4 This is a base map of your bin fold coverage If you want to show sources and detectors on the map, check these then “Reload plot.”This is a base map of your bin fold coverage
5 Click on base map to see picks centered on the closest bin Here are the picks centered on the base map positionplotted by offset vs time
6 Currently we are assigning picks to the first refractor By dragging the line you have done 3 things:You have set a first refractor offset rangeYou have estimated a refractor velocityYou have estimated a delay timeTo set refractor branch information drag a best-fit line over the range of picks you want to assign to the first refractor
7 These values are provided here and can be edited The zero offset intercept estimates 2x the delay timeThe slope of the line estimates the refractor velocityRefractor offset distance is shown by the red zone
8 Another way to use the Branch Assignment window As before the offsets, velocity and delay time appear here and are editableClick on “Apply LMO correction to picksNow move the sliderDrag the line again to specify the offset range for First refractorAnother way to use the Branch Assignment window
9 The base map provides a map of the branch parameters To accept all these branch assignment parameters, you must push “OK – apply changes” button
10 After accepting your new branch assignment field, you will be asked if you want to interpolate the delay times and velocities to the source and detectorsIf you push “Yes,” this will initialize the source and detector databases with these delay times and refractor velocities. If you already have a refractor solution from previous session, these new values will replace the old solution.You will have one more chance to change your mind.
11 If you said “Yes” to interpolating the delay times and velocities to the source and detector tables, you will next see this “process” window.
12 Applying analyses to traces Next, you will see how to apply a delay-time and refractor-velocity solution to the tracesThe following two slides show the program options that you can use to help QC delay time and refractor velocities
13 From a conventional pick window … Push the “M” toggle buttonUnder Options/Display under “Background color options,”Click on “Use the branch numbers (if assigned)”
14 Eliminate the traces that don’t belong to the refractor – Push ‘X’ toggle button Push “T” toggle button to limit the time window
15 Applying the branch assignment derived delay times and refractor velocities Recall that above we assigned branch offsets in the Branch Assignment windowRecall that by assigning branch offsets, we also determined a crude delay time field and a refractor velocity fieldNow we will apply those fields to our traces, using the technique we just describedNote that we have also turned off the refractor background color to simplify the display
16 A perfect refraction solution (refractor velocities and delay times) would flatten the refractor to zero time.This shot is pretty good, meaning the refractor velocity and delay times for this source and its detectors are probably close to correct
17 This source did not respond as well This source did not respond as well. The simple delay times interpolated from the branch assignment are not correct in detail.This does not mean that this source has a problem. It just means that the delay time and refractor velocity field are not accurate for this location.The flatness should improve when we actually compute refractor velocities and delay times from the picks themselves … in the next step.
18 Let’s see how the delay-time and velocity solution we picked in branch assignment looks in another window.
19 Inline-crossline azimuth-limited common-offset pick window We will look at the solution applied to the traces that fall within a narrow offset range and a narrow azimuth rangeWe will look at these limited traces across an entire prospect
20 This cross line shows significant residual shape. Here is the common-offset window with the branch-derived velocity and delay times applied.As with the source record display, flattened traces imply a good solution.In general, refracted arrivals along this inline and crossline line up pretty well on zero.This cross line shows significant residual shape.
21 Click on RVC for a conventional least-squares solution Compute conventional refractor velocities and delay times by going to Model/RVC delay time/velocity computation sequence
22 This runs your data through a standard sequence of steps shown here
23 Analysis QC At this point You have picked refracted arrivals You have assigned your picks to refractorsYou have computed refractor velocities and delay timesYou have also estimated source and detector geometry errorsThis is automatically performed as part of the standard sequenceIt estimates source and detector mispositions
24 At this point in the tutorial you will examine your velocity and delay time fields
25 Click on Model/3D (and 2D) model building window
26 In this window, the surface elevations, weathering velocity and weathering thickness are accessed through “weathering layer”
27 Refractor delay times, refractor velocities and elevation of the refractors are accessed via “First refractor,” “Second refractor,” etc.Note: Some versions of Seismic Studio require you to click on “Weathering layer definition” before you can examine refractor parameters
28 This window can be used to construct simple refractor-based earth models.
29 In this case, we will use the default constant weathering velocity of 2000.
30 The result is this “First refractor elevation” surface. To smooth the refractor elevations (and cause the weathering velocity to be modified) click on “Modify attribute”Note: Modify attribute will modify the attribute that is currently being displayed.
32 To compute statics, click here The weathering velocity is no longer constant 2000.This now displays the smoothed first refractor elevation.If you change your mind, you can undo the modification here.
33 Statics in Seismic Studio Seismic Studio computes an individual static value at each source and detector location.Statics are calculated as the sum of vertical times through each model layer, then to an intermediate datum, then to a final datum.Both the intermediate datum and final datum are optional.
34 Statics in Seismic Studio SurfaceWeathering velocity … set in model building, typically varies spatiallyRefractorRefractor velocity …varies spatiallyIntermediateDatumReplacement velocity … constant, user-specifiedFinalDatumFor this model, at any station location,the static will be the sum of 3 times.
35 Statics in Seismic Studio SurfaceT1T1 = layer-thickness / weathering-velocityT2T2 = refractor-to-intermediate datum thickness / refractor-velocityT3T3 = intermediate-to-final datum thickness / replacement-velocityFor this model, at any station location,the static will be the sum of 3 times.
36 Statics in Seismic Studio SurfaceAs mentioned above, both the intermediate datum and final datum are optionalT1T1 = layer-thickness / weathering-velocityT2T2 = refractor-to-final datum thickness / replacement-velocityIf no intermediate datum is requested, for example, then the static would be the sum of two times
37 Accessing the Statics Wizard Each of Seismic Studio’s model building windows has a “Compute statics” button.
38 This is the first page of the Statics Wizard If you want either an intermediate datum or a final datum, check them here.Click “Next >>”
39 If you requested an intermediate datum, you design it here The wizard shows you some model statistics to help youFor this model, we choose an flat intermediate datum of -100 to be just beneath the refractorClick “Next >>”
40 If you requested an final datum, you design it here Again, the wizard shows you some model statistics to help youFinal datum elevation and replacement velocity are often specified by the project clientClick “Next >>”
41 Otherwise, you can ignore this page. If your data have uphole information associated, then this page provides several options.Otherwise, you can ignore this page.Click “Finish”
42 In the “3D (and 2D) model building window,” click “Plot statics” to see the statics you just computed.
43 What to do with the statics You can see some stacks of the traces with statics appliedYou can export the statics for use by other processing systems
44 To Stack traces in Seismic Studio click on “Stacks”
45 Slice Stacking in Seimic Studio Will be presented in a special tutorial
46 Exporting staticsStatics are computed for each source and detector in the surveyThere are several options for exporting the statics for use by processing systemsThis tutorial will show you one option:Export source/detector tables
56 ConclusionsThis tutorial shows you a standard analysis/modeling path through Seismic StudioOn simple data, this may be an adequate templateFor more difficult data, more advanced procedures may be requiredAdvanced procedures can be learned via a Renegade training class