Symmetrical FIR Filter for Seismic DC Offset Removal
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Solution Overview
Problem
Seismic data acquisition systems face challenges in effectively removing direct current (DC) offsets from seismic sensors, which can degrade data quality and introduce phase distortion, especially when dealing with large-scale seismic surveys that require accurate signal processing and analysis.
Innovation Solution
The implementation of a symmetrical-in-time finite impulse response (FIR) filter that approximates a sinc-in-frequency filter, using multiple filter stages of varying lengths to minimize signal ripple and align nulls, thereby mitigating sensor offsets without introducing phase distortion, allowing for continuous data processing with zero phase shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional DC offset filtering methods are used, then DC offsets are removed from seismic data, but phase distortion is introduced and low-frequency signal integrity is compromised
Solution Approach 1:
The filtering process is divided into multiple sequential stages, each with specific characteristics. The first stage uses a rectangular filter to remove DC offsets, followed by a second stage with a different rectangular filter to correct artifacts. This segmentation allows each stage to be optimized for its specific function while maintaining overall signal integrity.
Solution Approach 2:
A multi-stage filtering approach acts as an intermediary between raw seismic data and final processed output. The intermediate processing stages gradually remove DC offsets and correct artifacts without introducing phase distortion, preserving the integrity of the seismic signal throughout the transformation process.
2Measurement precision
If aggressive filtering is applied to remove DC offsets, then offset removal effectiveness increases, but signal distortion and harmonics are introduced
Solution Approach 1:
The filtering operation is segmented into multiple stages with increasing aggressiveness. The first stage applies a milder rectangular filter that removes DC offsets without introducing significant distortion. Subsequent stages apply progressively stronger filtering to address artifacts, ensuring that harmful effects are minimized at each step rather than introduced all at once.
Solution Approach 2:
The filtering approach uses partial action by applying multiple stages of filtering rather than a single aggressive filter. Each stage removes a portion of the DC offset and associated artifacts, achieving complete offset removal through cumulative partial actions that prevent signal distortion and harmonic introduction.
3Productivity
If continuous data processing is implemented, then productivity increases, but offset removal challenges persist across continuous streams
Solution Approach 1:
The filtering system operates continuously on incoming seismic data streams without interruption or batch processing. The multi-stage rectangular filtering approach maintains consistent offset removal performance across continuous data flows, ensuring that productivity increases do not compromise the precision or consistency of DC offset removal.
Data Source
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AI summary
Methods, systems, and devices for conducting a seismic survey. The system includes at least one seismic sensor configured to supply a signal responsive to reflections of acoustic energy from an earth surface; and at least one processor configured to: mitigate sensor offset from a sequence of samples representative of the signal by filtering the sequence of samples using a symmetrical-in-time finite impulse response (FIR) filter. The FIR filter may approximate a sinc-in-frequency filter. The at least one processor may be configured to process the sequence of samples using a plurality of filter stages that are rectangular in time. The length of one filter stage of the plurality of filter stages may be different than the length of another filter stage of the plurality of filter stages.