Seismic Reflection:Processing and Interpretation
Katie WooddellUW Madison
Objectives
• Develop a velocity model of the Santa Fe River Canyon to aid in structure interpretation
• Use predictive deconvolution to remove multiple reflections from the data
Processing StepsDefine
Geometry
Kill Bad Traces
CMP Gather
NMO Correction / Velocity Analysis
Predictive Deconvolution /Butterworth Filter
CMP Gather
NMO Correction / Velocity Analysis
Processing StepsDefine
Geometry
Kill Bad Traces
CMP Gather
NMO Correction / Velocity Analysis
Predictive Deconvolution /Butterworth Filter
CMP Gather
NMO Correction / Velocity Analysis
Defining Geometry
Processing StepsDefine
Geometry
Kill Bad Traces
CMP Gather
NMO Correction / Velocity Analysis
Predictive Deconvolution /Butterworth Filter
CMP Gather
NMO Correction / Velocity Analysis
Killing Traces
• Vibroseis signal had to be eliminated
• Channels showing large amounts of noise were deleted
Processing StepsDefine
Geometry
Kill Bad Traces
CMP Gather
NMO Correction / Velocity Analysis
Predictive Deconvolution /Butterworth Filter
CMP Gather
NMO Correction / Velocity Analysis
Predictive DeconvolutionWhat does it do?
Clears seismic data by predicting and eliminating multiple reflections
How does it work?
A filter is designed that recognizes and eliminates repetitions in the signal
Deconvolution Equation
Robertson 1998
To Conceptualize. . .
INPUT
* FILTER =OUTPUT
Deconvolution ResultsLocation 109
Tim
e (m
s)
DECONVOLVEDNO DECONVOLUTION
Location 109T
ime
(ms)
Processing StepsDefine
Geometry
Kill Bad Traces
CMP Gather
NMO Correction / Velocity Analysis
Predictive Deconvolution /Butterworth Filter
CMP Gather
NMO Correction / Velocity Analysis
Butterworth Filter
• Bandpass Filter
• Passes frequencies in the range of the vibroseis sweep (30-300 Hz)
• Effective in eliminating the noise amplified during predictive deconvolution
Butterworth Filtering
No Filter Butterworth Filter
Location 109
Tim
e (m
s)
Location 109
Tim
e (m
s)
Processing StepsDefine
Geometry
Kill Bad Traces
CMP Gather
NMO Correction / Velocity Analysis
Predictive Deconvolution /Butterworth Filter
CMP Gather
NMO Correction / Velocity Analysis
Processing StepsDefine
Geometry
Kill Bad Traces
CMP Gather
NMO Correction / Velocity Analysis
Predictive Deconvolution /Butterworth Filter
CMP Gather
NMO Correction / Velocity Analysis
NMO Correction
• NMO corrects for the delay in first arrival times
• NMO shifts the arrival times according to a specific stacking velocity
• This is an important step in the velocity analysis
Processing StepsDefine
Geometry
Kill Bad Traces
CMP Gather
NMO Correction / Velocity Analysis
Predictive Deconvolution /Butterworth Filter
CMP Gather
NMO Correction / Velocity Analysis
Velocity Analysis
• A Constant Velocity Analysis was conducted on both deconvolved and non-deconvolved data
• The following NMO stacking velocities were run for each situation:- 1000 m/s -1200 m/s
- 1400 m/s -1600 m/s
- 1800 m/s -2000 m/s
- 2200 m/s -2400 m/s
Conclusions
• Predictive deconvolution is an effective tool for eliminating multiples from seismic data
• A combination of the 2000 m/s and the 1600 m/s constant velocity models seems to produce a high resolution model
• This implies a higher average velocity medium on the east side of the fault, giving evidence that the normal La Bajada fault is being imaged
And a Special Thanks To. . .
The SAGE professors for their knowledge and patience
Team 5 for their hard work and some good times
Michelle Herrera, my Processing partnerLauren Larkin, who was more enthusiastic
about splicing together my seismic sections than I was