maximum ensemble width Grey None Ensembles gap 2 CAE Entire screen Custom Define Individual Muliple panels E C None M Use excursion 2 0 traces Data velocity Display data l l Palette range Display velocity Set velocity l Show headers Min vel ms 500 0 Plot headers Header mark Max vel me 1500 0 Fickspolygons settings Save Template Load Template Ok Cancel 73 RadExPro seismic software www radexpro com Click Axis to set scale parameters Traces C Different di Values Values COP C Interval 100 0 Primary lines R0 f Multiple Secondary
61. wrong parameters you will need to make it once again from the very beginning which takes time as well For this reason what we are going to do now is to first run the IVA in the interactive mode in the flow to make sure that the semblance parameters are correct Then when we are happy with the semblances we will pre compute them for the whole dataset and run the IVA in the stand alone mode 40 RadExPro seismic software www radexpro com When the Interactive Velocity Analysis is added into the flow you will see its multi tab parameter dialog open at the Output velocity tab PS PP velocities Semblance Display Gather Display STCK Display CVS Display Super gather Input velocity Output velocity Semblance Single velocity function t Use file Browse D PASE Database grid Browse Velocity domain Velocity type 6 Tine Depth rs Interval Save template Load template Cancel Here you will need to select where the module will save the resulting velocity function Select Database picks option to save it a database option click Browse button and specify a name for the database velocity pick We will call it v1 and save at the line level Object name A Objects Location E White Sea line 5 l 010 data input O20 geomet agsignemerit 030 geometry check 040 positioning cross plots 050 preprocessing i OBO velocity analysis Rename Delete Cancel
62. ystem from extensive memory usage and creating of swap files Velocity Analysis Create a new flow 060 velocity analysis Help Options Database Tools Exit White Sea MB1 DblClick Default action MB2 Context menu MB1 Drag flow to line to copy In order to obtain more coherent velocity spectra semblances it is a common practice to input the data to the velocity analysis by ensembles containing several adjacent CDP gathers so called super CDPs or super gathers rather than single CDPs For that we will start the flow with a Super Gather module X Start gt X End Ze X Step fo X Range 5 Y Start fo Y End fo YStep JY Range fp Off Stat J Off End Off Step fo Off Range fo Save template Load template Cancel 36 RadExPro seismic software www radexpro com Here we select preproc dataset for the data input Then we indicate starting and ending CDPs X Start 0 and X End 2216 as well as the interval in CDPs between the neighboring velocity analysis stations X Step 100 and a number of adjacent CDP gathers to be included into each super gather X Range 5 NOTE We know that the seafloor bathymetry along this line is changing abruptly so we select only 5 CDPs per super CDP otherwise CDPs from very different places will get mixed together disturbing the resulting semblances If when you process your data the bathymetry is less sharp you may try to increase the number of CDPs per sup

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