Phase-Shifted Seismic Sweeps for Noise Attenuation
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Solution Overview
Problem
Seismic surveys face challenges in effectively attenuating noise from seismic data, particularly due to energy from multiple seismic sources being filtered out during source separation, and residual shot noise that complicates the identification of subterranean geological formations and hydrocarbon deposits.
Innovation Solution
The method involves varying the phases of seismic source frequency sweeps in a predetermined sequence during towed seismic surveys, allowing for source separation and noise attenuation through frequency-wavenumber filtering, enabling the separation of energy from different sources and reducing residual shot noise without sacrificing spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple seismic sources are used simultaneously to improve survey efficiency, then productivity increases, but noise from multiple sources complicates data processing and reduces measurement precision
Solution Approach 1:
The patent segments the seismic survey into multiple channels, each assigned to a specific seismic source. By varying the phase of each source and assigning it to a specific channel, the system can separate and process signals from multiple sources independently, maintaining data quality while improving survey efficiency
Solution Approach 2:
The patent changes the phase parameter of each seismic source in a predetermined sequence. This phase variation creates distinct signal characteristics for each source, enabling separation and filtering of individual source signals from the combined data, thus resolving the contradiction between using multiple sources and maintaining measurement precision
2Object-affected harmful factors
If source separation filtering is applied to remove energy from multiple seismic sources, then noise attenuation improves, but spatial resolution is degraded
Solution Approach 1:
The patent applies phase shifts to seismic sources rather than traditional amplitude-based filtering. This parameter change allows separation of source signals in the phase domain, which preserves spatial information better than conventional filtering methods that operate in the amplitude domain
Solution Approach 2:
The patent replaces traditional mechanical filtering approaches with phase-based signal separation. By using phase variations and phase-correlated filtering, the system achieves noise attenuation while preserving the spatial characteristics of the seismic signals
3Measurement precision
If residual shot noise is reduced through conventional filtering, then signal quality improves, but the filtering process removes useful signal energy along with noise
Solution Approach 1:
The patent changes from amplitude-based filtering to phase-based filtering. By varying the phase of individual seismic sources and using phase-correlated filtering, the system can identify and remove residual shot noise while preserving the useful signal energy that maintains coherent phase relationships
Solution Approach 2:
The patent uses phase information as feedback to guide the filtering process. The phase variations introduced by the predetermined sequence provide a reference that enables selective attenuation of noise components while preserving signal components, reducing energy loss compared to conventional filtering
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 enhances the quality of seismic data by effectively separating source energy and reducing noise, improving the imaging of subterranean geological formations and facilitating the identification of hydrocarbon deposits with increased efficiency and accuracy.
Implementation Method 1
The sources generate seismic waves, which propagate into the geological formations creating pressure changes and vibrations along their way
Implementation Method 2
Some seismic sensors are sensitive to pressure changes (hydrophones), others to particle motion (e.g., geophones)
Implementation Method 3
Some seismic sensors are sensitive to pressure changes (hydrophones), others to particle motion (e.g., geophones)
Implementation Method 4
allowing for source separation and noise attenuation through frequency-wavenumber filtering
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A technique includes towing at least one seismic source in connection with a survey of a structure; and operating the seismic source(s) to fire shots, where each shot is associated with a frequency sweep. The technique includes varying phases of the frequency sweeps from shot to shot according to a predetermined phase sequence to allow noise in an energy sensed by seismic sensors to be attenuated.