Seismic Studio Tutorial - Part 4Stack QC

Boulder, Colorado USANovember, 2004

OverviewStack slice QC generates arbitrary 2D lines, called slices from your 3D prospect. You specify the CMP spacing and grab radius for each line. Traces can therefore be multiply assigned to CMPs. This can take some time.You pick a velocity field using semblance analysis for each stack. This velocity field is throw-away; it does not get exported.You create stacks and can look at any two stacks from the current slice.The traces you stack are the actual un-decond data you use for your refraction picking.

Stack QC WindowAccessed under Stacks on the Menu BarThe Stack Slice window provides a wide range of functionality: Slice selection along any arbitrary line Semblance velocity analysis Stack with and without staticsAzimuthal limitation

Stack Slice WindowWorks from slices you select from your data

Is map-drivenDrag a line on the map to create a sliceSet a CMP spacing and capture radiusCreates a 2D SEG-Y file for each sliceSlice ManagerDelete old slicesSelect current slice from list

Control Pane 2This contains the map and map controlsControl Pane 1You drive the window from hereTrace and Semblance Display PaneThis is where you see everything

Control Pane 1Stack display provides control over stack trace display parameters: wiggle, fill color, trace excursion, etc.Stack filter for applying simple bandpass filter and some gain optionsSalience experimental lets not go thereAuto picker experimental we are developing some automatic velocity picking functionalityAzimuth for azimuthally limiting traces in the semblance analysis and in the stack. Semblance/Mute for setting min/max velocities in the semblance and the stretch mute percentage

(** Bold italics indicate important, often used tabs.)

Control Pane 1Slice Manager this is where you select which slice you want to work onStatics for applying static correctionsGather filter for applying a bandpass filter and gain optionsStack manager this is where you actually name your stacks and generate themGather display provides control over stack trace display parameters: wiggle, fill color, trace excursion, etc.

Change map to any value in databaseResize bars click and drag

Here we have gone to the Slice manager and see a slice we created back in Feb, 2004. We have pulled up the resize bar to make the base map bigger. The black line shows the existing slice.

To create a new slice simply click and drag a line across the map.

You will see this dialog for creating a new 2D SEGY file. Then you see this information dialog.

This dialog comes up. There are two passes. The first pass counts. Then space is allocated. The second pass creates the actual SEG-Y file. The second pass can take a while for long lines with wide trace radii.

Select the line in the Slice manager, the line is highlighted in red on the map.Click on these navigation buttons to move into the line.

Once you see a CMP gather you like, you can pick velocities.As you move your mouse across the gather, the green line on the base map indicates the shot/receiver line for each trace.

Left click to set velocity points.Click D to delete the closest point to the mouse.

Click on Velocity display and push the Recompute velocity field from knees button.

Now you can drive the velocity analysis from this display. Left-click where you want to pick a new velocity point.

Go back to the Velocity display and click the Recompute button again.

Break timeSo, at this point we have:Created a sliceComputed a velocity field.

But our data have no statics applied, we will do that later. First, lets create a stack with no statics applied.

First, resize Control Pane 1 so you can see more controls. Second, click on the Stack manager tab

1. Type in the name for your stack. 2. Type in the maximum time for your stack. The default is 1000 msec. 3. Click on Create new stack button

To see your stack, click on the View two stacks tab.Then click on the stack name in the drop down list, and click Load.

Applying staticsNow we will create a stack with statics applied.

Click on the Statics tabClick on the Apply statics from the selected header radio button. The default header location is Static Correction which is where your current refraction statics are stored.

Recompute stacking velocitiesNow you should repick your velocities, because they after refraction statics are applied they will change.

We recommend repicking the velocities at the previous locations.The best way to do this is to zoom in (right mouse button) on a previous location then left click.Click carefully on one of the dots

This one doesnt need much change.

This one should be changed, especially under 700 msec.

Recompute the velocity field

Create a new stack dont forget to name it

Now you have two stacks and they zoom together.

ConclusionsSlice stack QC is for checking the quality of your statics solution.You can create as many stacks as you want. The window only keeps one velocity field at a time. You cannot save a velocity field to retrieve it later.You cannot export a velocity field to another processing system.