Vertical Seismic Profile Shear-Wave Noise Attenuation
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Solution Overview
Problem
In the oil and gas industry, vertical seismic profiles (VSPs) often face challenges in separating and processing shear-wave vibrations from compressional waves, with shear waves acting as unwanted noise, which complicates imaging and converting surface seismic data to depth.
Innovation Solution
A method involving the transformation of multi-component VSP datasets into vertical and horizontal spectra, designing a band-pass filter based on the horizontal spectrum's energetic signal, and adaptively subtracting an estimated noise model from the vertical component to isolate and remove shear-wave contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If shear waves are recorded along with compressional waves in VSP data, then more complete seismic information is obtained, but shear waves act as unwanted noise that complicates imaging and data conversion
Solution Approach 1:
The patent segments the multi-component VSP data into vertical and horizontal spectral components, then applies selective filtering to the vertical component based on the horizontal spectrum's energetic signal characteristics. This segmentation allows the useful compressional wave information to be separated from the harmful shear wave noise in the frequency domain.
Solution Approach 2:
The patent extracts the shear wave noise component from the vertical VSP data by designing a band-pass filter based on the horizontal spectrum's energetic signal. The filter selectively removes the shear wave frequency components while preserving the compressional wave information, effectively taking out the harmful element from the data.
2Reliability
If a band-pass filter is designed based on the horizontal spectrum's energetic signal, then shear-wave noise is effectively attenuated, but the processing complexity increases
Solution Approach 1:
The patent uses the horizontal spectrum's energetic signal as an intermediary to guide the filter design for processing the vertical component. Instead of directly analyzing the vertical component for noise removal, the horizontal spectrum serves as a mediator that provides the filter parameters, simplifying the overall processing approach while maintaining effectiveness.
Solution Approach 2:
The patent performs preliminary transformation of both vertical and horizontal components into their spectral representations before filter design. This preliminary action in the frequency domain makes it easier to identify and attenuate shear wave noise, as the filtering operation can be performed more efficiently before returning to the time domain for final processing.
Data Source
AI summary
A method of determining a shear-wave attenuated vertical component vertical seismic profile (VSP) dataset is disclosed. The method includes, obtaining a multi-component VSP dataset, including a vertical and a horizontal component, transforming the vertical component into a vertical spectrum and the horizontal component into a horizontal spectrum, and designing a band-pass filter based, at least in part, on an energetic signal of the horizontal spectrum. The method further includes determining a muted vertical amplitude spectrum by applying the pass-band filter to an amplitude spectrum of the vertical spectrum, determining an estimated noise model based on the muted vertical amplitude spectrum and the vertical spectrum; and determining the shear-wave attenuated vertical component VSP dataset by adaptively subtracting the estimated noise model from the vertical component of the multi-component VSP dataset. A system including a seismic source, a plurality of seismic receivers, and a seismic processor for executing the method is disclosed.