1. BP AIT 2004 2D velocity benchmark Frederic Billette – AIT Houston Copyright s BP America Inc. - No release, transfer, license, sell, trade or otherwise disclosure permitted outside of Queen’s U.

2. Agenda Model, data, challenges, … Queen’s U. contribution Velocity model comparison PSDM image comparison Feedback & ranking

3. Timeline Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep 20032004 Model generation Data generation QC Data offered to the industry Exact model revealed Results collected Results analyzed Feedback to contractors Feedback provided Results distributed to the network

4. Model Generation Velocity Density 67km wide, 12km deep, build on a 6.25m x 6.25m grid

5. Salt 1 - Shot migration no SRME overpressure zones sediment inclusion complex overhangs Complex/broken reflectivity Challenges 1/3 rugose top salt

6. multiples steep dips Salt 2 - Shot migration no SRME poorly imaged flanks shallow HV anomaly channels Challenges 2/3

7. Extra salt - Shot migration with SRME HV anomalies on structure flanks shallow LV anomalies mud volcano shallow gas Challenges 3/3

8. Data generation 2D Finite difference acoustic modeling (variable velocity & density). Free-surface multiples are present. Data shot split-spread (streamer data provided), every surface point recording data. Shot every 50m, receiver every 12.5m. 6ms sampling. Frequency peak is 27Hz and data can be whitened up to 54Hz. The wavelength is causal and has not been 0 phased (see typical trace below), time delay can be estimated considering the zero offset traces.

9. Participating to BP benchmark

10. Queen’s University contributors Small team work in an university lab Professor: Gerhard Pratt Student: Drew Brenders

11. Queen’s U. processing flow Reduced the dataset: 1 - 7.5Hz, 1/8 shots and 1/8 receivers, 2km – 15km offset Initial smooth model using first-arrival travel time tomography Automatic velocity update without migration using waveform tomography No salt interpretation, all automatic Did not request feedback

12. Part1: velocity models Display information All images are vertically exaggerated 3 times DX=25m ; Dz=6.25m Images are 67km wide and 12 km deep Velocity scale goes from 1429m/s to 4790m/s (min & max in the exact model)

13. Exact model

14. Exact model: velocity contours

15. Queen’s University

16. Part2: migrations Display information All images are vertically exaggerated 3 times DX=25m ; Dz=6.25m Images are 67km wide and 12 km deep Model have been expanded or reduced if necessary 2D SRME has been applied No other pre or post-processing applied 2D wave-equation migration (downwards propagation only) For display purposes, low frequency outputs are presented Exact water layer has been inserted.

17. Exact density model

18. Exact model

20. Queen’s University

21. Queen’s University: strengths Good long & short wavelength updates in the shallow section. Impressive resolution for some shallow anomalies. Good image of the top salt without interpretation. Good delineation of the overhangs without interpretation. See glimpses of the base salt. +

22. Queen’s University : weaknesses Deep part of the model not estimated. Variable velocity in salt. Too high frequency. Regularization/smoothing issues? Imaging issues with several targets, even shallow. -

23. Ranking I A K J E L Quality of salt and sub-salt model building Accuracy of extra-salt sediment update F Tier 1Tier 2Tier 3 Tier 1 Tier 2 Tier 3 H B C D

24. Questions?