Marine Seismic Streamer Deghosting via Low Frequency Compensation
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Solution Overview
Problem
Marine seismic surveys face challenges in obtaining accurate high-resolution images of subterranean formations due to 'source ghosts' and 'receiver ghosts' that introduce spectral notches, amplifying or attenuating frequencies and complicating the interpretation of seismic signals.
Innovation Solution
Computational methods and systems for receiver deghosting marine seismic streamer data, which remove receiver ghost signals independently of free surface conditions or streamer shape, using low frequency compensation to recover vertical velocity wavefield information typically lost in low signal-to-noise ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional seismic survey methods are used to record pressure and particle motion signals, then broad bandwidth data can be obtained, but low frequency noise contaminates the particle motion signals reducing signal-to-noise ratio
Solution Approach 1:
The patent uses pressure sensor signals as an intermediary to recover low frequency vertical velocity wavefield information. By computing vertical velocity from pressure signals in the low frequency range where particle motion signals are noisy, the method transfers information from the clean pressure channel to reconstruct the lost velocity information, effectively using pressure signals as a mediator to bypass the noisy particle motion measurements at low frequencies
Solution Approach 2:
The patent transforms the particle motion signals from the time domain to the frequency domain using Fourier transforms, allowing selective processing of different frequency components. By identifying and separating the low frequency noisy components from the high frequency clean components, the method changes the parameter representation to enable targeted noise removal and information recovery across different frequency bands
2Measurement precision
If receiver ghost notches are present in seismic signals, then frequency amplification and attenuation occur making accurate imaging difficult, but removing ghosts requires knowledge of free surface conditions which may not be available
Solution Approach 1:
The patent extracts and removes the receiver ghost components from the seismic signals by decomposing the recorded wavefield into up-going and down-going wave components. By identifying the ghost-related down-going components and separating them from the primary up-going signals, the method removes the harmful ghost notches and their associated frequency amplification and attenuation effects, leaving only the clean primary seismic signals for accurate imaging
Solution Approach 2:
The patent converts the harmful receiver ghost reflections into useful information by using the relationship between pressure and vertical velocity wavefields. The ghost signals, while causing spectral notches, provide additional constraints that can be used to solve for the unknown free surface conditions and wavefield components, ultimately enabling deghosting without requiring prior knowledge of surface conditions
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
Enables the removal of receiver ghost signals from seismic data without assuming specific free surface conditions, improving the accuracy and resolution of seismic images by compensating for low frequency noise and recovering lost wavefield information.
Implementation Method 1
Each streamer includes a number of sensors that measure pressure and vertical velocity wavefields
Implementation Method 2
The streamers include receivers that measure pressure and particle motion wavefields
Implementation Method 3
computing a gradient of the pressure wavefield
Implementation Method 4
Fourier transforms are used to transform the vertical velocity wavefield from the time domain to the frequency domain
Implementation Method 5
the up-going and down-going vertical velocity wavefield components are separated
Data Source
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Figure 3A
AI summary
Computational methods and systems for deghosting marine seismic streamer data are described. In particular, an exploration-seismology vessel tows a number of streamers that form a data acquisition surface located beneath a free surface. The methods computationally deghost or substantially remove receiver ghost signals from seismic data recorded by steamer receivers. The deghosting methods include low frequency compensation to recover vertical velocity wavefield information that is typically lost due to a low signal-to-noise ratio over a low frequency range independent of the free surface conditions or the shape of the data acquisition surface.