Post on 02-Jun-2018
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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?