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Seismic DSP Techniques Explained

This document discusses digital signal processing techniques for seismic waves. It begins with an overview of digital signal processing and its goals of measuring, filtering, and compressing analog signals. It then discusses seismic waves and the different types of seismic waves. The document outlines the basic scheme of seismic data processing, which includes loading data, demultiplexing, editing, filtering, deconvolution, velocity analysis, stacking, migration, and post-processing. It provides examples of editing/DMO correction, the effect of DMO on velocity spectra and gathers, predictive deconvolution, deconvolution equations, processing steps, results of deconvolution and filtering, and velocity analysis.

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Kapil Sharma
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555 views16 pages

Seismic DSP Techniques Explained

This document discusses digital signal processing techniques for seismic waves. It begins with an overview of digital signal processing and its goals of measuring, filtering, and compressing analog signals. It then discusses seismic waves and the different types of seismic waves. The document outlines the basic scheme of seismic data processing, which includes loading data, demultiplexing, editing, filtering, deconvolution, velocity analysis, stacking, migration, and post-processing. It provides examples of editing/DMO correction, the effect of DMO on velocity spectra and gathers, predictive deconvolution, deconvolution equations, processing steps, results of deconvolution and filtering, and velocity analysis.

Uploaded by

Kapil Sharma
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PPT, PDF, TXT or read online on Scribd
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DIGITAL SIGNAL PROCESSING OF SEISMIC WAVES

CONCEPTION AND REALISATION PRESENTED BY


pasha

WHAT IS DIGITAL SIGNAL PROCESSING


Representation of discrete time signals by a sequence of numbers 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)

1. 2. 3. 4.

DSP domains: basically it has 4 domains;


Time(t) domain(1-D signal) Frequency(f) domain Spatial domain(multi-D signal) Wavelet domain.

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.

Types of Seismic waves


1. BODY WAVES Primary waves(P-WAVES) Secondary waves(S-WAVES) 2. SURFACE WAVES Love waves Rayleigh waves

BASIC SCHEME OF SEISMIC DATA PROCESSING


Loading of the data/conversion Demultiplexing Geometry Editing Amplitude correction Frequency filter Deconvolution CMP-Sorting Velocity analysis NMO/DMO-Correction Stacking Migration Post-processing Measure

Pre-Processing

Prestack

Poststack

Printing/storage

Printing/storage

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 DMO CORRECTION WITH DMO CORRECTION

EFFECT OF DMO CORRECTION ON CMP GATHERING


WITHOUT DMO CORRECTION WITH DMO CORRECTION

Predictive Deconvolution
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

Deconvolution Equation

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To Conceptualize. . .
INPUT OUTPUT

FILTER

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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 Results
Location 109 Location 109

NO DECONVOLUTION

Time (ms)

DECONVOLVED 13

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
Location 109 Location 109

Time (ms)

No Filter

Time (ms) Butterworth Filter

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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 - 1400 m/s - 1800 m/s - 2200 m/s -1200 m/s -1600 m/s -2000 m/s -2400 m/s

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