Marine Seismic Source Rotary Valve Attenuates Out-of-Band Noise
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Solution Overview
Problem
Conventional marine seismic sources, such as airguns, emit significant high-frequency acoustic energy that is outside the frequency range of interest for seismic exploration, causing noise and potentially harming marine life, due to the rapid displacement of water volume by released compressed gas.
Innovation Solution
The implementation of seismic sources with specific designs, including an outer and inner cylinder configuration, a rotating axis bar, and controlled gas release mechanisms, to limit the rate of water displacement to less than 2.9 x 10^6 cubic-meters per second, thereby attenuating out-of-band frequencies. This is achieved through various configurations like rotary valve, gas piston, controlled combustion, and radial pipe seismic sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If compressed gas is released rapidly to generate acoustic pulses for seismic exploration, then the amplitude and energy of the seismic signal is improved, but out of band high frequency noise is generated and marine life is adversely affected
Solution Approach 1:
The airgun chamber is divided into multiple ports (e.g., first port and second port) that release compressed gas at different times. The first port releases gas to generate an initial acoustic pulse, while the second port releases gas after a time delay to generate a subsequent pulse. This segmentation of the gas release process allows control over the frequency content, reducing out of band high frequency energy while maintaining useful seismic signal energy.
Solution Approach 2:
The seismic source employs periodic gas release through multiple ports with controlled timing. The first port operates at a initial time to generate a primary acoustic pulse, and the second port operates after a predetermined time delay to generate a secondary pulse. This periodic action with controlled intervals shapes the frequency spectrum to attenuate high frequency noise while preserving useful mid-frequency seismic energy for exploration.
2Power
If the rate of water displacement is increased to enhance seismic signal strength, then the acoustic energy is improved, but out of band frequencies are emitted
Solution Approach 1:
The water displacement process is segmented into multiple phases corresponding to gas release from different ports. The first port displaces water at an initial rate to generate useful acoustic energy, while the second port displaces water after a time delay at a controlled rate. This segmentation allows the overall water displacement to generate strong acoustic signals while controlling the rate at any instant to avoid generating out of band high frequency noise.
Solution Approach 2:
The water displacement occurs in periodic bursts through controlled gas release from multiple ports. The first port creates a initial water displacement event, followed by a second port creating a subsequent displacement event after a predetermined interval. This periodic water displacement pattern generates strong acoustic energy while the controlled timing and rates prevent excessive high frequency content.
Data Source
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AI summary
A seismic source for marine seismic acquisition is described, comprising an outer cylinder having one or more apertures, an inner cylinder having one or more apertures configured to align with the apertures of the outer cylinder at one or more predetermined rotational positions of the inner cylinder, wherein an outer wall of the inner cylinder is flush with an inner wall of the outer cylinder, an axis bar coupled to the inner cylinder, wherein the axis bar rotates the inner cylinder, an actuator coupled to the axis bar, wherein the actuator controls a rate of rotation of the inner cylinder, and a gas supply coupled to the inner cylinder, wherein the gas supply provides a compressed gas inside the inner cylinder, wherein the compressed gas is released out of the seismic source such that a volume of water surrounding the seismic source is displaced at less than a predetermined rate, thereby attenuating an out of band frequency emitted by the seismic source.