Tilt Estimation in Multi-Sensor Streamers Using Hydrophone Coherence
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Solution Overview
Problem
Current methods for estimating tilt and pitch angles in multi-sensor streamers for marine seismic prospection require additional sensors or complex mechanical arrangements, which are costly, cumbersome, and difficult to calibrate accurately at sea.
Innovation Solution
A method that estimates tilt and pitch angles using low-frequency oscillations of the streamer, analyzing hydrophone and particle motion sensor data to compute tilt angles without a collocated tilt sensor, allowing for in-sea calibration and quality checking of angular offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a nearly collocated tilt sensor is used to measure tilt angle, then tilt measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses a tilt sensor at a different location (separated by distance L along the streamer) to measure tilt angle, creating a virtual copy of the particle motion sensor's orientation state. This allows tilt measurement without requiring a sensor to be physically collocated with the particle motion sensor, thereby reducing device complexity while maintaining measurement capability
Solution Approach 2:
The patent introduces an intermediary mathematical model that relates the tilt angle measured at one location to the particle motion sensor orientation at another location. This model accounts for the spatial separation and allows accurate tilt estimation without direct physical collocation, resolving the contradiction between measurement accuracy and device complexity
2Stability of the object's composition
If a gimbal mount with lubricant damping fluid is used to maintain sensor orientation, then sensor orientation stability is improved, but device complexity and space requirements increase
Solution Approach 1:
The patent replaces the mechanical gimbal mounting system with a mathematical/software-based solution. Instead of using physical gimbals with lubricant damping fluid to maintain sensor orientation, the invention uses coordinate transformations and tilt angle calculations to achieve the same orientation stability, thereby eliminating complex mechanical parts and reducing space requirements
Solution Approach 2:
The patent dynamically calculates the tilt angle based on real-time measurements from the tilted particle motion sensor and hydrophone, rather than relying on static mechanical constraints. This dynamic approach allows the system to adapt to changing conditions without requiring complex mechanical orientation maintenance systems
3Adaptability or versatility
If additional sensors are added to the streamer, then measurement capability is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent makes the existing tilted particle motion sensor and hydrophone perform multiple functions. The tilted particle motion sensor simultaneously measures both particle motion and provides tilt information through mathematical processing, while the hydrophone provides both pressure measurements and serves as a reference for tilt calculations. This multi-functionality eliminates the need for additional dedicated tilt sensors, reducing manufacturing cost and device complexity while maintaining enhanced measurement capability
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 accurate tilt and pitch angle estimation without additional sensors, reducing complexity and cost, and allowing for real-time calibration and quality assessment during marine operations.
Implementation Method 1
The particle motion sensor PMS is for example a 2-axis accelerometer that measures seismic signal
Implementation Method 2
The tilt angle β of the particle motion sensor PMS (also referred to as the angular position of the particle motion sensor) is formed by the Z sensing axis and the gravity vector (Z0=g)
Implementation Method 3
The streamers support pressure sensors such as hydrophones to detect seismic signals corresponding to pressure waves
Data Source
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AI summary
A method for estimating a tilt angle β(t) of at least one given particle motion sensor nearly collocated, in a multi-sensor streamer for seismic prospection, with a pressure sensor. The given particle motion sensor has two orthogonal sensing axes Y and Z in a plane orthogonal to a longitudinal axis of the streamer. The tilt angle is formed by the Z sensing axis and a reference vertical axis Z0. The method comprises, for the given particle motion sensor, a step of computing a first estimate β0 of the tilt angle, comprising: obtaining (41) first data measured by the pressure sensor nearly collocated with the given particle motion sensor; obtaining (42) second and third data measured by the given particle motion sensor along the sensing axes Y and Z respectively; for at least two values of a rotation angle θ, rotating (45) the second and third data by the rotation angle θ, to obtain rotated second and third data; and computing (46-410) a particular value θmax among the at least two values of the rotation angle, which maximizes, over at least one frequency, a coherence function between the first data and the rotated third data, or between the first data and velocity data resulting from an integration of the rotated third data, the particular value θmax being equal to said first estimate β0.