Magneto-hydrodynamic Seismic Source Low-Frequency Generation
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Solution Overview
Problem
Conventional marine seismic sources, such as airguns and marine vibrators, are limited in generating low-frequency seismic energy, typically below 5 Hz, due to physical constraints and interference issues, which hinders the detection of gradual changes in subsea geological features and complicates Full Waveform Inversion processing.
Innovation Solution
A magneto-hydrodynamic seismic source is developed, comprising a casing with a fluid flow channel and superconducting electromagnets generating a uniform magnetic field, allowing for a continuously varying electric field to drive seawater flow and produce seismic signals with frequencies less than 5 Hz, overcoming the limitations of existing sources by controlling the Lorentz force and avoiding compressibility issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional airguns are used to generate seismic signals, then the source can be operated at intermittent time intervals to produce pressure waves, but the source cannot generate low frequency seismic energy below 5 Hz due to bubble oscillation frequency limitations
Solution Approach 1:
The patent replaces the mechanical bubble oscillation system with an electromagnetic actuation system. Instead of relying on air bubble oscillation to generate seismic signals, the invention uses an electromagnetic force generator that directly actuates a piston to displace water, thereby eliminating the frequency limitations imposed by bubble physics and enabling generation of low frequency signals below 5 Hz.
Solution Approach 2:
The patent changes the fundamental operating parameter from pressure-driven bubble oscillation to electromagnetic force-driven piston motion. This parameter change allows continuous control of the seismic signal frequency and amplitude, enabling generation of low frequency signals that were previously inaccessible to conventional airguns while maintaining the ability to operate at intermittent time intervals.
2Volume of moving object
If airguns are towed deeper below the water surface to generate larger bubbles, then the seismic signal volume increases, but the pressure on the air bubbles increases making it more difficult to generate low frequency signals
Solution Approach 1:
The patent eliminates the air bubble system entirely and replaces it with an electromagnetic actuation system. The electromagnetic force generator directly drives a piston that displaces water to generate seismic signals, removing the pressure-volume relationship that plagues conventional airguns and enabling low frequency generation regardless of operating depth.
Solution Approach 2:
The patent introduces an electromagnetic force generator as an intermediary between the power source and the water displacement mechanism. This intermediary converts electrical energy to mechanical force through electromagnetic interaction, providing direct control over piston motion and water displacement without being constrained by the pressure-volume relationship of compressed gas bubbles.
3Measurement precision
If marine vibrators are used to generate controlled waveforms, then the waveform can be precisely controlled, but the device cannot generate low frequency seismic energy below 10 Hz due to power requirements and fluid volume shifting difficulties
Solution Approach 1:
The patent replaces the hydraulic actuation system with an electromagnetic actuation system. Instead of using hydraulic pressure to move a piston, the invention uses electromagnetic force to directly actuate the piston, eliminating the fluid volume shifting limitations and reducing power requirements at low frequencies while maintaining precise waveform control.
Solution Approach 2:
The patent changes the actuation mechanism from hydraulic to electromagnetic, fundamentally altering how the piston is driven. This parameter change enables precise control of waveform generation at low frequencies by directly controlling electromagnetic force rather than relying on hydraulic fluid compressibility and volume changes, which become problematic at low frequencies.
4Adaptability or versatility
If impulsive seismic sources are used to generate broadband signals, then the source can produce pressure waves with variable frequency content, but the waveform cannot be precisely controlled and is either on or off
Solution Approach 1:
The patent introduces dynamic control capability to the seismic source through electromagnetic actuation. The electromagnetic force generator can be continuously adjusted in magnitude and frequency, allowing the piston motion and resulting seismic waveform to be precisely controlled in real-time. This dynamic control enables the source to generate variable frequency content while maintaining precise waveform control, overcoming the binary on/off limitation of impulsive sources.
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
The magneto-hydrodynamic seismic source enables the generation of broadband seismic signals, improving the characterization of subsea geological features and facilitating more accurate Full Waveform Inversion by providing low-frequency data, thus enhancing the resolution of geological models and reducing processing time and costs.
Implementation Method 1
A magneto-hydrodynamic seismic source is developed, comprising a casing with a fluid flow channel and superconducting electromagnets generating a uniform magnetic field, allowing for a continuously varying electric field to drive seawater flow and produce seismic signals
Data Source
AI summary
A magneto-hydrodynamic seismic source includes a casing having a central longitudinal axis; a fluid flow channel, and a plurality of electromagnets arranged along the channel for generating a uniform magnetic field at right angles to the central longitudinal axis of the channel, a first electrode positioned on a first side of the fluid flow channel, the first electrode being positioned opposite a second electrode that is positioned on a second opposing side of the fluid flow channel, and a controllable power source in electrical communication with the first electrode and the second electrode for generating a continuously varying electric field between the first electrode and second electrodes to generate a continuously varying inflow of seawater into the first end of the fluid flow channel with a corresponding continuously varying outflow of seawater in the form of a seismic signal being produced from the second end of the fluid flow channel.