1. Beach Energy Ltd
Lake Tanganyika 2D Marine Seismic Survey
Data Processing, 2014
Revised Displays
Tau-P Domain Linear Noise Attenuation Tests
Lines BST14B24 and BST14B67
Revised Feb. 25, 2015

2. Notes on Revisions:
Tau-P transform was originally performed using a bandwidth of 2 to 125 Hz.
The data contains water-borne dispersive and direct arrival noise up to 200 Hz
(data beneath water-bottom may contain useable frequencies up to 90Hz in the
shallow)
Therefore stacks and difference plots required a Hz to equalize to
the transformed data in order not to show differences along the water bottom and
shallow areas. The image at the water bottom will also improve greatly with improved
stacking mute design.
A Bandpass filter was applied to the data before shot record, stack and difference
plot displays were generated, to remove the data differences not inherent in the
Tau-P linear noise attenuation process.

3. Linear Noise can be removed in the Tau-P domain using a mute defined
by slowness or velocity.
For testing, shot records and stacks were viewed before and after the application
of Tau-P Domain Linear Noise Attenuation. Line BST14B24 was used as an
example of data from a shallow water area and Line BST14B67 was used as an
example of data from a deep water area.
The design of the Tau-P mute is fairly "mild" to ensure preservation of dipping
reflection data on the shot records and this process should not be applied
in the areas where the water bottom dip is very steep. Each line will have to be
QC'd for site specific application.
The application of Tau-P Linear Noise Attenuation is recommended.

4. Tau-P Linear Transform Parameters
Type: Hi res Radon
Min Frequency: 2 Hz
Max Frequency: 125 Hz
Max. Offset : 3100 m
Min Slowness: -0.7 msec/m
Max Slowness: 1.2 msec/m

5. Lake Tanganyika 2D Marine Seismic Survey
Location of Test Lines

6. Shot Record Displays Sequence Input field data/Reformat
Add Geometry: (theoretical straight line)
Spherical Divergence Correction: (V**2)(T**1.6)
Ensemble Balance: entire record scaled
Low-cut: 4 Hz
Squelch: noise reduction band, Hz
FXSwell: noise freq. Range: 3-30 Hz
Tau-P Domain Linear Noise Attenuation: Hi-res, Hz, muted
BandPass Filter: Hz (before differencing)
Display: -ve = blue, +ve = red
Note: impulsive source reflection data
positive reflection co-eff. = -ve number or blue color

7. Shot Gather 1208, Line B24 (shallow water)
Before Tau-P Linear Noise Attenuation Applied

8. Shot Gather 1208, Line B24(shallow water)
After Tau-P Linear Noise Attenuation Applied

9. Shot Gather 1208, Line B24 (shallow water)
Difference After Tau-P Linear Noise Attenuation Applied

10. Shot Gather 1208, Deep Zone, Line B24 (shallow water)
Before Tau-P Linear Noise Attenuation Applied

11. Shot Gather 1208, Deep Zone, Line B24(shallow water)
After Tau-P Linear Noise Attenuation Applied

12. Shot Gather 1208, Deep Zone, Line B24 (shallow water)
Difference After Tau-P Linear Noise Attenuation Applied

13. Tau-p Domain Display , Line B24 (shallow water)

14. Tau-p Domain Display , Line B24 (shallow water)
with Mute applied

15. Tau-P Transform Only
Forward/Reverse/Difference
Shot Record Displays

16. Input Shot Gather 1208, Line B24 (shallow water)

17. After Forward/Reverse Tau-p Transform

18. Difference After Forward/Reverse Tau-p Transform

19. Stack Displays Sequence Input field data/Reformat
Add Geometry: (theoretical straight line)
Spherical Divergence Correction: (V**2)(T**1.6)
Ensemble Balance: entire record scaled
Low-cut: 4 Hz
Squelch: noise reduction band, Hz
FXSwell: noise freq. Range: 3-30 Hz
Tau-P Domain Linear Noise Attenuation: Hi-res, Hz, muted
Bandpass Filter: Hz
NMO correction: preliminary velocities
Stack
High-cut: 83 Hz
Trace Balance: .7 sec. windows
Display: -ve = blue, +ve = red
Note: impulsive source reflection data
positive reflection co-eff. = -ve number or blue color

20. Stack, Line B24 (shallow water)
No Tau-P Linear Noise Attenuation Applied

21. Stack, Line B24 (shallow water) Tau-P Linear Noise Attenuation Applied

22. Stack, Deep Zone, Line B24 (shallow water)
No Tau-P Linear Noise Attenuation Applied

23. Stack, Deep Zone, Line B24 (shallow water)
Tau-P Linear Noise Attenuation Applied