Transcript Seismic Attribute Sensitivity to Energy, Bandwidth, Phase, and Thickness Greg A. Partyka

Seismic Attribute Sensitivity to
Energy, Bandwidth, Phase, and
Thickness
Greg A. Partyka
BPAmoco
Two Goals
1 Review common attributes.
2 Summarize attribute sensitivity
– to energy, bandwidth, and phase; via simple halfspace models.
– to thickness; via simple wedge models.
Model Descriptions
7 half-space models
– Laterally consistent reflectivity
– Laterally variable wavelet properties
Statics, variable source & receiver coupling, and attenuation are
three main causes for laterally variable wavelet properties.
3 wedge models
– Laterally consistent wavelet properties.
– Laterally variable reflectivity.
Lithology, fluid, and thickness are three main causes for laterally
variable reflectivity.
energy
(amplitude)
Energy Model
1.8
1.6
1.4
1.2
1.0
100
travel-time (ms)
0
bandwidth
(Hz)
Bandwidth Model
8-10-44-54
8-10-38-48
8-10-32-42
8-10-26-36
8-10-20-30
100
travel-time (ms)
0
phase
(degrees)
Phase Model
240
180
120
60
0
100
travel-time (ms)
0
bandwidth
(Hz)
energy
(amplitude)
Energy-Bandwidth Model
1.8
1.6
1.4
1.2
1.0
8-10-44-54
8-10-38-48
8-10-32-42
8-10-26-36
8-10-20-30
100
travel-time (ms)
0
phase
(degrees)
energy
(amplitude)
Energy-Phase Model
1.8
1.6
1.4
1.2
1.0
240
180
120
60
0
100
travel-time (ms)
0
phase
(degrees)
bandwidth
(Hz)
Bandwidth-Phase Model
8-10-44-54
8-10-38-48
8-10-32-42
8-10-26-36
8-10-20-30
240
180
120
60
0
100
travel-time (ms)
0
phase
(degrees)
bandwidth
(Hz)
energy
(amplitude)
Energy-Bandwidth-Phase Model
1.8
1.6
1.4
1.2
1.0
8-10-44-54
8-10-38-48
8-10-32-42
8-10-26-36
8-10-20-30
240
180
120
60
0
100
travel-time (ms)
0
Real Amplitude - Sensitivity
0
100
0
100
0
100
100
0
100
0
100
0
100
travel-time (ms)
0
Reflectivity Wedge Models
Blocky Wedge
100
200
Blocky/Gradational Wedge
100
200
Gradational Wedge
100
200
travel-time (ms)
0
travel-time (ms)
0
travel-time (ms)
0
reflection
coefficients
1.0
-1.0
0.1
Real Amplitude
Blocky Wedge
100
200
UNRESOLVED
Blocky/Gradational Wedge
RESOLVED
100
200
Gradational Wedge
100
200
travel-time (ms)
0
travel-time (ms)
0
travel-time (ms)
0
8-10-40-50hz
Ormsby filter
Two Classes of Attributes
• Instantaneous Attributes
• Response Attributes
Instantaneous Attributes
• Characterize sample-by-sample variability.
• Include:
– real amplitude,
– quadrature amplitude,
– reflection strength,
– instantaneous phase,
– cosine of the instantaneous phase,
– instantaneous frequency.
Quadrature Amplitude
Real Amplitude
Quadrature Amplitude
• 90 degree phase rotation (or Hilbert transform).
• Zero-Crossings
Peaks & Troughs.
• Also called “the imaginery part of the seismic trace”.
Quadrature Amplitude - Sensitivity
0
100
0
100
0
100
100
0
travel-time (ms)
0
100
0
100
0
100
sensitive to:
• energy
• bandwidth
• phase
Quadrature Amplitude
Blocky Wedge
0
100
...zero-crossings can represent bed boundaries,
much like bandlimited acoustic impedance.
Blocky/Gradational Wedge
200
100
200
Gradational Wedge
100
200
travel-time (ms)
0
travel-time (ms)
0
travel-time (ms)
If input data is zero-phase...
Reflection Strength
Real Amplitude
Quadrature Amplitude
Reflection Strength
• Phase independent.
• Always greater-than or equal-to zero.
• Also referred to as “energy envelope”.
Reflection Strength - Sensitivity
0
100
energy
2
0
100
0
0
100
100
0
travel-time (ms)
0
100
0
100
0
100
sensitive to:
• energy
• bandwidth
Reflection Strength
Blocky Wedge
100
Exposes classic tuning behaviour.
Blocky/Gradational Wedge
200
Lateral variations indicate changes
in acoustic contrast and bed thickness.
Gradational Wedge
200
0
100
200
2
travel-time (ms)
100
0
travel-time (ms)
0
travel-time (ms)
0
energy
2
0.7
0
0
Instantaneous Phase
Real Amplitude
Quadrature Amplitude
Instantaneous Phase
Instantaneous Phase
• Strong and weak events exhibit equal strength.
• Discontinuous at trough locations (+/-180 degrees).
• Commonly displayed with a wrapped color bar.
180
0
-180
Instantaneous Phase - Sensitivity
0
100
0
phase
(degrees)
180
100
0
0
100
100
0
travel-time (ms)
0
-180
100
0
100
0
100
sensitive to:
• bandwidth
• phase
Instantaneous Phase
Blocky Wedge
100
200
Emphasizes reflection continuity/discontinuity.
Blocky/Gradational Wedge
phase
(degrees)
180
0
-180
200
Strong and weak events exhibit equal strength.
100
200
travel-time (ms)
0
travel-time (ms)
0
100
Gradational Wedge
travel-time (ms)
0
highlights:
faults
pinch-outs
angularities
boundaries
onlap/offlap
Cosine of Instantaneous Phase
Real Amplitude
Quadrature Amplitude
Instantaneous Phase
Cosine of
Instantaneous Phase
• Like instantaneous phase, but
• Avoids the +/-180 degree discontinuity that plagues phase.
• Can therefore be further processed.
Cosine of Instantaneous Phase - Sensitivity
0
100
0
amplitude
1
100
0
0
100
100
0
travel-time (ms)
0
-1
100
0
100
0
100
sensitive to:
• bandwidth
• phase
Cosine of Instantaneous Phase
Blocky Wedge
100
200
Emphasizes reflection continuity/discontinuity.
Blocky/Gradational Wedge
0
Strong and weak events exhibit equal strength.
100
200
travel-time (ms)
0
travel-time (ms)
0
200
Peaks and troughs retain their positions.
amplitude
1
-1
100
Gradational Wedge
travel-time (ms)
0
highlights:
faults
pinch-outs
angularities
boundaries
onlap/offlap
Instantaneous Frequency
Real Amplitude
Quadrature Amplitude
Instantaneous Phase
Instantaneous Frequency
• Rate of change of instantaneous phase.
• A measure of time-dependent mean frequency.
Instantaneous Frequency - Sensitivity
0
100
0
frequency
(Hz)
25
100
0
100
100
0
travel-time (ms)
0
10
100
0
100
0
100
sensitive to:
• bandwidth
Instantaneous Frequency
Blocky Wedge
100
200
Emphasizes tuning characteristics.
Blocky/Gradational Wedge
Characterizes composite tuned reflections.
100
200
travel-time (ms)
0
travel-time (ms)
0
200
Processing can also artificially reduce frequency.
frequency
(Hz)
30
10
100
Gradational Wedge
travel-time (ms)
0
Response Attributes
• Characterize reflection zones contained within energy
envelope lobes.
• Include:
– response energy,
– response phase,
– response frequency,
– response length.
Response Attributes
Seismic
Trace
energy envelope trough positions
Reflection
Strength
Response
Attribute
One constant value per energy envelope.
Response Energy
Reflection Strength
Response Energy
• Maximum reflection strength within the envelope lobe.
Response Energy - Sensitivity
0
100
energy
2
0
100
0
0
100
100
0
travel-time (ms)
0
100
0
100
0
100
sensitive to:
• energy
Response Energy
Blocky Wedge
100
Exposes classic tuning behaviour.
Blocky/Gradational Wedge
200
Lateral variations indicate changes
in acoustic contrasts and bed thickness.
Gradational Wedge
200
0
100
Objectively
auto-picks and characterizes the zone-of-interest .
200
2
travel-time (ms)
100
0
travel-time (ms)
0
travel-time (ms)
0
energy
2
0.7
0
0
Response Phase
Instantaneous Phase
Reflection Strength
180
Response Phase
0
-180
• The value of the instantaneous phase at the point at
which the envelope is a maximum.
•A measure of the dominant phase of the waveform
contained within the energy envelope lobe.
Response Phase - Sensitivity
0
100
0
phase
(degrees)
180
100
0
0
100
100
0
travel-time (ms)
0
-180
100
0
100
0
100
sensitive to:
• phase
Response Phase
Blocky Wedge
100
Sharp lateral changes
can indicate detection-to-resolution transitions.
Blocky/Gradational Wedge
200
Lateral variations reveal changes in tuning.
100
200
travel-time (ms)
0
travel-time (ms)
0
200
Objectively
auto-picks and characterizes the zone-of-interest .
phase
(degrees)
180
0
-180
100
Gradational Wedge
travel-time (ms)
0
Response Frequency
Instantaneous Frequency
Reflection Strength
Response Frequency
• The value of the instantaneous phase at the point at
which the envelope is a maximum.
•A measure of the dominant frequency of the waveform
contained within the energy envelope lobe.
Response Frequency - Sensitivity
0
100
0
frequency
(Hz)
25
100
0
100
100
0
travel-time (ms)
0
10
100
0
100
0
100
sensitive to:
• bandwidth
Response Frequency
Blocky Wedge
100
200
Emphasizes tuning characteristics.
Blocky/Gradational Wedge
Characterizes composite tuned reflections.
100
200
travel-time (ms)
0
travel-time (ms)
0
200
Objectively
auto-picks and characterizes the zone-of-interest .
frequency
(Hz)
30
10
100
Gradational Wedge
travel-time (ms)
0
Response Attributes
• As a group, response energy, response phase, and
response frequency describe the complementary
dominant seismic characteristics within an energy
envelope.
– Response energy is sensitive to maximum energy;
– Response phase is sensitive to dominant phase; and
– Response frequency is sensitive to dominant
frequency.
Response Length
Reflection Strength
Response Length
• Half-length of the energy envelope lobe.
Response Length - Sensitivity
0
100
0
duration
(milliseconds)
51
100
0
100
100
0
travel-time (ms)
0
16
100
0
100
0
100
sensitive to:
• bandwidth
Response Length
Blocky Wedge
100
Exposes detection-to-resolution transitions.
Blocky/Gradational Wedge
200
0
200
100
Objectively
200
auto-picks and characterizes the zone-of-interest .
travel-time (ms)
0
travel-time (ms)
Gradational Wedge
duration
(milliseconds)
40
15
100
A measure of seismic waveform stability.
travel-time (ms)
0
Attribute Dependence
Attribute
Energy
real amplitude
quadrature amplitude
reflection strength
instantaneous phase
cosine of instantaneous phase
instantaneous frequency
response energy
response phase
response frequency
response length
Frequency
Phase
Summary
• Effective use of seismic attributes requires
understanding attribute sensitivity.
• Simple models allow geoscientists to examine and
understand attribute sensitivity.