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Recommended Practice onWell to Seismic Tie

Pamela Taeza

July 21, 2009

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Outline of the Presentation

I. Introduction and Objective

II. Well to seismic tie procedure

III. Helpful hints during well to seismic tie

IV. Summary

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Outline of the Presentation

I. Introduction and Objective

II. Well to seismic tie procedure

III. Recommended practice during well to seismic tie

IV. Summary

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Why is a good well tie important?

Align the synthetic trace computed from the well

log and link to the corresponding events of the

seismic section

More confidence on seismic interpretation

Impedance and inversion

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Impedance log not

correlated properly

Shift

Extract

Wavelet phase : time shift of logs

Shift the log

(change the depth-time

curve)

Extract the wavelet

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Theoretically, we can

shift the waveletinstead of the log

(1) If there is more

than one well, a

single wavelet shift

will not fix all the

mis-ties.

(2) Doing inversion

with the shifted

wavelet will

position the

derived impedance

at the wrong time.

Dont Shift

Extract

NOT DESIRABLE:

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(1) Use the well(s) and

seismic to extract both

the amplitude and phasespectra of the wavelet.

(2) Use the seismic alone to

extract the amplitude

spectrum of the wavelet.

Wavelet extraction

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Why not always use

the wells?

Log correlation

errors can cause

very big phaseproblems

Optimized log

correlation before

wavelet extractionusing wells

Extract

Extract

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Outline of the Presentation

I. Introduction and Objective

II. Well to seismic tie procedure

III. Helpful hints during well to seismic tie

IV. Summary

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Extract statistical wavelet

Current correlation: -0.316

Max. correlation: 0.374 at -44ms time shift 10

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Select best match eventsand bulk time shift

Current correlation: -0.316

Max. correlation: 0.374 at -44ms time shift 11

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Select best match eventsand bulk time shift

Max. correlation: 0.354 at 8ms time shift

Current correlation: 0.062

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Stretch-squeeze

2

1

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Apply relative changes Change depth-time curve only

QC sonic log velocity changes

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Current correlation: 0.545 using statistical wavelet

Max. correlation: 0.545 at 0ms time shift 15

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Rotating wavelet phase

Phase rotation: -111 deg16

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Extract wavelet using well

Current correlation: -0.166

Max. correlation: 0.711 at -6ms time shift

Phase: -110 deg.

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Correlation: 0.713 using wavelet from well 8-08

Max. correlation: 0.713 at 0ms time shift18

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Outline of the Presentation

I. Introduction and Objective

II. Well to seismic tie procedure

III. Helpful hints during well to seismic tie

IV. Summary

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Helpful hint 1:

Create an interval velocityout of the depth-time

correlated P-wave

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QC sonic log velocity changes

Interval velocity 21

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Too much stretch-squeeze!

Interval velocity 22

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Helpful hint 2:

Compare wavelet phase and shape from wells

16-08

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Helpful hint 3: Base Map

Create an arbitrary line containing all wells

BASE MAP

16-08

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Extract global wavelet

Current correlation: 0.661 using wells

Ave. wavelet phase: -56 deg. 25

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Helpful hint 4:

Compare DT of wells 26

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DT of 4 wells

16-08

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1.Structural complexity

2.Rapid lateral variations in velocity and reflectivity

3.Unconformable dips within the match gate

4.Finely layered sequences having severe

impedance fluctuations

Geologic factors that canstand in the way of a good tie:

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Outline of the Presentation

I. Introduction and Objective

II. Well to seismic tie procedure

III. Helpful hints during well to seismic tie

IV. Summary

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Summary

1.Extract statistical wavelet and do log correlation

before extracting wavelet from wells

2.Extract the average wavelet from multi-wells to fine

tune log correlation

3.Create an Interval velocity from the Depth-timePwave correlated

4.Compare wavelet phase and shape of all wells

5.Create an arbitrary line from all the wells6.Compare DT of all wells

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Questions?