BP AIT 2004 2D velocity benchmarkFrederic Billette – AIT Houston

Copyright s BP America Inc. - No release, transfer, license, sell, trade or otherwise disclosure permitted outside of Queen’s U.

Legal issuesData release agreement dated February 3rd, 2004 and

confidentialityagreement dated September17th, 2004 specify that:

• You can:– use the dataset internally for any purpose.

– Publish / show results using this dataset.

– Show these slides internally.

– Publish / show your result compared to the exact model after specific permission to be obtained from BP (billetfj@bp.com).

• You can not:– Release, distribute or sell the dataset.

– Show, release, distribute or sell any material extracted form this presentation to a third party (exception specified above).

Agenda

• Model, data, challenges, …

• Queen’s U. contribution

• Velocity model comparison

• PSDM image comparison

• Feedback & ranking

Timeline

Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

2003 2004

Model generation

Data generation

QC

Data offered tothe industry

Exact model revealedResults collected

Resultsanalyzed

Feedback to contractors

Feedbackprovided

Results distributed to the network

Model Generation

Velocity

Density

67km wide, 12km deep, build on a 6.25m x 6.25m grid

Salt 1 - Shot migration no SRME

overpressurezones

sedimentinclusion

complexoverhangs

Complex/brokenreflectivity

Challenges 1/3

rugose top salt

multiples

steepdips

Salt 2 - Shot migration no SRME

poorly imagedflanks

shallow HVanomaly

channels

Challenges 2/3

Extra salt - Shot migration with SRME

HV anomalies onstructure flanks

shallow LV anomalies

mud volcano

shallow gas

Challenges 3/3

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.

Data transfer

• Tape or ftp download available.

• Document with experiment details provided.

• 15km of offset..

• Model to be returned by June 9, 2004 when the exact model was revealed.

Data recipients

• 1 oil company

• 13 seismic contractors

• 7 universities

• 3 research institutes

• 1 software company

Total: 25

Presented results publicly at the EAGE

• 0 oil company

• 5 seismic contractors: CGG, Veritas, GXT, Paradigm, and Data Modeling Inc. (Calgary)

• 2 universities: KACST (Riyadh) and Queen’s (Kingston)

• 2 research institutes: SINTEF (Trondheim) and OPERA (France).

• 0 software company..

Total: 9

Participating to BP benchmark

• 0 oil company

• 8 seismic contractors: CGG, Veritas, WesternGeco, PGS, GXT, Fairfield, Paradigm, Data Modeling Inc. (Calgary)

• 2 universities: DIG (Paris), Queen’s (Kingston)

• 2 research institutes: SINTEF (Trondheim) and OPERA (Pau)

• 0 software company..

Total: 12

Queen’s University contributors

Small team work in an university lab

Professor:

Gerhard Pratt

Student:

Drew Brenders

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

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)

Exact model

Exact model: velocity contours

Queen’s University

A

B

C

Note: C did not deliver the right part of the model on time.

C

Note: C delivered the right part of the model on September 1st, 2004.

D

E

Note: E estimated the model extra-salt only

F

Note: left and right part have been updated independently.

H

I

J

Note: J estimated the sediment velocities only

K

L

Note: L estimated the model extra-salt only

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.

Exact density model

Exact model

Exact model

Queen’s University

A

B

C

Note: C delivered the right part of the model on September 1st, 2004.

D

E

Note: E estimated the model extra-salt only

F

Note: left and right part have been updated independently.

H

I

J

Note: J estimated the sediment velocities only

K

L

Note: E estimated the model extra-salt only

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.

+

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.

-

Ranking Process

• Ranking along 2 axes: 1) salt & sub-salt ; 2) extra salt sediment

update.

• Ranking is an average after ~12 peer review.

• Only results provided on time were considered.

• Ranking is based on this test only.

Ranking

B

IA

K

J

E

L

Quality of salt and sub-salt model building

Acc

ura

cy o

f extr

a-s

alt

sedim

ent

update

F

H

C

D

Ranking

IA

K

J

E

L

Quality of salt and sub-salt model building

Acc

ura

cy o

f extr

a-s

alt

sedim

ent

update

F

Tier 1Tier 2Tier 3

Tier 1

Tier 2

Tier 3

H B

C

D

Questions?