Seismic New

8/2/2019 Seismic New

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DIGITAL SIGNAL PROCESSING OF

SEISMIC WAVES

CONCEPTION AND

REALISATION

PRESENTED BY

pasha

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WHAT IS DIGITAL SIGNAL PROCESSING

Representation of discrete time signals by asequence ofnumbers or symbols,

and the processing of these signals.

The goal of DSP is usually to measure, filter and/or compress

continuous real-world analog signals.(includes seismic signal) DSP domains:basically it has 4 domains;

1. Time(t) domain(1-D signal)

2. Frequency(f) domain

3. Spatial domain(multi-D signal)

4. Wavelet domain.

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WHAT ARE SEISMIC WAVES

Waves of energy that travel through the earth,

Result of an earthquake, explosion, or a volcano that imparts

low-frequency acoustic energy.

They often have very low strength.

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Types of

Seismic waves

1. BODY WAVES

Primary waves(P-WAVES)

Secondary waves(S-WAVES)

2. SURFACE WAVES

Love waves

Rayleigh waves

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Loading of the data/conversion

Demultiplexing

Editing

Geometry

Amplitude correction

Frequency filter

Deconvolution

Velocity analysis

NMO/DMO-Correction

Stacking

Migration

Measure

Printing/storage Printing/storage

CMP-Sorting Prestack

PoststackPost-processing

Pre-Processing

BASIC SCHEME OF SEISMIC DATA PROCESSING

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EDITING OR

DMO

CORRECTION

A seismic processing operation

to correct for the fact

that, for dipping reflections,

the traces of a CMP

gather do not involve a

common reflection point.

DMO effectively corrects for

the reflection-point smear.

(a) Horizontal Reflector

CMP=CDP

(b)Dipping Reflector

CMPCDP

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EFEECT OF DMO CORRECTION ON

VELOCITY SPECTRUM

WITHOUT DMOCORRECTION

WITH DMOCORRECTION

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EFFECT OF DMO CORRECTION ON

CMP GATHERING

WITHOUT DMOCORRECTION WITH DMO CORRECTION

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PredictiveDeconvolution

What 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

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Deconvolution Equation

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ToConceptualize. . .

INPUT

* FILTER =

OUTPUT

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Processing Steps

Define

Geometry

Kill Bad Traces

CMP Gather

NMO Correction /

Velocity Analysis

Predictive Deconvolution /

Butterworth Filter

CMP Gather

NMO Correction /

Velocity Analysis

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Deconvolution ResultsLocation 109

Time(ms)

DECONVOLVEDNO DECONVOLUTION

Location 109

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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

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Butterworth Filtering

No Filter Butterworth Filter

Location 109

Time(ms)

Location 109

Time(ms)

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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

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Seismic New