Variable Mass Load Marine Vibrator for Depth-Dependent Resonance
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Solution Overview
Problem
Marine vibrators used in seismic surveys face challenges with air-spring effects that cause resonance frequency increases at depth, leading to inefficient energy transmission and limited operational range.
Innovation Solution
A variable mass load is added to the piston plate of marine vibrators to compensate for air-spring effects, shifting the resonance frequency lower and maintaining it within the desired seismic frequency range, independent of water depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If the marine vibrator is pressure balanced with external hydrostatic pressure at depth, then structural weight is minimized, but the air-spring effect increases causing resonance frequency to increase
Solution Approach 1:
A variable mass load is added to the piston assembly to counterbalance the increasing air-spring effect at depth. The mass load increases with depth to compensate for the stiffening air spring, thereby maintaining stable resonance frequency while the pressure-balanced structure minimizes structural weight.
Solution Approach 2:
The mass load is made variable rather than fixed, allowing it to change with operating depth. This dynamic adjustment compensates for the depth-dependent air-spring effect, enabling the system to maintain stable resonance frequency across different operating conditions while keeping the pressure-balanced lightweight structure.
2Weight of stationary object
If the bulk modulus of internal gas is increased to improve pressure balance, then structural weight is reduced, but energy transmission efficiency decreases due to increased air-spring effect
Solution Approach 1:
The variable mass load acts as a counterweight to the increased air-spring stiffness resulting from higher bulk modulus. By adding this mass, the system compensates for the energy loss caused by the stiff air spring, maintaining efficient energy transmission to the water while preserving the lightweight pressure-balanced structure.
Solution Approach 2:
The system changes the mass parameter dynamically with depth to compensate for changes in the air-spring parameter (bulk modulus). This parameter adjustment maintains optimal energy transmission efficiency despite the increased stiffness of the internal gas at greater depths.
3Adaptability or versatility
If pressure balance is maintained at greater depths, then operational depth capability is extended, but resonance frequency shifts out of the desired seismic frequency range
Solution Approach 1:
The variable mass load enables the system to adapt dynamically to different operating depths. As depth increases and pressure balance is maintained, the mass load increases to compensate for the air-spring effect, keeping the resonance frequency within the desired 1-100 Hz seismic range and extending operational depth capability.
Solution Approach 2:
The mass parameter is changed with depth to compensate for pressure-induced frequency shifts. This parameter adjustment allows the marine vibrator to operate reliably across a wide depth range while maintaining resonance frequency within the required seismic frequency band.
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 solution effectively maintains resonance frequency within the seismic frequency range of 1 Hz to 10 Hz, enhancing energy transmission efficiency and operational depth capability.
Implementation Method 1
the air-spring effect within the marine vibrator. As used herein, the term 'air spring' is defined as an enclosed volume of air that may absorb shock or fluctuations of load due to the ability of the enclosed volume of air to resist compression and decompression
Implementation Method 2
the stiffness of the acoustic components of the marine vibrator and the internal gas are the primary determining factors in the marine vibrator's resonance frequency
Data Source
AI summary
Embodiments relate to relate to marine vibrators that incorporate one or more piston plates that act on the surrounding water to produce acoustic energy. An example marine vibrator may comprise: a containment housing; a piston plate; a fixture coupled to the containment housing; a mechanical spring element coupled to the piston plate and the fixture; a driver disposed in the marine vibrator, wherein the driver is coupled to the piston plate and the fixture; and a container coupled to the piston plate, wherein the container is configured to hold a variable mass load; wherein the marine vibrator has a resonance frequency selectable based at least in part on the variable mass load.