Processing Lab 3 – Header issues and trace editing

Bryce Hutchinson

Objectives: • Fixing elevation issues • Define an LMO function• Pick first breaks• Kill traces • Construct a flow • Create a notch filter

Reopening your projectFirst 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.

Elevation1. Let’s go back to the Geometry window, by clicking the geometry icon . As you’ve heard numerous times, geometry is critical to good seismic processing. 2. Press Load to load the geometry from the headers that we created in the last lab. 3. Click OK

Elevation1. Right click in the geometry window then click display bins to turn off the bin display.

2. Click the calculator button on the left side of the window. 3. In the Calculation window that appears, check Fold File and Offset File. Click OK

4. Right click in the window, under Display Mode select Shot/Recv Elevations. If you want to you can click receiver elevations instead. The displays do not vary much.

Elevation 1. Now you’re looking at a color fill display showing the elevation of each shot. Notice the color bar ranges from 0-99ft. So does it make sense for there to be areas of 0 elevation surrounded by areas of 99ft of elevation?Or to have such a steep dropoff at the Northwest portion of the dataset? No! We’ve got another issue to fix! Alright!

Elevation1. Exit out of the geometry window. Click Discard.

2. Click the Header icon next to your input dataset. This will bring up the Header View/Edit window, where we can view values from the data in a spreadsheet format.

If there are any columns displayed initially in the Seismic Header View/Edit window we need to remove them. 3. Right Click on the header title 4. Click Remove ALL Columns

Elevation

Let’s add some columns now to evaluate the elevation. 1. Click the drop down window.2. Scroll down until you find ELEV_SHOT. Click this input3. Click the green plus sign to add ELEV_SHOT to the display. 4. Repeat this step for ELEV_REC

Scroll through the elevations some and you will see that the majority of values range from 85-100ft. However, some are single digits. Seems fishy to me.

5. Click the Header Function Icon and a new set of icons appears along the left side of the window.

6. Click the Define Header Mapping for Header Transfer icon and a new window opens.

ElevationAdd ELEV_SHOT and ELEV_REC to this window in a similar way to the previous

1. Choose the input from the dropdown list. 2. Click the green plus sign to add the data to the Header list.

3. Click the white box between Header Name and Comments in the Elev_Rec 4. Click Condition 5. Change the parameter to

ELEV_REC6. Set the Condition to Less Than7. Set the Value to 20 8. Click OK

20

Elevation

1. Click Constant2. Enter 100 into Constant Value3. Click Add Constant4. Click OK

5. Click the white box between Header Name and Comments 6. Repeat the process from the previous slide to adjust ELEV_SHOT.

1. Click the floppy disk icon to save your Header mapping to a file. Name it something like Elevation 2. Exit the window – if you are prompted to save one more time, then save.

Elevation1. Click Apply

Scroll through the data now and you’ll see that all of the values now fall into a more reasonable range.

Return to the geometry window to view the results.

2. In the geometry window, turn on the color display just as you did before, by right clicking in the window and under Display Mode click Shot/Recv Elevations

Killing Traces Exit out of the geometry window to return to the Project Data List window. 1. Click the icon with three wiggles on it to display the seismic traces.

Right away, you can see a few bad traces. There could have been an issue with the geophone recording the trace.

Initially the data has no sort order. Let’s sort the data by shot.2. Click the sort order icon 3. Click shot order

Killing Traces 1. Click the Pick Data Trace Kills icon and a new list of icons appears.

2. In the Kill Trace toolbar, click the Pick Data Trace Kills icon

3. Click and drag in the rows displaying shot and channel number just above the traces to zoom in on traces. I have highlighted this area in red to help you see what I’m talking about.

Killing Traces 1. Once you are zoomed in, simply click the traces to kill them. A red line is now displayed instead of the traces you killed. 2. Zoom out by double clicking in the shot and channel row. I have highlighted this area in red to help you see what I’m talking about.

Note: you do not have to be zoomed in to kill traces. We’ve just found it is easier to select individual traces when you are zoomed in.

Note 2: If you kill a trace on accident just click the area where the trace was again to restore it.

Killing Traces – Sorting 1. By clicking the offset sort icon you can change between viewing the Traces in sequence or as offset from the source.

2. Scroll through all of the shots and kill all the bad traces you see.

3. When you are done, click the floppy disk and save all your picks to a kill trace file.

Killing TracesIt is important for you to understand what a bad trace looks like, and to get somewhat of a feel for how long the process takes. However, for the sake of consistency in processing this data set as a group we will upload a kill file that I have previously created.

1. Click the open file icon.

2. Select the .kil file you were given and click open

3. Save the kill picks to the Headers.

Defining LMO Function1. Click the Linear Moveout (LMO) Velocity edit icon

2. A new toolbar appears, Click the linear moveout velocity edit icon

3. Click to define the line of the LMO function, double click to end. You are picking along the first breaks. In this slide, you can see about where I picked my LMO Function in green.

Defining LMO Function

2. Click the Floppy Disk icon in the LMO Pick Toolbar, and save your LMO function. 3. Click Save

4. Click the M icon to return to the main seismic toolbar.

When you are happy with your choice, save it.

1. You can click the icon to display the linear moveout (LMO) function you have defined.

First Break Picking 1. Click the First Break Picking icon on the top of the seismic data screen.

Clicking the First Break Icon opens up a new set of icons from which to choose. Also, the display automatically changes to a shot offset sort. However, the data will already appear this way since we were just defining an LMO.

First Break Picking

1. Click the Auto pick current record icon. First break picks are display based upon the LMO function we just defined. The auto picks are now displayed on the seismic traces, but they’re black so you can’t really see them. Let’s change the color.

2. Click the on the First break pick toolbar.

3. Go to the Display tab. 4. Pick a bright color that displays well. 5. Click OK

Your first break picks will now be much easier to see.

First Break Picking1. If the picks look good on this shot record, then click the icon and autopick all the traces.

2. This will take a few minutes to load, but once it does you can scroll through shot records at the top right to check the fit.

Constructing a flowNote: Flows are integral to processing in Vista, and have many differences. Here we will construct a simple flow to crop the data.

1. Under Job Flow, select New Flow File 2. Return to the Job Flow menu, this time select Vista Flow Command Window

The Flow Command window provides a visualization list of all the options you have when creating a flow. You can drag and icon from the Flow Command Window to the Flow File Window in order to set up the flow.

Constructing a flow The majority of flows need an input and an output .

1. Click and drag an Input and an Output icon to the flow window.

2. Double click the input icon and set it [1] d_sg_stratton3d. Click OK

3. Right Click the input icon and click Data/Header SELECTIONS

Constructing a flow1. Click the Bin spreadsheet display icon to view data from a set of bins.

2. Click the green plus icon then enter the data as it appears in screenshot. 3. Click OK

4. Back in the flow file window, double click the output icon and change the name to something like crop1. Click OK

5. Click the flow link command icon . Then click and drag from the input icon to the output icon to link these commands.

Constructing a flow 1. Right click in the flow file window and select Set All Execute ON

2. The indicators on each icon will now be green. Click GO to run the flow.

3. The resulting traces look kind of ugly at first, but trying sorting them by different bin orders and you will see a better looking image!

Creating a 60Hz notch filter 1. Open a new flow file just as you did earlier.2. Open the Vista Flow Command Window too if it is not already open.

3. Drag and drop Input, AdjNotch, and Output to the flow command window.

8. Right click in the window and Set all to execute ON

9. Click GO

7. Draw arrows to connect the flows using the flow link icon

5. Double click the notch filter to change the parameters.

4. Set the original data file as the input

6. Name the output file 60Hz Notch

Note: 60Hz noise is commonly seen in seismic data. Why is this? It just so happens that power lines produce a signal at 60Hz.

Note: IF it appears the process is going to take a while to run, you can use your cropped data as the input to speed things up.

Notch comparison Left: A comparison of the original seismic data and 60Hz noise removed.

Right: A comparison of the CMP cropped data and 60Hz noise removed.

That’s all, hope you had a great time!