Processing Lab 2 – Geometry Bryce Hutchinson Objectives: Add a dictionary Gain a better understanding of header issues Display geometry correctly Visualize shot and receiver pairings Sort Traces by offset

Reopening your project First of all, if you are on a different computer than last week, you will likely have to fix the licensing issue again. You will know if this is a problem if Vista says DEMO at the top. If it does not say DEMO, move on to the next slide! 1. Click license, then from the drop down menu choose “Options Soft/Hard Key” 2. A window opens up displaying some licensing options. Check the box that says “RLM Reprise Soft Key”. Click OK.

Reopening your project 1. Click File then Open Project… 2. Navigate to the correct directory where you saved your project. This should be on your own portable hard drive or USB. My project is called ‘Stratton_class_bh.vwn’ 3. Click Open and let’s get to work

Adding a dictionary 1. At the top of the Vista window, click Dictionary. Then click Edit Input Dictionary 2. Here is your dictionary, it displays all the important values for the seismic data, the size of the data, and where it is located within the SEGY file. The standard SEGY dictionary is not what we want to use for our project. So we will read in a new dictionary file. 3. Click the open file button at the top left of the window.

Adding a dictionary 1. Navigate to where you save the stratton_dict.dic file you received today. Open this file. A new dictionary file appears. It is titled NEW SEG-Y Revision 1 2. Click Save Defined Dictionaries to Project. 3. Close the window. You are are prompted again to Save here. Click Save.

Loading new data Now we will fix a problem that was created last week…welcome to the world of processing! We need to delete the data that was loaded next week and add a different dataset. 1. Click the red minus sign at the top left of the project data set window. 2. A window appears asking if you want to delete this data set. Click OK

Loading new data You will now have a blank project data set window. 1. Click the 3D button to add a new dataset. This is just like what we did last week. 2. Open d_sg_stratton3d

Loading data – Header comparison 1. Click the Trace Header tab, from here we can get an idea what issues incorrect headers can cause. 2. Choose SEG-Y Revision 1 for the Dictionary type. This is the type of dictionary we would use if we hadn’t mapped our own. 3. Type in into the Trace# input, take note of the inline number. Now type in into the Trace# input. You will notice the In_Line values are repeated…because this is actually Field_Station_Number incorrectly mapped.

Loading data – Header comparison 1. Change the Dictionary to [12] NEW SEG-Y Revision 1 2. Field_Station_Number now appears where In_Line previously did. If you scroll through the traces, you will notice that the values no longer repeat. 3. BE SURE that you have [12] NEW SEG-Y Revision 1 selected for the dictionary before clicking OK. If you do not, that will only bring more headaches, and we really don’t want that! Note: We will still have an In_Line error when we finish loading the data. However, this is because we have not applied geometry to the data yet.

Loading new data 1. Click the dropdown menu for Trace Header Dictionary. Select the dictionary we just added: NEW SEG-Y Revision 1 2. Click OK 3. The data will load for a few minutes and you will receive an error. Click OK and exit out the window that is open.

Accessing the Geometry 3-D Window 1. Click the icon that looks like cross cutting red and blue lines. This will launch the geometry window. 2. Click Load on the next window that opens up. 3. Another window appears after you click load. Click OK

Geometry View A window opens with a very vague geometry outline. Let’s make this a little easier to look at. 1. Right click in the geometry display and click Shot Display Parameters 2. Change the symbols size too 100 FT. Click OK. 3. Right click on the geometry display again and this time click Receiver Display Parameters. Change the size to 100 FT. Click OK. The resulting image is on the next slide

Geometry View It is now easier to see in this window the shots and receivers. Shots are represented by red squares. Receivers are represented with blue and yellow crosses. 1.By clicking through the different templates, you can scroll through the shots which will be highlighted in an aqua color. The receivers that were recording when that shot was taken are highlighted in yellow. 2. Minimize the Geometry window to return to the main data set window. 3. Click the seismic window icon to display the traces for this data.

Binning 1. Click the Binning icon to launch the 3-D Bin Grid Layout 2. Enter 360 as the azimuth. This will line the grid up north-south with the majority of the data. 3. Set the IL-bin size and XL-bin size to 55. This is half the distance of the receiver spacing. 4. Check the boxes for Lock Azimuth and Lock Bin Size. Uncheck the boxes for Center on In-Line and Center on X-Line. Click Auto-Calculate. Click OK. Note: Binning is essential to any calculations performed on the geometry. Binning sets a grid in which CMP (Common Midpoints) can be grouped.

Binning The bins we created are now displayed in the geometry window. 1. Click the calculator icon on the left side of the screen 2. Check the Fold File box and the Offset File box 3. Click OK Note: Fold is a measure of the coverage of an area. You want high fold. Both fold and offset must be calculated before displaying CMPs.

Binning 1. Click and drag in the geometry window to zoom in. Zoom in on an area about the size I’ve shown here highlighted in blue. 2. Right click in the geometry window. In Overlay Display Options, click Mid-Point 3. The midpoints between each shot and receiver are now displayed. However, there is a problem. The points fall very close to the edges of the bins and we want them in the center of each bin.

Binning 1. Click the 3-D Binning icon again. 2. Set the IL offset to be 27.5 (half the bin heighth). Click OK. 3. The new images contains the CMPs well within the confines of each individual bin. Note: You will notice that some bins are empty. This is because the shot spacing is twice the receiver spacing. However, the bin must be square otherwise later migration will smear the data.

Binning Every time the binning grid is changed, the fold must be recalculated. The bins we created are now displayed in the geometry window. 1. Click the calculator icon on the left side of the screen 2. Check the Fold File box and the Offset File box 3. Click OK Note: Fold is a measure of the coverage of an area. You want high fold. Both fold and offset must be calculated before displaying CMPs.

Display 1. To zoom out, double click anywhere in the zoomed in geometry window 2. Right click in the geometry window, Click to Display Bins to turn off their display 3. Right click again and turn off the Mid- Point display 4. You are now returned to a fairly simple display of only shots and receivers

Fold Display 1. Click the Change Display Type icon to bring up the Display Fold/Azimuth/Offse t window. 2. Click the circle in front of Fold. Click OK 3.The fold is now shown in the geometry window. Our data shows a maximum of 24 fold. If you prefer a cleaner image you can turn off the shot and receiver display by right clicking and unchecking Display Shots and Display Receivers.

Spider Display 1. Return to the Display Fold/Azimuth/Offset menu and click None to turn off the fold display. Click OK 2. Check Spider, In Color, and First Diff. Click OK 3. Zoom in very close on the new image to display only a few bins 4. Now displayed are the spider diagrams for each bin. Spiders show the azimuth distribution for a bin and the colors signify the length of the offset.

Saving the Binning 1. Click and hold the floppy disk icon then click Save Bin Grid Information to Data Set 2. Click the floppy disk again and click Write Binning Info To Headers 3. A save window pops up. Click OK

Display 1. Return once again to the Display Fold/Azimuth/Offset window and turn off the Spider. Click OK 2. Double click in the geometry window to zoom out and return to the normal shot- receiver display.

Shot broadcasting 1. Now let’s take advantage of our dual monitor display. Expand Vista across both of your workstation screens and display both your geometry and seismic trace window. 2. Right click in the geometry window. Under Mouse Mode, Click Shot Broad-Cast

Shot broadcasting Double click any shot (red square) and display the traces that were recorded at each receiver for that shot. Traces display differently based on their offset from the source. I have added the aqua colored squares to the images here so that you can see the general shot location and how it corresponds to the display.

Shot broadcasting 1. The offset for each receiver line is displayed at the bottom of the seismic window. Notice how first arrivals appear earlier at smaller offsets. 2. Click the plot Trace Mode button to sort by Offset. 3. Notice the continuous increase in offset once your traces have been sorted