Non-Contact Magneto-Dynamic Sensor for Borehole Vibration Measurement
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Solution Overview
Problem
Existing downhole seismic measurement techniques face challenges in accurately capturing acoustic signals due to the need for mechanical coupling of sensors with the borehole formation, which limits frequency bandwidth and introduces noise, requiring complex tool architectures and anchoring processes.
Innovation Solution
A non-contact magneto-dynamic sensor system that uses a coil excited by an electric current to measure time-varying impedance, allowing derivation of vibration magnitude and frequency without physical contact, utilizing the Lorentz force principle to detect velocity vectors of the borehole wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensors are mechanically coupled to the formation, then measurement quality is improved, but device complexity and anchoring requirements increase
Solution Approach 1:
The patent replaces mechanical coupling sensors with a magneto-dynamic sensor that uses electromagnetic fields to detect formation vibrations non-contactly. The sensor employs a coil that generates a magnetic field, and vibrations induce voltage changes in the coil according to Faraday's law, eliminating the need for mechanical anchoring while maintaining measurement capability
Solution Approach 2:
The patent introduces a magnetic field as an intermediary between the sensor and the formation. The coil generates a magnetic field that penetrates the borehole wall, and vibrations of the formation modulate this field, allowing indirect measurement without physical contact. This intermediary enables signal transmission through the borehole wall without mechanical coupling
2Measurement precision
If sensors are mechanically coupled to the formation, then vibration detection is improved, but frequency bandwidth is limited
Solution Approach 1:
The patent replaces mechanical sensors with an electromagnetic-based magneto-dynamic sensor that has no moving parts or mechanical coupling elements. The coil responds to magnetic field changes induced by formation vibrations across a broad frequency range, eliminating the frequency limitations inherent in mechanical sensor systems
Solution Approach 2:
The patent changes the measurement parameter from mechanical displacement or acceleration to electrical voltage induced by magnetic field modulation. This parameter change allows the sensor to respond to a wider frequency range since electrical circuits have much higher frequency response capabilities compared to mechanical systems
3Measurement precision
If mechanical coupling is used, then signal acquisition is improved, but noise from tool-body propagation increases
Solution Approach 1:
The patent replaces mechanical signal transmission through the tool body with electromagnetic field-based measurement. The coil detects formation vibrations directly through the borehole wall without mechanical connection to the tool body, preventing noise propagation from tool movements or handling
Solution Approach 2:
The patent extracts the sensing function from the mechanical tool body structure. The magneto-dynamic sensor measures formation vibrations independently of the tool body, separating the measurement system from the mechanical support structure that would otherwise transmit noise
4Measurement precision
If anchoring is required for each depth, then measurement accuracy is improved, but productivity decreases
Solution Approach 1:
The patent replaces mechanical anchoring requirements with a non-contact electromagnetic measurement system. The magneto-dynamic sensor can accurately measure formation vibrations while moving through the borehole at constant speed, eliminating the stop-and-go measurement process required by anchored sensors
Solution Approach 2:
The patent transitions from a static measurement approach (anchoring at each depth) to a dynamic measurement approach where the sensor continuously measures vibrations while moving. The electromagnetic sensor maintains measurement accuracy during motion, enabling continuous logging without repeated anchoring and relocation operations
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 faster and more efficient seismic surveys with improved signal quality, eliminating the need for clamping devices and allowing for logging while moving, thus simplifying tool architecture and enhancing measurement accuracy.
Implementation Method 1
The magneto-dynamic sensor comprises a coil excited by an electric current and a circuitry for outputting a signal corresponding to a time-varying impedance of the coil
Implementation Method 2
utilizing the Lorentz force principle to detect velocity vectors of the borehole wall
Data Source
AI summary
Methods and systems of measuring acoustic signals via a borehole wall are disclosed. One or more non-contact magneto-dynamic sensors are configured or designed for deployment at at least one depth in a borehole. The magneto-dynamic sensor comprises a coil excited by an electric current and a circuitry for outputting a signal corresponding to a time-varying impedance of the coil. A processor is configured to perform signal processing for deriving at least one of a magnitude or a frequency of vibration of the borehole wall based on the output signal from the circuitry.