Particle Motion Sensor for Marine Seismic Multiple Mitigation
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Solution Overview
Problem
Conventional marine seismic surveying techniques face challenges in mitigating the adverse effects of 'multiples' or ghost reflections, which interfere with data accuracy, either by positioning streamers accurately or through predictive processing, both of which are cumbersome and costly.
Innovation Solution
Incorporating particle motion sensors, such as accelerometers, along the seismic streamers that can sense the vector and polarization of wavefronts, allowing for the differentiation between initial reflections and multiples, thereby reducing interference without the need for continuous monitoring or complex predictive methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If streamers are positioned at a depth of 4-5 meters to mitigate ghost reflections, then multiples are reduced, but streamer positioning becomes difficult and control is lost due to large inertia and environmental conditions
Solution Approach 1:
The patent changes the measurement parameter from scalar magnitude to vector quantity (particle motion vector with direction and polarization). This allows differentiation between upgoing and downgoing waves based on vector direction, enabling multiple mitigation without requiring specific streamer positioning depths.
Solution Approach 2:
The patent replaces the mechanical positioning system (physical streamer depth control) with a sensor-based measurement system (particle motion sensors measuring vector quantities). This substitution eliminates the need for precise mechanical positioning while achieving multiple mitigation through vector analysis.
2Reliability
If predictive processing techniques are used to back out multiples during processing, then multiples are reduced, but processing time and costs increase due to complicated algorithms and assumptions
Solution Approach 1:
The patent performs the multiple mitigation action during data acquisition rather than during post-processing. By measuring particle motion vectors directly during the survey, the information needed to separate multiples is captured upfront, eliminating the need for time-consuming predictive processing algorithms later.
Solution Approach 2:
The particle motion sensors automatically capture both upgoing and downgoing wave information simultaneously during acquisition. The system self-contains all necessary information for multiple mitigation in the vector measurements, eliminating dependence on external predictive processing techniques.
3Device complexity
If conventional acoustic sensors are used that only measure wavefront magnitude, then data collection is simple, but multiples cannot be differentiated from reflections causing destructive interference
Solution Approach 1:
The patent adds a new dimension to the measurement by transitioning from scalar magnitude measurements to vector measurements (adding directional information). This dimensional enhancement allows the sensors to distinguish between upgoing reflections and downgoing multiples based on vector direction, improving data accuracy while maintaining sensor simplicity.
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 data accuracy by directly measuring wavefront direction, reducing the impact of multiples and streamer positioning complexities, leading to more reliable seismic data collection with reduced processing costs and increased operational efficiency.
Implementation Method 1
an accelerometer capable of sensing a particle motion vector from a change in position
Implementation Method 2
The sensor is designed to be buoyant or neutrally buoyant in water
Data Source
AI summary
A particle motion sensor, includes: a sensing element capable of sensing a particle motion vector from a change in position thereof, and a packing material in which the sensing element is positioned, wherein the particle motion sensor is symmetric about its longitudinal axis and has a center of gravity coincident with its volumetric center. An apparatus includes a streamer; a plurality of acoustic sensors distributed along the streamer; and a plurality of particle motion sensors distributed along the streamer, at least one particle motion sensor being symmetric about its longitudinal axis and having a center of gravity coincident with its volumetric center.