Nuclear Magnetic Resonance Logging Probe Antenna Arrays
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Solution Overview
Problem
Nuclear magnetic resonance logging tools are limited to detecting signals only in radial and axial depth dimensions, lacking the capability to detect signals in the circumferential multi-azimuth sensitive area.
Innovation Solution
A nuclear magnetic resonance logging tool probe with a cylindrical magnet and an antenna array apparatus featuring multiple groups of antenna arrays distributed along the magnet's circumference, allowing for independent feeding and excitation of antennas to achieve mono-azimuth and multi-azimuth angle detection, and detection at different radial depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single antenna surrounds the magnet to excite polarized stratum regions all around (360 degrees) the borehole, then there is no detecting blind zone around the borehole and multi-frequency multi-slice measurement can be performed, but the measuring signal is only an average signal of signals in the 360-degree stratum and the tool cannot detect signals in the circumferential multi-azimuth sensitive area
Solution Approach 1:
The single antenna is segmented into multiple antenna arrays distributed along the circumference of the magnet. Each antenna array can be independently excited to detect signals from specific azimuth directions, transforming the averaged signal into separable directional signals while maintaining complete circumferential coverage.
Solution Approach 2:
The detection capability is extended from two dimensions (radial and axial) to three dimensions by adding circumferential azimuth detection. Multiple antenna arrays arranged circumferentially enable the tool to distinguish signals from different azimuth directions, adding the azimuth dimension to the detection space.
2Measurement precision
If multiple antenna arrays are distributed along the circumference of the magnet with independent feeding, then circumferential multi-azimuth detection capability is achieved, but the device complexity increases
Solution Approach 1:
The antenna system is divided into multiple independent antenna arrays positioned at different circumferential locations. Each antenna array is independently fed and can be excited separately, enabling directional signal detection from different azimuths while maintaining modular structure that manages complexity.
Solution Approach 2:
Each antenna array serves multiple functions: it can be independently excited for azimuth-specific detection, combined with other arrays for omnidirectional detection, and used for different radial depth detections through varying excitation patterns. This multi-functionality justifies the increased structural complexity.
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 improved circumferential recognition and three-dimensional stratum detection (radial, axial, and circumferential) by exciting different antenna arrays, enhancing the tool's detection capabilities.
Implementation Method 1
the magnet can form a static magnetic field for polarizing spinning hydrogen protons
Implementation Method 2
the antenna can emit a radio frequency field for turning the spinning hydrogen protons, after the radio frequency field is removed, the spinning hydrogen protons start to precess along the static magnetic field, thus generate nuclear magnetic resonance inductive signals
Data Source
AI summary
The present invention provides a multi-detecting depth nuclear magnetic resonance logging tool and probe, and an antenna excitation method, the probe of nuclear magnetic resonance logging tool includes: a housing, a magnet and an antenna array apparatus; the magnet is fixedly arranged in the housing; the antenna array apparatus includes at least two groups of antenna arrays distributed along circumference of the magnet, and each group of antenna arrays include N layers of independently fed antennas; k-th layer antenna is arranged between the magnet and (k+1)-th layer antenna, k=1, 2, . . . N−1; the antenna is fixed on a support, and the support is fixedly connected to the housing. In the present invention, stratum information detection at different azimuth angles is achieved by exciting different antenna arrays, so that circumferential recognizing capability of nuclear magnetic resonance logging tool probe is improved and three-dimensional (radial, axial and circumferential) stratum detection is achieved.