Seismic Source Separation Using Modified Pseudorandom Sweeps

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Solution Overview

Problem

Conventional seismic exploration methods face issues such as poor source control, harmonic distortion, spatial resolution limitations, and increased acquisition time due to the use of multiple vibrators, which affect data quality and efficiency.

Innovation Solution

The method employs modified pseudorandom sequences for seismic acquisition, incorporating spectral reshaping, cross-correlation suppression, and level compression to minimize crosstalk and enhance source separation, using a pseudorandom number generator to generate weakly correlated sequences that are then modified and used to separate seismic data from multiple vibrators.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple vibrators are used simultaneously for seismic acquisition, then productivity increases, but source separation becomes difficult due to crosstalk

Engineering Contradiction:

Improvedata acquisition efficiencyVSAvoidsource separation accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent segments the seismic acquisition process by assigning unique pseudorandom sequences to each vibrator source. This allows simultaneous operation of multiple vibrators while maintaining the ability to separate their individual contributions through correlation processing, resolving the contradiction between productivity improvement and source separation accuracy

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the temporal and spectral parameters of the vibrator signals by using modified pseudorandom sequences with specific autocorrelation properties. This parameter modification enables clear separation of multiple sources even when they operate simultaneously, maintaining measurement precision while improving productivity

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If conventional swept sine wave signals are used, then data acquisition is simpler, but crosstalk between multiple sources increases

Engineering Contradiction:

Improveacquisition simplicityVSAvoidcrosstalk between sources

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The patent modifies the signal parameters by replacing conventional swept sine waves with pseudorandom sequences that have optimized autocorrelation properties. This change reduces crosstalk between multiple sources while maintaining ease of operation through systematic signal generation and processing methods

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes the conventional swept sine wave mechanical signaling approach with a pseudorandom sequence-based system. This substitution reduces harmful crosstalk effects while maintaining operational simplicity through digital signal generation and correlation-based separation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If multiple records are collected for source separation, then source separation accuracy improves, but acquisition time increases

Engineering Contradiction:

Improvesource separation accuracyVSAvoidacquisition time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent enables continuous useful action by allowing multiple vibrators to operate simultaneously without requiring sequential recording. The pseudorandom sequence correlation method extracts individual source contributions from the composite signal, achieving accurate source separation in a single continuous recording and eliminating time loss

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent applies preliminary action by designing pseudorandom sequences with specific autocorrelation properties before acquisition. This pre-planned signal structure enables efficient separation of multiple sources during processing, reducing the need for multiple records and minimizing acquisition time

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS7859945B2Efficient seismic data acquisition with source separation

Publication Date: 2010.12.28 SERCEL INC

AI summary

A method for the simultaneous operation of multiple seismic vibrators using unique modified pseudorandom sweeps and recovery of the transmission path response from each vibrator is disclosed. The vibrator sweeps are derived from pseudorandom binary sequences modified to be weakly correlated over a time window of interest, spectrally shaped and amplitude level compressed. Cross-correlation with each pilot signal is used to perform an initial separation of the composite received signal data set. Recordings of the motion of each vibrator are also cross-correlated with each pilot, windowed, and transformed to form a source cross-spectral density matrix in the frequency domain useful for source signature removal and for additional crosstalk-suppression between the separated records. After source signature removal in the frequency domain an inverse transform is applied to produce an estimate of each source-to-receiver earth response in the time domain. The method has application to both land and marine geophysical exploration.