Seismic Source Separation Using Impulsive and Non-Impulsive Sources
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Solution Overview
Problem
Current marine survey technologies using air gun arrays are limited in generating acoustic energy at frequencies below 8 Hz, as increasing chamber volumes or pressures leads to impractical equipment sizes and reliability issues, hindering the expansion of the low-frequency range for illuminating subterranean formations.
Innovation Solution
The use of a combination of impulsive and non-impulsive sources, where the non-impulsive source generates acoustic energy over a broader frequency range, including frequencies below 8 Hz, by activating the impulsive source with time delays and the non-impulsive source continuously, allowing for separation of seismic data into distinct frequency bands using advanced signal processing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If air gun chamber volume is increased to generate lower frequency acoustic energy, then the low-frequency range is expanded, but the equipment size becomes impractical
Solution Approach 1:
The patent combines impulsive sources (air guns) with non-impulsive sources (marin e vibrators) to achieve low-frequency acoustic energy generation. The marine vibrators produce continuous low-frequency signals (including below 8 Hz) without requiring large chamber volumes, while air guns provide broadband high-frequency content. This merging allows the system to achieve low-frequency illumination through the vibrator rather than scaling up air gun sizes.
2Quantity of substance
If air gun charge pressure is increased to generate lower frequency acoustic energy, then the low-frequency range is expanded, but the reliability decreases
Solution Approach 1:
The patent introduces marine vibrators as an intermediary device to generate low-frequency acoustic energy. Instead of pushing air guns to extreme charge pressures that compromise reliability, the vibrator serves as a dedicated low-frequency source that operates reliably at continuous low frequencies, while air guns maintain their reliable impulsive operation at higher frequencies.
3Quantity of substance
If air gun chamber volume is increased to expand low-frequency range, then frequencies below 8 Hz can be generated, but the compressor capacity requirement increases substantially
Solution Approach 1:
The patent replaces the mechanical approach of using large-capacity compressors to fill large air gun chambers with an alternative mechanical system - marine vibrators that directly generate low-frequency acoustic energy through controlled mechanical oscillation of a water-gun interface. This substitution eliminates the need for substantial compressor capacity increases while achieving the same low-frequency generation goal.
4Adaptability or versatility
If multiple source types are used to expand frequency range, then the frequency spectrum coverage is improved, but the data separation complexity increases
Solution Approach 1:
The patent employs dynamic activation patterns where the impulsive source is activated with time delays and the non-impulsive source is activated continuously. This dynamic operation creates distinct temporal signatures for each source type in the recorded data, enabling separation through time-domain analysis and correlation techniques. The different activation patterns provide a dynamic basis for distinguishing and separating the source contributions despite the combined frequency spectrum.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively expands the low-frequency range of acoustic signals, enhancing the ability to illuminate subterranean formations with a broader frequency spectrum, improving the accuracy and reliability of marine surveys.
Implementation Method 1
When an air gun is triggered, air or gas is forced through vents into the water, creating a high-pressure, oscillating primary bubble followed by a foam of smaller oscillating secondary bubbles. The bubble oscillation period of a primary bubble produced by a single air gun may be related to the volume of the air gun chamber and charge pressure
Implementation Method 2
a non-impulsive source is simultaneously activated to generate a non-impulsive source wavefield
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
Methods and systems to separate seismic data associated with impulsive and non-impulsive sources are described. The impulsive and non-impulsive sources may be towed through a body of water by separate survey vessels. Receivers of one or more streamers towed through the body of water above a subterranean formation generate seismic data that represents a reflected wavefield produced by the subterranean formation in response to separate source wavefields generated by simultaneous activation of the impulsive source and the non-impulsive source. Methods and systems include separating the seismic data into impulsive source seismic data associated with the impulsive source and non-impulsive source seismic data associated with the non-impulsive.