Marine Vibrator Phase Control for Crosstalk Reduction
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Solution Overview
Problem
Conventional marine seismic surveys using impulsive sources face limitations in data acquisition rate due to delays between source activations, which restricts the speed and efficiency of seismic data collection, especially in towed marine surveys.
Innovation Solution
The method involves controlling the phase shifts of seismic signals from multiple marine vibrators during frequency sweeps, allowing for simultaneous source activation with reduced crosstalk through carefully selected phase shifts that can be random or specifically chosen to cancel out interference during multi-channel filtering, enabling efficient separation of seismic data from overlapping sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If delays are introduced between source activations in conventional marine seismic surveys, then the energy from one source decays to acceptable level before the next source is activated, but the data acquisition rate is restricted and survey speed is limited
Solution Approach 1:
The patent changes the temporal parameter by eliminating delays between source activations, allowing simultaneous or near-simultaneous firing of multiple sources. This parameter change enables higher data acquisition rates while the processing methods compensate for the loss of temporal separation.
Solution Approach 2:
The patent replaces the mechanical/temporal separation method (using time delays between source firings) with a signal processing-based separation method. Instead of physically separating the sources in time, the system uses computational methods to separate the overlapping signals after acquisition, thereby substituting a mechanical approach with an information-processing approach.
2Productivity
If simultaneous source activation is used to increase data acquisition speed, then productivity increases, but crosstalk between sources occurs and signal separation becomes difficult
Solution Approach 1:
The patent converts the harmful crosstalk between simultaneous sources into a beneficial signal structure. By using controlled phase shifts and known source signatures, the overlapping signals create a predictable interference pattern that can be mathematically separated and removed during processing, transforming the harmful effect into a manageable and even useful component for source separation.
Solution Approach 2:
The patent introduces phase shifts as an intermediary mechanism to differentiate between simultaneous sources. By applying distinct phase shift patterns to each source, the system creates unique signal signatures that act as intermediaries for identification and separation, allowing the processing system to distinguish between overlapping sources without requiring temporal separation.
3Productivity
If multiple marine vibrators are activated simultaneously with different phase shifts, then data acquisition efficiency improves, but complex signal processing is required to separate and localize crosstalk
Solution Approach 1:
The patent applies phase shifts to source signals before activation as a preliminary action. This pre-processing step embeds identification markers in the signals that simplify the subsequent separation process. By preparing the signals with known phase relationships before they are emitted, the system reduces the computational complexity of the later processing stages compared to separating completely unstructured overlapping signals.
Data Source
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AI summary
Methods and apparatuses for acquiring marine seismic data to generate images or determine properties of an interior section of the Earth using simultaneous marine vibrator sweeps and methods for processing the acquired seismic data. Phase of sweeps produced by the marine vibrator(s) are controlled to provide for removal of crosstalk. The phases between marine vibrator sweeps may be random or controlled to have a predetermined/desired phase difference. The predetermined phases may be determined to minimize the crosstalk between sweeps based on known seismic velocity of the survey area.