The computation of near surface corrections for seismic processing of data in the Taranaki Basin - recent experience

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The computation of near surface corrections for
seismic processing of data in the Taranaki Basin
- recent experience Nigel Fisher Kenmore
Geophysical
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Typical Land Processing Sequence
Amplitude Recovery
Deconvolution
(Refraction) Statics
Velocity Analysis
Residual Statics
Normal Move-out
Muting
Stack
Migration
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Typical Land Processing Sequence (with suggested
relative importance)
Amplitude Recovery
Deconvolution
Refraction Statics
Velocity Analysis
Residual Statics
Normal Move-out
Muting
Stack
Migration
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Elevation
-100 m
Base of weathering
0 m
elevation profile
Line A elevation profile and base of weathering
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Elevation
-200 m
Base of weathering
-100 m
elevation profile
Line B elevation profile and base of weathering
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Weathering static

dt delay time
vw weathering velocity
vr refractor velocity
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Elevation
-100 m
Base of weathering
0 m
elevation profile
Line A elevation profile and base of weathering
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Elevation
-100 m
0 m
elevation profile
Line A weathering static applied
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-100 m
0 m
elevation profile
Line A weathering static datuming
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just another inverse problem
A x b
Matrix or other operator
Observations
Unknowns

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and for refraction computation
A x b
Delay Time Refractor Velocity
First Arrivals

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Sample shot showing picked first breaks
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Pick all first breaks

Refraction Computation
Refractor Velocity
Delay Time

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Weathering static

dt delay time
?
vw weathering velocity
vr refractor velocity
?
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application of delay time to shot records
should align first break energy
so can QC delay time results

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Shot showing picked first breaks
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Shot showing picked first breaks delay time
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Successive shots linear move-out
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Successive shots linear move-out delay time
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Delay time profiles, lines A (top) and B
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Weathering static

dt delay time
?
vw weathering velocity
?
vr refractor velocity
?
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possibilities for estimating vw
(i) dynamite source, vw depth/tuh
(ii) estimate vw from near offsets
(iii) choose representative constant vw
(iv) deep uphole survey - provides static
control and sparse estimate of vw


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Reprocessed 2003

Differing structure due to how the deep upholes
are used

Original processing
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Reprocessed 2003

E
Differing structure due to how the deep upholes
are used
W

Original processing
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... some lines may remain problematic