NMR Logging Tool Antenna Configuration for Vertical Resolution
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Solution Overview
Problem
Current well logging technologies face challenges in achieving high-resolution borehole measurements, particularly in reconciling horizontal and vertical resistivity measurements in inhomogeneous reservoirs, leading to inaccurate hydrocarbon saturation estimates due to limitations in signal strength, thermal noise, and relaxation time constraints.
Innovation Solution
The development of a nuclear magnetic resonance (NMR) logging tool with a novel antenna configuration that includes quadrature-driven solenoids and multiple receive antennas, allowing for higher bandwidth and signal-to-noise ratio, enabling improved vertical resolution and independence from borehole angle and rugosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a longer antenna is used to improve signal strength, then signal-to-noise ratio improves, but vertical resolution deteriorates
Solution Approach 1:
The antenna system is divided into multiple discrete antenna elements (at least two antennas) that can be independently controlled and processed. This segmentation allows the system to achieve both good signal strength through coherent stacking and high vertical resolution through the spatial distribution of antenna elements, resolving the contradiction between signal strength and resolution.
Solution Approach 2:
The patent introduces a new dimension of control by enabling independent phase and amplitude control of each antenna element. This multi-dimensional control space allows the system to optimize both signal strength (through coherent signal combining) and vertical resolution (through spatial frequency analysis), eliminating the traditional trade-off.
2Productivity
If logging speed is increased to improve productivity, then measurement time decreases, but signal strength deteriorates due to reduced stacking time
Solution Approach 1:
The system enables continuous measurement and processing during the logging operation by using multiple antenna elements that can continuously acquire data. The coherent stacking process continues without interruption, maintaining signal strength even at higher logging speeds where traditional single-antenna systems would require longer stacking times.
Solution Approach 2:
The system performs preliminary signal processing and stacking operations during the logging process itself, rather than requiring separate post-processing time. This preliminary action allows the signal to be fully processed while the tool is moving, maintaining signal strength at increased logging speeds.
3Measurement precision
If multiple antenna elements are added to improve vertical resolution, then measurement precision improves, but device complexity increases
Solution Approach 1:
The multiple antenna elements serve multiple functions simultaneously: they act as both transmit and receive antennas, provide spatial sampling for vertical resolution, and enable coherent stacking for signal strength. This multi-functionality reduces the need for separate components, thereby managing complexity while achieving high resolution.
Solution Approach 2:
The patent combines multiple antenna elements into an integrated array that operates as a unified system. The antennas are merged with the tool structure and control electronics, creating a cohesive NMR logging tool where the multi-antenna system is managed as a single functional unit rather than separate components, reducing overall system 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
This solution enhances the resolution of NMR measurements to match or exceed induction log resolution, providing more accurate hydrocarbon saturation and permeability estimates, and enabling real-time modeling of induction responses, thereby improving the understanding of formation properties and producability.
Implementation Method 1
a solenoid having a magnetic moment in a first direction and a solenoid having a magnetic moment in a second direction orthogonal to the first direction
Implementation Method 2
nuclear magnetic resonance (NMR) logging tool with a novel antenna configuration that includes quadrature-driven solenoids and multiple receive antennas
Data Source
AI summary
A nuclear magnetic resonance well logging tool, where some embodiments comprise two, oppositely oriented magnets separated by a pole piece to guide static magnetic flux into a sensitive volume, and another pole piece serving as a core for several antennas. For some embodiments, the antennas are solenoids. Two of the antennas serve as transmit and receive antennas, where they are driven to generate an elliptically polarized magnetic field, and their antenna responses are combined so that the combined response is sensitive to elliptically polarized magnetic fields, but with zero gradient in the z-direction. A third antenna serves as a receive antenna sensitive to magnetic field vectors having a sinusoidal spatial variation in the z-direction of period equal to the length of the third antenna. A fourth antenna serves as a receive antenna sensitive to sinusoidal magnetic field vectors with the same spatial-frequency as the third antenna, but phase shifted by 90 degrees. A fifth antenna may be utilized, which serves as a receive antenna sensitive to the next higher spatial-frequency component of the received signal. The receive antennas have good cancellation of mutual coupling. Other embodiments are described and claimed.