Ultra-slim NMR Logging Tool with Expandable Antenna
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Solution Overview
Problem
Current NMR well logging tools face challenges in achieving a high signal-to-noise ratio (SNR) due to their large diameter, making them unsuitable for pipe assisted wireline applications, particularly in small diameter logging tools, which are necessary for high angle or horizontal wells.
Innovation Solution
An ultra-slim NMR well logging tool with a magnet and antenna designed to change configurations for passage through a drill string and measurement, featuring a retractable bow spring centralizer and axially symmetrical design with adjustable static and radio-frequency magnetic fields, enhancing the magnetic dipole moment and reducing magneto-acoustic ringing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the NMR tool diameter is reduced to enable pipe assisted wireline application, then the tool can be lowered through drill string, but the signal-to-noise ratio becomes unacceptably small
Solution Approach 1:
The magnet assembly is designed to change its magnetic moment dynamically between two states: a first state with reduced magnetic moment for passing through the drill string, and a second state with maximum magnetic moment for performing NMR measurements. This dynamic transformation allows the tool to overcome the contradiction by adapting its properties to different operational phases.
Solution Approach 2:
The invention changes the magnetic moment parameter of the magnet assembly between operational phases. By transforming the magnet assembly from a first configuration with reduced magnetic moment to a second configuration with maximum magnetic moment, the system optimizes both the ability to pass through the drill string and the signal-to-noise ratio during measurements.
2Power
If the magnet has maximum dipole moment during passage through drill string, then maximum magnetic field is generated, but the magnet gets stuck due to magnetic attraction force
Solution Approach 1:
The magnet assembly dynamically transforms between a first state with reduced magnetic moment for easy movement through the drill string and a second state with maximum magnetic moment for generating sufficient magnetic field during measurements. This dynamic adaptation resolves the contradiction between magnetic field strength and ease of movement.
Solution Approach 2:
The magnet assembly is preliminarily configured in a first state with reduced magnetic moment before entering the drill string to prevent magnetic attraction and facilitate smooth passage. After successfully passing through, the magnet transforms to the second state with maximum magnetic moment for measurement operations.
3Measurement precision
If the antenna is in open position configuration, then the magnetic dipole moment is greater enhancing NMR signal, but the antenna cannot be lowered through drill string
Solution Approach 1:
The antenna assembly dynamically transforms between a closed position configuration for passing through the drill string and an open position configuration for performing measurements with enhanced magnetic dipole moment and NMR signal strength.
Solution Approach 2:
The antenna assembly is nested in a closed position configuration within the tool body to enable passage through the drill string. Once in position, the antenna expands to an open position configuration, resembling a nested doll that transforms from a compact to an expanded state for measurement 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
The tool achieves a higher signal-to-noise ratio and prevents magnetic attraction issues, enabling effective NMR measurements in tight spaces with improved SNR, suitable for pipe assisted wireline applications.
Implementation Method 1
a magnet to generate static magnetic field
Implementation Method 2
measuring nuclear magnetic resonance properties of an earth formation
Implementation Method 3
an antenna to generate radio-frequency magnetic field
Implementation Method 4
RF voltages are induced in the receive antenna as a result of precessional rotation of nuclear spin axes
Data Source
AI summary
NMR properties of earth formations are determined using a logging device movable in a borehole. The logging device includes a magnet assembly to generate a static magnetic field and an antenna expandable from the surface of the magnet assembly into the borehole toward the borehole wall to increase the magnetic dipole moment of the antenna. The logging device can be lowered or raised through a drill pipe with the magnet assembly being configured to generate no magnetic field while the device is conveyed within the drill pipe. The logging device may also include a side-looking sensor to acquire fast relaxation component of the NMR signals.