Magnetic Core Residual Magnetization for Transient EM Logging
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Solution Overview
Problem
Existing electromagnetic induction well logging technologies face challenges in generating a strong, rapidly reversible magnetic dipole moment to achieve deep and broad spatial range measurements, especially in the presence of conductive support or casing, which limits their ability to effectively investigate earth formations.
Innovation Solution
A transmitter antenna assembly with a magnetic core having residual magnetization is used, allowing for magnetization reversal and maintaining a constant magnetic dipole moment without power expenditure during steady-state phases, enabling efficient generation and rapid switching of a large magnetic dipole moment, and a method utilizing magnetization reversal in drill collars to facilitate deep-looking measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If high permeability magnetic material is used to increase magnetic dipole moment, then magnetic dipole moment is improved, but inductance increases and voltage becomes inappropriately high
Solution Approach 1:
The patent applies periodic action by using alternating current to periodically magnetize and demagnetize the magnetic core, creating transient electromagnetic signals. The current is switched between positive and negative pulses, causing the magnetic core to alternate its magnetization state, which generates the necessary electromagnetic induction in the formations while avoiding continuous high voltage requirements
Solution Approach 2:
The patent utilizes phase transitions in the magnetic core by exploiting hysteresis effects. The magnetic core transitions between magnetized and demagnetized states during each AC cycle, with the hysteresis loop enabling the core to retain some magnetization (residual magnetization) after current reversal, thereby maintaining magnetic dipole moment without continuous power input
2Force
If more turns in antenna coil are used to increase magnetic dipole moment, then magnetic dipole moment is improved, but inductance increases and dissipative power loss increases
Solution Approach 1:
The patent replaces the conventional approach of increasing magnetic dipole moment through more coil turns with a magnetic core-based system. The magnetic core provides the necessary magnetic path and enhances the dipole moment through its high permeability and hysteresis properties, eliminating the need for high-turn coils that would cause excessive inductance and resistive losses
Solution Approach 2:
The patent employs composite magnetic structures combining high permeability magnetic material with the antenna coil. This composite approach allows the magnetic core to concentrate magnetic flux and provide the necessary dipole moment while the coil provides only the necessary excitation current, significantly reducing overall power loss compared to air-core coils with many turns
3Ease of operation
If conductor parts are added to facilitate additional logging instrument, then ease of operation is improved, but signal generation and reception are affected
Solution Approach 1:
The patent introduces a non-conductive, non-magnetic intermediary material (such as plastic or ceramic) between the antenna coils and the drill collar or casing. This intermediary layer prevents direct electromagnetic coupling between the conductive drill collar/casing and the antenna, blocking the formation of eddy currents that would otherwise interfere with the electromagnetic signals while still allowing the drill collar to provide mechanical support
4Use of energy by moving object
If magnetization reversal is used to maintain constant magnetic dipole moment, then power consumption is reduced, but device complexity increases
Solution Approach 1:
The patent applies self-service by utilizing the inherent hysteresis properties of the magnetic core material to maintain magnetization without continuous external energy input. Once the magnetic core is magnetized by the AC current, its residual magnetization automatically maintains the magnetic dipole moment during the steady-state phase, with the core itself providing the necessary magnetic field without requiring continuous power consumption
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 significantly reduces power consumption and enables deeper penetration into earth formations, achieving highly effective electromagnetic induction transient measurements with reduced power loss and improved stability, even in the presence of conductive materials.
Implementation Method 1
the new vector of magnetic dipole of the antenna maintains constant (steady-state phase of the antenna dipole) due to substantial magnetic hysteresis and residual magnetization of magnetic material employed for the magnetic core
Implementation Method 2
An induction antenna, used for both transmitting and receiving signals in an induction well logging instrument can be thought of as a magnetic dipole
Implementation Method 3
Yet another effect of a high permeability magnetic material is to concentrate magnetic flux, thus substantially preventing exposing conductive parts of the antenna assembly to alternating magnetic field of the antenna coil, which would otherwise produce undesired eddy currents in the conductive parts
Data Source
AI summary
A transmitter antenna assembly for transient electromagnetic well logging instrument comprises an antenna coil coupled with a current source and a magnetic core having residual magnetization. Switching current in the antenna coil results in magnetization reversal in the magnetic core and change in magnetic dipole moment of the antenna. After the magnetization reversal is complete the current is removed and the new vector of magnetic dipole of the antenna maintains constant (steady-state phase of the antenna dipole) due to magnetic hysteresis of magnetic material employed for the magnetic core. No power expenditure during the steady-state phase of the magnetic dipole facilitates highly effective generation and fast switching of a large magnetic dipole. The magnetic core also serves as a shield between the antenna coil and any conductive part of the antenna assembly. Embodiments suitable for measurement-while-drilling or measurements through casing make use of residual magnetization of magnetic drill collar or magnetic casing respectively.