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