Magnetic Sensor Conductivity Imaging Borehole
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Solution Overview
Problem
Existing well logging tools face challenges in accurately measuring conductivity in boreholes, particularly in thinly laminated sand-shale sequences and shaly-sand formations due to electrical anisotropy and issues with galvanic techniques in highly conductive formations and low conductive bore mud, leading to measurement errors and poor sensitivity.
Innovation Solution
A magnetic sensor with a C-shaped magnetic core and conductive inserts is used to generate a focused magnetic field for improved micro-conductivity measurements, featuring windings around the core and a conductive case to enhance sensitivity and reduce background noise, allowing for precise conductivity evaluation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If galvanic techniques are used for conductivity measurement, then the measurement method is simple, but measurement accuracy deteriorates in highly conductive formations and low conductive bore mud due to voltage drop and stray electric field
Solution Approach 1:
The patent replaces galvanic (electrical contact-based) measurement techniques with electromagnetic induction techniques. Instead of using direct electrical contact through electrodes, the invention uses induction sensors that generate AC magnetic fields to induce eddy currents in the formation, eliminating the problems of voltage drop and stray electric fields associated with galvanic methods.
Solution Approach 2:
The patent changes the measurement parameters from direct voltage measurement (galvanic) to electromagnetic field measurement (induction). By using AC magnetic fields at specific frequencies and measuring the induced eddy currents, the system achieves accurate conductivity measurements in conditions where galvanic methods fail.
2Area of stationary object
If induction sensors are used for conductivity measurement, then measurement coverage is improved, but sensitivity to wall conductivity variations deteriorates due to poor energy focusing
Solution Approach 1:
The patent applies local quality by designing the induction sensor with specific geometric characteristics that concentrate the AC magnetic field energy into a focused region near the borehole wall. The sensor geometry is optimized to create a localized measurement zone, improving sensitivity to wall conductivity variations while maintaining adequate measurement coverage.
Solution Approach 2:
The patent utilizes the spatial dimension by optimizing the sensor geometry and magnetic field distribution in three-dimensional space. By carefully designing the sensor structure, the magnetic field energy is distributed and focused in specific spatial regions, achieving both coverage and sensitivity through dimensional optimization.
3Measurement precision
If micro-conductivity imaging is performed to investigate small indications, then reservoir evaluation accuracy is improved, but measurement complexity and computational requirements increase
Solution Approach 1:
The patent performs preliminary action by collecting high-quality, high-resolution conductivity measurement data using the optimized induction sensor before interpretation. The sensor design and measurement methodology are optimized in advance to provide clean, reliable data that reduces the complexity of subsequent computational interpretation and modeling.
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 provides improved sensitivity and accuracy in micro-conductivity measurements by focusing the magnetic field and reducing measurement errors, achieving better vertical resolution and sensor quality factor compared to prior art, enabling more reliable data collection in borehole environments.
Implementation Method 1
probing with an induction-sensing coil that generates an AC magnetic field and corresponding eddy currents in the wall of the borehole
Implementation Method 2
generates an AC magnetic field and corresponding eddy currents in the wall of the borehole
Data Source
AI summary
A sensor for performing micro-conductivity measurements during well logging measurements in a borehole includes a magnetic core having a conductive insert wherein windings are driven with alternating current. Some embodiments include a sensor further having a conductive case. Various aspects of the sensor, such as dimensions and conductive properties of fabrication materials are selected to maximize performance of the sensor. Methods for using the sensor call for, among other things, placing the sensor in a well logging tool, and placing the tool in a well bore. A substantial focusing of the magnetic field on the wall of the borehole is achieved and provides for high quality data.