Beach Energy Ltd Lake Tanganyika 2D Transition Zone Seismic Survey Data Processing, 2014 Testing the Match between Vibroseis and Dynamite Data Reflection event timing and First-arrival timing Feb. 17, 2014

Vibroseis and Dynamite shot records were found on 2 stations using the same set of receiver stations on line BST14A-04 First, the relationship between reflections in the subsurface was analysed. As per theory, Vibroseis is recorded zero-phase positive and impulsive source (Dynamite) data is recorded minimum-phase negative. Therefore the Vibroseis data requires minimum-phasing and polarity reversal to match Dynamite data. Shot records are displayed for the station 1339 and 1473 as follows: Slides 5 and 8: Vibroseis as recorded from surface Slides 6 and 9: Dynamite shifted 6 msec to surface Slides 7 and 10: Vibroseis with minimum-phasing and reverse polarity applied After applying the minimum-phasing and reverse polarity to the Vibroseis data the reflection data timing is a perfect match with the Dynamite reflection data. Second, the relationship between the first-arrivals was verified since this is very important for data-ties using Refraction Statics. As shown on slides 11 and 12 the timing of first arrivals at various offset also matches very well after the above processes are applied to the Vibroseis data and both sets of first-arrivals are minimum-phase onsets to troughs.

Lake Tanganyika 2D Marine Seismic Survey Location of Lines

Shot Record Displays Sequence Input field data/Reformat Add Geometry: (from SPS files) Spherical Divergence Correction: (V**2)(T**1.2) Ensemble Balance: entire record scaled Low-cut: 4 Hz Squelch: noise reduction band, Vibroseis Hz Dynamite: Hz NMO correction: single brute function Trace Balance:.7 sec. windows Display: -ve = blue, +ve = red Note: impulsive source reflection data positive reflection co-eff. = -ve number or blue color

Vibroseis Shot Record, Station 1339, Line 04 from Surface

Dynamite Shot Record, Station 1339, Line 04 Shifted 6 msec to Surface

Vibroseis Shot Record, Station 1339, Line 04 from Surface, Minimum-phased, Reverse Polarity Vibroseis Reflection Data matches timing of Dynamite Reflection Data

Vibroseis Shot Record, Station 1473, Line 02 from Surface Vibroseis Shot Record, Station 1473, Line 04 from Surface

Dynamite Shot Record, Station 1473, Line 04 Shifted 6 msec to Surface

Vibroseis Shot Record, Station 1473, Line 04 from Surface, Minimum-phased, Reverse Polarity Vibroseis Reflection Data matches timing of Dynamite Reflection Data

Stack, Deep Zone - Line B67 (deep water) Tau-P Decon - 12 msec gap Applied 308 msec 391 msec After Minimum-phasing and Reversal of the Vibroseis Data First Arrival Timing Matches Between the Vibroseis and Dynamite Data Station 1339 VibroseisDynamite

Stack, Deep Zone - Line B67 (deep water) Tau-P Decon - 16 msec gap Applied 246 msec 427 msec After Minimum-phasing and Reversal of the Vibroseis Data First Arrival Timing Matches Between the Vibroseis and Dynamite Data Station 1473 VibroseisDynamite