dip3d Computing Structural Dip Program dip3d Computation flow chart Volumetric Attributes: Program dip3d

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1 Comuting Structural Di Program di3d Comutation flow chart Program di3d uses a seismic amlitude volume as its inut and generates estimates of inline di, crossline di, di magnitude, di azimuth, and a confidence measure of these estimates The inline and crossline di comonents are critical for almost all subseuent AASPI comutations The di magnitude and di azimuth are useful if you wish to dislay di azimuth modulated by di magnitude using the multiattribute dislay rograms hllot, hslot, hlslot, or corender The confidence volume is used to remove artifacts in the di volumes using rogram filter_di_comonents Initially, these inut seismic amlitude volume would be either your time- or deth-migrated amlitude or acoustic imedance However, as we rogress through the AASPI software, we shall wish to recomute the di comonents from the data that have been subjected to structure-oriented filtering using the rogram sof3d, or have been sectrally balanced using the rograms sec_cm or sec_cwt Seismic amlitude di3d Inline di Crossline di Confidence Di magnitude Di azimuth Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page

2 Parameter descrition To begin, at the to of the aasi_util GUI, click the Volumetric Attributes tab, located to the right of the File tab A down dro menu will aear containing the major AASPI rograms di3d, filter_di_comonents, similarity3d, sof3d, curvature3d, aarent_cmt, euler_curvature, glcm3d, and disorder In general, we will roceed from to to bottom, with the outut of di3d being reuired inut for similarity3d, sof3d, curvature3d, and glcm3d AASPI has AASPI Workflows (Batch Mode), with which you can run set of rograms in seuence with one click, which saves time and effort The outut of sof3d can be used for either di3d or similarity3d, roviding iterative structure-oriented filtering caabilities The following GUI should aear: Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page

3 Click () Browse, and select d_mig_gsb_smallh as your inut seismic data set You also need to () choose a uniue roject name, which will be tacked on to an attribute descritor to organize the outut We urosely used the roject name reviously used in the conversion from segy to AASPI format, but this is not necessary Tye in GSB_small Then (3) select a Suffix If this is the original migrated data and you wish to distinguish between it and a data volume that has gone through two asses of structure-oriented filtering, you might give this run a Suffix = 0 or Suffix = orig, and the nd run a Suffix = c_ Under the Primary arameters tab, note that the default di search will be from -0 0 to +0 0 at increments of 5 0 The reflectors in the GSB_small survey are very flat, rarely exceeding 5 0 Therefore, set the value of (4) Theta Max = 5 0, and (5) Delta Theta = 3 0 The discrete searches will occur over inline di comonents,, and crossline di comonents,, forming a radial grid of discrete dis as described in the algorithm imlementation box Thus, for the values of 5 and 3 above, there will be 9 discrete semblance evaluations along candidate dis Doubling the di search range (Theta Max) but retaining the same search increment (Delta Theta) would uadrule the comutational effort Note that this search is more exhaustive than that rovided in commercial algorithms which limit the search to inline and crossline ((5++5)+(5+5)= discrete semblance evaluations The more exhaustive search rovides suerior results for aliased data and very stee dis Alternatively, you might wish to comare the effect of values of (5) Delta Theta, or of window size of 0 ms and set your suffix to dtheta_5 or window_0ms Remember that you will need to use characters that can form a valid Linux file name (no = lus signs, slashes, blanks, etc) Also, remember that the binary files are being stored in a directory defined in file ~/dataath Even if you run rograms from different directories, files with the same name will overwrite each other in the directory defined by dataath If you wish, you can coy and modify the contents of dataath in your local roject directory This local version of dataath will take recedence over that in your home directory The Conversion velocity (6) is read in from the file aasi_default_arameters, which is currently set to be 4,000 m/s for data measured in m For the GSB_small data, we may wish to use a slower velocity of about 3,000 m/s You will always wish to (7) comute the inline and crossline di comonents, so this box is disabled In contrast, you may or may not wish to comute in (8) di magnitude or (9) di azimuth Let s check this to see what it rovides Want di confidence result? is chosen by default since it will be reuired if you run rogram filter_di_comonents Asking for any of these files does not influence the run time, just the disk sace used Proceeding to the Analysis window arameter tab: Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 3

4 By default, the Di window height will be ±5 samles (for the GSB survey with t=0004 s, ±000 s), and both the () Inline window radius the (3) Crossline window radius will be one trace (in this case, 5 m by 5 m) or 5 traces total If you select (4) the Use rectangular vs ellitical window? otion, you will define a rectangular window, which for this examle contains nine traces Larger windows result in smoother di estimates with a comutational cost roortional to the number of traces that fall within the window For this reason, comutations using rectangular windows run 8 times longer than those using ellitical windows with the same radii The following boxes Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 4

5 rovide more detail on the window definition, the angle definition, and the angle interolation used within our imlementation Imlementation details: Analysis window descrition in the AASPI software Almost all of the AASPI geometric attributes are comuted within a running analysis window Tyically these windows are defined by their length and width in m (or ft) and height is s (or km, kft, m, ft), and are oriented along structural di and azimuth The figure below shows a tyical rectangular analysis window Let s assume the trace searation is dcd=5 m in the inline direction and dline=5 m in the crossline direction If you wanted to have the same di resolution in both directions you may choose an inline_window_radius=*dcd=5 m and crossline_window_radius=dline=5 m The rogram default is to set the window radii to be the inline and crossline trace sacing (bin size) resulting in a 5-trace analysis circular window Larger analysis windows result in longer run times, increased angular resolution, and decreased satial resolution (smearing) If the data are noisy, a circular window radius eual to bins is a good lace to start, resulting in a 3-trace analysis window if dcd=dline The window on the uer right corresonds to a survey with dcd=5 m and dline=5 m A circular window with inline and crossline radii of 5 m therefore contains 7 traces If we lace a check mark in the Use rectangular window? otion, we will obtain the window on the right which contains 5 traces Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 5

6 Imlementation details: Discrete di search Earlier versions of the AASPI software comuted the analytic semblance on a suite of rectangularly defined inline and crossline dis, ranging between -θ max θ x +θ max, and θ max θ y +θ max Di magnitudes that fell beyond θ max are used to hel interolate but otherwise rejected As of February 06, di3d uses olar-defined search angles as shown in the image below For a given angle, density (defined by the angle increment, θ, this new search algorithm uses % fewer angles, resulting in an eual imrovement in run times More imortant, surious interolated angles that fall beyond θ max are avoided Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 6

7 Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 7 Imlementation details: Angle interolation The first ste in di estimation is to search over discrete angle Note in the image below if the angle with the largest semblance is the red angle, it has eight neighbors In contrast, if the angle with the largest semblance is the green angle, it has six neighbors In either case, we define a arabola that intersects each of the neighboring oints of the form ), ( s This euation is evaluated at each of neighboring (8 or 6) discrete angles as well as the center angle, numbered,,,n, to obtain n n n n n n n s s s , or in matrix form, s Pα, with the solution s P I P P α T T ε The maximum of the arabola is found by setting 0, 0, a a a s a a a s and solving the resulting x euation using QR factorization

8 Imlementation details: Structure-oriented analysis All of the AASPI geometric attributes are comuted along structural di The same holds true for the initial search for inline and crossline di comonents While the vertical_window_height arameter defines the half-height of the analysis window, the window itself will always be centered along di, as in the following image: A good rule of thumb is to select a vertical window about the size of the dominant freuency in your data Thus, if your dominant freuency is 0 Hz, the dominant eriod is 0050 s, suggesting a halfwindow height of 005 s If your dominant freuency is about 50 Hz, giving a eriod of 000 s, you may wish to use a half-window height would be 000 s The default is to set the half window height to be 5* t, where t is the seismic samle rate in unit (eg ms, s, ft, m, kft, km) In contrast to the window radii, the window height does not significantly imact run times, but larger windows can result in vertical smearing If your data are articularly noisy, you will want to use larger vertical analysis windows, at least until you have the oortunity to run structure-oriented filtering Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 8

9 Imlementation details: Kuwahara windows Programs di3d, sof3d, and sof_restack all use a modification of overlaing window arameter estimates introduced by Kuwahara et al (976) in medical imaging The original idea is simle If an analysis window contains five traces, then there are total of five windows (a centered window and four adjacent, offset windows) that contain the analysis oint In Kuwahara et al s (976) original work and Luo et al s (00) edge-reserving smoothing algorithm, one calculates the mean and standard deviation of each window That window which has the smallest standard deviation is hyothesized to be less noise-contaminated The mean of this window is then used as the outut for the analysis oint Marfurt (006) modified this aroach for volumetric di calculations where he used 3D rather than D overlaing windows In addition, the semblance of the analytic signal is used rather than the standard deviation to determine which window is least contaminated by noise The inline and crossline comonents of reflector di of this best window are then assigned to be the outut at the analysis oint The figure in the lower left reresents a 3-trace circular analysis window centered about the analysis oint indicated by the red solid dot Each of the traces reresented by the green dots in the figure in the lower right form the center of their own 3-trace analysis windows, yet contains the trace reresented by the red dot The window having the highest analytic semblance best reresents the signal; its di comonents are therefore as the di at the red analysis trace For reasonably good uality seismic data, lace a checkmark to (6) search lateral windows If the data are very noisy, using Kuwahara windows can give rise to a atchy aearance on the di comonents If such blockiness is unaccetable, remove the checkmark in front of search lateral windows For very oor uality seismic data, lace a checkmark in front of (5) search vertical windows This otion will also introduce some blockiness, but avoids smearing angular unconformities, onla, tola, and other configurations imortant to seismic stratigrahy interretation To minimize the atchy aearance that can occur when using Kuwahara windows, (7) set a threshold value of the analytic semblance, s_uer=085 If the semblance of Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 9

10 the centered window is greater than the value s_uer, its value of di and azimuth will be used If the semblance is less than this value of s_uer, the Kuwahara window concet will be imlemented, with the di comonents of the (centered, laterally offset, or vertically offset) window having the highest value of semblance assigned to the analysis oint A deeer discussion of Kuwahara windows can be found in the documentation for rogram sof3d Execution After selecting all your arameters, tye Execute di3d Intermediate outut comes to the xterm from which you launched aasi_util as well as in the file di3d_gsb_smallout Some of the outut aears below: The comutation is comuted using a stencil, with the amount of work divided eually across (in this examle 4 rocessors or core) Thus, the 00 CDPs of the survey are sread eually across the 4 rocessors, most working on 4 CDPS, the others on 4 CDPS As each seismic line is comleted, the results are sent to master rocessor (rocessor 0), saved in an array, and written to disk Progress of the rogram is shown in the bottom of the file above where the master node (indicated by the refix 0: ) indicating the first_line_out, current_line, and last_line_out and an estimated time of Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 0

11 arrival (comletion) ETA measured in hours Near the bottom of the *out file you will see information like this: which give some comutational statistics for each rocess (in this case rocess 0, with a wall clock time of 069 hrs Memory is deallocated, and each rocess echoes out that it has comleted normally: We ve already discussed the di3d_gsb_small_0out file that is a coy of the results that came to the screen di3d also has created the following files: Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page

12 As described in the documentation on the AASPI software environment, each of the AASPI-format files inline_di_gsb_smallh, crossline_di_gsb_smallh, di_azimuth_ GSB_smallH, di_magnitude_gsb_smallh, and conf_gsb_small_0h, (the history files) will have a corresonding *H@@ (header file format) in the local directory, and corresonding *H@ (binary results), and *H@@@ (binary trace headers) that reside in the directory you defined earlier in the dataath file We can lot our di comonents to QC the results by clicking () the AASPI QC Plotting tab in the aasi_util GUI: where () the file inline_di_gsb_small_0h is selected and () will be lotted as time slices: Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page

13 We have also comuted volumetric estimates of di magnitude and di azimuth Using AASPI rogram corender (under the Dislay tab) where () the base layer is set to be Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 3

14 () the di _azimuth lotted against (3) a cyclical color bar with values ranging between (4) and (5) Change the default title to reresent the images co-rendered Then (6) click the tab for layer, and then (3) chose the di magnitude file which will be lotted against (8) a monochrome gray color bar with (9) transarency set such that high values of di magnitude will be transarent, allowing the underling di magnitude value to show through Finally, (0) set the default di magnitude color range to be Smaller ranges will result in brighter colors You should obtain the following image: Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 4

15 To co-rendering with energy-ratio similarity (comuted in rogram similarity3d), return to rogram corender and () choose the Layer 3 tab, () select the energy-ratio similarity volume, (3) lot it against a monochrome black color bar, and (4) set the high coherence values to be transarent, allowing the underlying co-rendered di azimuth vs di magnitude images to show through Finally, (5) adjust the range of the similarity and (6) modify your lot title: Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 5

16 The following image should aear: One can also lot the results in the vertical slice As before, use di azimuth as the base layer, lotted against a cyclical color bar, di magnitude as the second layer lotted against a monochrome gray color bar, with high di magnitude values transarent, but now in rogram corender, under the Layer 3 tab, () select the energy-ratio similarity volume, (3) lot it against a binary black white color bar, and (4) set the low values about amlitude zero crossings to be transarent, allowing the underlying co-rendered di azimuth vs di magnitude images to show through Next, (5) choose Statistical Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 6

17 Ranging of the color bar, and (6) set the Percentage Cli =90, so that the color bar ranges between the 5 and 95 ercentile ranges of the amlitude data Finally, (7) modify your lot title and lot vertical slices: Here are two reresentative images: Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 7

18 at an aroximate : scale, using the value of velocity used in the calculation: Using rogram aarent_cmt, we can comute aarent di at any arbitrary azimuth, φ, using the simle formula a (φ)= cos(φ)+ sin(φ) The aarent_cmt GUI is simle: where here, the GUI asks to comute aarent dis between 0 0 and at 30 0 increments, resulting in six files: Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 8

19 Note that if one comuted to that the next six values will be numerical inverses of those in the oosite direction The inline azimuth of the GSB survey is +5 0 while the crossline azimuth is oriented clockwise at Plotting the results of aarent_cmt at the same time slice, we see the inline and crossline di comonents correctly lotted at 0 0 and 90 0, along with the other comonents Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page 9

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21 Notice, there are some small glitches in di estimation We can comute the confidence that we have at each voxel of the di estimate Since rogram di3d uses a Kuwahara multile overlaing window di search, the confidence is simly the coherence (in this case semblance of the analytic data) of the window used Overall, this is a high uality seismic data volume Not surrisingly, the lowest confidence is adjacent to the major discontinuities Deeer in the survey, we some areas (seen as black) where our di estimates are less accurate: Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page

22 We will try to further imrove our di estimates with some simle median filtering using rogram filter_di_comonents References Davogustto, O, and K J Marfurt, 0, Footrint suression alied to legacy seismic data volumes: to aear in the GCSSEPM 3 st Annual Bob F Perkins Research Conference on Seismic attributes New views on seismic imaging: Their use in exloration and roduction, -34 Kuwahara, M, K Hachimura, S Eiho, and M Kinoshita, 976, Digital rocessing of biomedical images: Plenum Press, Luo, Y, S al-dossary, and M Marhoon, 00, Edge-reserving smoothing and alications: The Leading Edge,, Marfurt, K J, 006, Robust estimates of reflector di and azimuth: Geohysics, 7, 9 40 Attribute-Assisted Seismic Processing and Interretation - 3 January 07 Page