Refraction Statics

Bryce HutchinsonSumit Verma

3D Statics display

1. Click this button on the right side of the statics window to open a 3D statics display

2. Right click in the window that opens. Under 3D Display View, click Statics View

3. This display shows the static shift, in milliseconds, for individual shots and receivers throughout the survey. Click and hold to rotate the image and scroll to zoom in or out.

how much correction will be applied to the source and receiver!

Refraction Statics1. Return to the refraction statics window by clicking the icon next to your primary dataset

2. Click to the “O” for options at the top left of the window

3. Change the refraction replacement velocity to 5500

4. Click over to the shot info tab. Be sure that Surface Source is selected since our source is a Vibroseis truck. Click OK

5. Click Ss and Rs to calculate the shortwave and refraction statics.

1. Save your static results to a text file.

2. Close the window

4. Change the name of the sort and the main and secondary sort keys

3. Click the green plus next to Sort Data Tools at the bottom of the Project Data Sets window

Statics Flow

1. Now we will create a statics flow. I’ll run through the settings for each flow command.

2. Set the input to the raw data

3. In the sort tab, change it to the sort we just created

Statics Flow

4. Save your statics file output and throw your name on there like Sumit! Click GO to run the flow.

1. In the ReadStatics flow command, Click File and choose the text file that we saved earlier in the refraction window. 2. Be sure the Source and Receiver Static Headers are set as above.

3. In StatShft, set the Vista Defined Header Static as Static_Total. It should default as this.

Notice here we have not calculated elevation statics. So, currently total statics is refraction statics!

NMO Flow

1. Set It is time to create a normal moveout (NMO) flow

2. Set as the input the static file we just created

3. Define the sort as CMP_NO

4. Read in the velocity file that you created in the semblance window. It should be the only option. 5. Apply an NMO Stretch Mute

6. Name your output! Click GO to run the flow

1. Run the flow again, but this time use the raw data as the input. Keep everything else the same.

Next we will stack each of these datasets we just created.

CMP Stack

3. Right click Input and Data/Headers Selection

4. Click the 3D icon then the Green plus. Then match the Inline and Crossline values to those below.

1. Set the input as the NMO Static applied data

2. Set sort to CMP_NO

5. CMP Stack settings should appear as such by default

CMP Stack

1. Don’t forget to save your output file! 2. Repeat the same simple stack flow for the raw dataset with NMO applied to it.

When you finish, you will have two stacked datasets. Both stacks will have NMO performed on them, but one will have statics applied and one will not. You can see our comparison on the next two slides.

Compare the data before and after statics applied!

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NMO Stack – no statics

2-13

NMO Stack – statics applied

Points to note!• You can test for different refraction velocity and see how does it affect your (Compare before and after refraction statics applied!)

– Shot gather – NMO corrected Gather – Stacked data set After refraction statics, we expect the reflectors to be better flattened on the NMO gather .

Here, refraction statics does not show much effect, and probably you can find a better refraction velocity by trial and error.

• Refraction statics and elevation statics are some of those processing steps on which, you must take advice from an experienced processer.

Raw- no NMO

We expect you to know how to generate these images!!Ask for help if you can not!

Statics applied no NMO

Raw – with NMO

Statics applied with NMO