The SEG-Y trace header preview reads SEG-Y files from the UK NDR and the user's local disk. The tool displays the different parts of the SEG-Y files, such as textural, binary, trace header, and trace preview for local files.
The preview of SEG-Y trace data and headers in the UK NDR launches from the right mouse context menu on SEG-Y files in the files table in the NDR online interface.
The local SEG-Y file reading version is launched from the “Local SEG-Y preview” option in the “Data submission” drop-down menu in the NDR online interface.
SEG-Y datasets can be large, and reading trace headers for the whole volume could use all available memory on your device. To avoid this, user-adjustable limits are set for how much of the dataset to read and display at once. The amount of data viewed at once can be adjusted using the Settings option from the main menu (three-line menu icon).
To control which part of the SEG-Y file is being viewed, there is a slider bar at the bottom of the window that displays how much and where in the SEG-Y file is being displayed; the width of the bar changes to show the proportion of the dataset being viewed. For smaller datasets, this will be set to the entire width of the slider and the whole dataset is shown. For larger datasets, the bar will be a proportion of the total width of the slider and can then be dragged with a left click or other pointing device to the part of the dataset that must be loaded.
When previewing the SEG-Y trace headers the tool opens in a new window with a spreadsheet view of the trace headers in different number formats. The rows in the sheet represent the traces, and the columns are the trace header locations in bytes. In the header of each column, there is a tick box, and selecting this will draw the graph of that trace header against the trace number.
Some of the columns have a coloured header cell and will display Pkey, Skey, Xkey, and Ykey. These are automated suggestions for which headers may be the primary and secondary, sorted trace headers, and the X/Y trace headers.
To investigate local files from a cloud preview tab, select the “Read local SEG-Y file” option from the main menu.
This will open a new browser tab with an open Segy file button next to the main menu.
Clicking the “Open SEG-Y file” button will open a file selection window, allowing you to navigate to and select the SEG-Y file you wish to investigate.
SEG-Y trace header displays
The dropdown menus at the top of the window allow access to different views and displays, and file settings can be edited from the main menu (three-line menu icon). Hovering over each option on the dropdown menus shows a short description of its functionality.
Trace Headers
The trace headers are read as int32, int16, and ibm float number types and displayed in table format for user examination. The rows in the table represent the traces, and the columns are the trace header locations in bytes. Only columns of non-zero trace headers are shown in the table. The tabs at the top of the table allow the user to swap between the different number types displayed in the table.
In the header of each column, there is a tick box. Selecting this will draw a line graph of that trace header against the trace number; unticking the box will turn off the graph for that column.
When reading SEG-Y from the NDR, some of the columns have a coloured header cell and will display, Pkey, Skey, Xkey, and Ykey. These are an automated suggestion for which headers may be the primary and secondary, sorted trace headers and the X/Y trace headers.
File Info -> EBCDIC Header
This option displays the SEG-Y file Textual header from both ASCII and EBCDIC encoding
File Info -> Binary Header
This option displays a summary table of significant values from the binary header.
File Info -> Metadata
This option displays a summary table of the file's significant metadata from the NDR database. It is not available for local SEG-Y files.
Plot parameter toolbar
The plot parameter toolbar, located at the bottom of the window, controls the parameters for the different trace header and data plots.
This allows the user to select which trace headers they plot. If there are suggested Pkey, Skey, Xkey, or Ykey headers, then they will be automatically selected in the drop-down selectors. If these are not the correct or required headers to plot, just click on the selector and choose a different header from the dropdown list.
The toolbar has different elements depending on which plot is displayed. The dropdown lists are used to select 3 headers to plot against each other. For 2D plots, the colour value selector controls which header is displayed as the colour, and for 3D plots, this controls both the colour and the positioning on the Z axis.
SEG-Y datasets can be large, and reading trace headers for the whole volume could use all available memory on your device. To avoid this, user-adjustable limits are set for how much of the dataset to read and display at once. The amount of data viewed at once can be adjusted using the Settings option from the main menu (three-line menu icon).
To control which part of the SEG-Y file is being viewed, there is a slider bar in the plot parameter toolbar that displays how much and where in the SEG-Y file is being displayed; the width of the bar changes to show the proportion of the dataset being viewed. For smaller datasets, this will be set to the entire width of the slider, and the whole dataset is shown. For larger datasets, the bar will be a proportion of the total width of the slider and can then be dragged with a left click or other pointing device to the part of the dataset that must be loaded.
SEG-Y files from the NDR are loaded in parts (each part is 1 Gigabyte of the SEG-Y file), while local SEG-Y files are loaded by trace number in the SEG-Y file. The maximum number of parts or traces to be loaded at once is user-defined in the Settings option from the main menu. The number of parts/traces to read is dependent on your device's memory.
The first and last part/trace numbers are shown underneath the slider bar; in the middle, underneath the slider bar, is the current part/trace number.
The min and max values for the colour scale are automatically determined for plots but can be manually defined from the Min and Max boxes on the plot parameter toolbar and applied by clicking on the Apply button next to them.
For local SEG-Y files, there is a trace plot option that enables an ‘instantaneous automatic gain control’ (IAGC) option on the plot parameter toolbar; various window sizes are selectable and will produce a more amplitude-balanced display if required.
Plot colour scales
The 2D and 3D plots all show a colour scale and the default changes with plot type. The user can select alternate colour scales from a popup menu by clicking on the colour name shown beneath the colour scale bar. Colour scales can be reversed after selecting the “Flip Scale” option on the same popup menu.
Plot interaction toolbar
The 2D and 3D plots all show a small icon toolbar on the plot to control the interaction with the plot and take screenshots of the plots.
The camera icon will save a screenshot of the plot while the magnifying glass is selected, allowing the user to select a rectangle on the plot to zoom into. The four arrow pan icon, when selected, allows the user's mouse movements to pan the plot, this is useful when zoomed in to the plot. The plus and minus icons allow for a zoom in and out on the centre of the plot. The house icon will reset the plot back to its original axis scales.
Header Plots -> Inline Xline Surface
The surface plot displays a regular grid such as inline, crossline, and the value of a header as the colour. It could also be other headers such as shot, channel, and a header value. The plot displays in 2D areal view and 3D view as selected by the 3D/2D toggle button in the plot parameter toolbar.
Alternative colour scales to be used in the plot can be selected from a popup menu by clicking on the colour name beneath the colour scale bar. Colour scales can be reversed by selecting the “Flip Scale” option on the same popup menu.
2D view—This surface plot displays Inline and Crossline locations, where the colour represents the value of the byte 33 header at each location. This post-stack example shows that possibly two different datasets were merged into this dataset, as they have very different header value distributions.
3D view—This surface plot displays the same data as the previous 2D plot but is now plotted in 3 dimensions. Each value of Byte 33 is used both for the colour scale and the Z-axis location.
Header Plots -> X Y Z Scatter
The X Y Z scatter plot displays irregular non-gridded data points such as X and Y coordinate headers as individual points on the plot. The colour of the point is set by the value of the third trace header selected. When zoomed out, the plot will appear continuous as the points overlap. When zoomed in, the individual points will be visible. When points have repeated X and Y locations, e.g. pre-stack traces, many points will be plotted on top of each other with only the last visible. There is a ‘Fold’ option in the colour value dropdown selector. This will calculate the fold for each repeated X-Y location and use the fold value for the colour of each point.
This scatter plot displays the same data as the previous surface plots but is now plotted in X,Y coordinates, where each value of Byte 33 is used for both the colour scale and the scale.
This scatter plot for a pre-stack shot domain SEG-Y file displays the receiver X and Y trace headers plotted against the value of the offset header at each location. The colour bar shows the range of offsets, and each receiver location is coloured by the offset header value.
This scatter plot for the same pre-stack shot domain SEG-Y file as the previous scatter plot, displays the source X and Y trace headers plotted with the fold value colours at each location (as selected in the dropdowns on display). This example is a marine shot dataset; the fold is the number of receivers of each source point.
Trace Plots -> Timeslice
For SEG-Y files in the UK NDR, a subset of seismic amplitudes at a constant time or depth are stored for each part of the file (a part is a 1 Gigabyte chunk of the SEG-Y file). The Timeslice option allows the user to select trace headers for Inline and Crossline and then a time/depth slice level to display as a 2D surface plot of the seismic amplitude. The parts displayed in the plot are controlled by the slider bar, and the maximum number of parts can be loaded at once in the Settings option from the main menu.
Trace Plots -> Frequency
For SEG-Y files in the UK NDR, an average frequency content is calculated for the whole trace for each part (1 Gigabyte chunk of the file) of the SEG-Y file. The plot displays a separate frequency against the amplitude curve for each part and shows how spatially variable the frequency content of the SEG-Y file is.
Trace Plots -> Traces
This tool can display the trace data for local SEG-Y files. For files based in the UK NDR, to view the trace preview, please use the alternate seismic data preview tool from the files table in the UK NDR.
The Traces viewer displays most varieties of SEG-Y files as it does not require selecting trace headers. It plots a continuous linear group of traces from the SEG-Y file. The user can select where in the file they view using the slider bar on the plot parameter toolbar. The number of traces plotted is controlled by the Settings option in the main menu. An ‘instantaneous automatic gain control’ (IAGC) option is available from the plot parameter toolbar. Different window sizes are selectable and produce a more amplitude-balanced display if required.
Traces display of a shot domain pre-stack SEG-Y file. Traces are plotted starting at trace 224951, as shown in the trace slider bar located within the parameter toolbar at the bottom of the plot.
Traces display a post-stack SEG-Y file, and traces are plotted starting at trace 607407, as shown in the trace slider bar located within the parameter toolbar at the bottom of the plot.
Traces display of a post-stack SEG-Y file. Traces are plotted with a 400ms IAGC applied.
Main menu
The main menu allows access to other functionality and is opened by hovering over the three-line menu icon on the right hand side of the menu bar, as shown in the figure below.
Main menu -> Read local SEG-Y file
This option will open a new browser tab with the tool in local SEG-Y file reading mode, a local SEG-Y file can then be opened by clicking on the “-> Open SEG-Y file” button to select the file to investigate.
Main menu -> Hide table
This option will hide the trace headers table in case more room is required to display the trace header line graphs.
Main menu -> Settings
This option will open the settings modal dialog box. This allows the user to change the amount of data read and displayed for the different plots. The amounts are in parts ( 1 Gigabyte chunks) for data from the UK NDR and in Gigabytes for local SEG-Y files. The amount of data a user can read and display at once is dependent on the free memory available on the user's device. The number of traces to be shown in the 3D surface plot can also be changed as this is dependent on graphics memory available on the users device.
For local SEG-Y files the user can also control how many SEG-Y traces to display in the Traces plot.
Main menu -> Support Centre
This option will open a new window displaying the UK NDR support centre where this documentation is hosted.
Examples of SEG-Y QC using trace header plots
Surface plot of a corrupt file
This surface plot displays Inline and Crossline locations where the colour represents the header's value at each location. The white blank zone across the middle is an area where the storage on the disk is corrupt, and this middle range cannot be read from the disk. The program has read past this error, and the problem area is clearly shown on the plot.
Spatial distribution of data in a SEG-Y file
The timeslice plot can be useful for showing the spatial distribution of traces in a SEG-Y file. The example below shows the many areas with no data in the selected SEG-Y file. Making timeslice plots of large SEG-Y files with many parts from the NDR requires multiple Gigabytes of free memory on the user's device.
Comments
0 comments
Article is closed for comments.