Marine Seismic Source Rotor Stator Modulation
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Solution Overview
Problem
Existing methods for marine seismic surveys are unable to generate useful seismic signals at frequencies below 6 Hz, which limits the accuracy of seismic data inversion for estimating acoustic impedance as a function of depth or travel time.
Innovation Solution
A marine seismic source that uses a reservoir and pressure vessel system to modulate water flow into the ocean, employing a rotor and stator with overlapping apertures to produce a modulated pressure signal, allowing for the generation of seismic signals across a range of frequencies including very low frequencies, and includes buffering mechanisms to minimize static pressure fluctuations and enhance monopole acoustic radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional marine seismic source methods are used, then the device complexity remains manageable, but the frequency range is limited to above 6 Hz
Solution Approach 1:
The seismic source is divided into separate functional modules: a pressure vessel containing water, a gas supply system with reservoir and pump, and a flow modulation system with rotor-stator assembly. Each module operates independently but contributes to the overall low-frequency signal generation capability, allowing complex functionality to be achieved through coordinated simple components
Solution Approach 2:
The system employs dynamic flow modulation by rotating the rotor with time-varying aperture area relative to the stator aperture. The rotation speed and aperture geometry are dynamically adjusted to control the instantaneous flow rate, enabling continuous variation of signal frequency and amplitude to achieve broadband low-frequency coverage
2Quantity of substance
If the aperture overlap area is increased to enhance flow, then the flow rate increases, but the frequency modulation capability is reduced
Solution Approach 1:
The rotor is designed with a specific aperture geometry and rotation speed profile that dynamically varies the overlap area with the stator aperture. At certain rotation positions, the apertures fully overlap to maximize flow rate; at other positions, they partially overlap or do not overlap to reduce flow. This continuous dynamic variation enables frequency modulation while maintaining high peak flow rates
Solution Approach 2:
The rotating rotor periodically varies the aperture overlap area with the stator, creating a periodic modulation of water flow rate. By controlling the rotation speed and aperture geometry, the period and amplitude of flow modulation can be adjusted to generate seismic signals at desired frequencies while maintaining sufficient flow magnitude for strong signal radiation
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 production of seismic signals down to frequencies as low as 0.5 Hz, improving the accuracy of seismic data inversion and allowing for more comprehensive seismic surveys by effectively radiating sound at frequencies previously inaccessible.
Implementation Method 1
means to modulate the area of the flow path so as to modulate the flow of water from the reservoir into the body of water to produce a modulated pressure signal in the body of water
Implementation Method 2
water is caused to flow from the reservoir into the body of water by means of pressurised gas
Implementation Method 3
the plenum being capable of holding a sufficient volume of gas at a pressure substantially equal to that of the water at the point at which the duct area is modulated so as to reduce the resonant frequency of the water in the duct
Implementation Method 4
the source includes means to cause the rate of rotation of the rotor to change... To enable the source to radiate signals throughout the band of the frequencies
Data Source
AI summary
A very low frequency marine seismic source has a reservoir of water (47) feeding water to an aperture communicating with the surrounding water (13). The rate of water flow through the aperture is controlled by a rotor disc (11) and stator disc (9) having holes which overlap to a greater or lesser extent as the rotor rotates. The modulation of the flow of water produces a modulated pressure signal which is radiated into the surrounding water. The device is intended to produce acoustic signals over a band extending down to 0.5 Hz or lower.