Dielectric Logging Tool Antenna Configuration for Standoff Compensation
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Solution Overview
Problem
Existing dielectric logging tools face limitations in accuracy and operating range due to hostile drilling environments and tool standoff effects, which affect the reliability of formation property measurements.
Innovation Solution
The use of three or more receive horn antennas positioned between two transmit antennas allows for absolute amplitude and phase measurements, extending the operating range and increasing measurement accuracy, and compensating for tool standoff and mudcake effects, enabling more precise logging of formation permittivity, conductivity, and standoff distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional dielectric logging tools are used in hostile drilling environments, then basic formation measurements can be obtained, but measurement accuracy and operating range are limited due to tool standoff effects and mudcake interference
Solution Approach 1:
The tool uses multiple transmit antennas and multiple receive antennas instead of single antennas, segmenting the measurement function across multiple elements. This allows for differential measurements that can cancel out standoff and mudcake effects, improving measurement accuracy in hostile environments
Solution Approach 2:
The system performs measurements at multiple frequencies and uses iterative inversion algorithms that incorporate feedback from the measured data to refine formation property estimates. The multiple antenna measurements provide redundant information that feeds into the inversion process to compensate for environmental effects
2Measurement precision
If single frequency or limited frequency range measurements are used, then tool complexity is reduced, but the ability to determine both resistivity and dielectric constant accurately is compromised
Solution Approach 1:
The system measures electromagnetic wave propagation at multiple frequencies rather than a single frequency. By changing the frequency parameter and measuring the complex propagation constant at each frequency, the system can separately determine both formation resistivity and dielectric constant with improved accuracy
Solution Approach 2:
The multi-frequency measurement system serves multiple functions: determining resistivity, determining dielectric constant, characterizing fluid properties, and compensating for environmental effects. This universal approach allows a single tool to perform multiple formation evaluation functions
3Productivity
If two transmit antennas and two receive antennas are used for basic measurements, then some formation properties can be measured, but the dynamic range and investigation depth are insufficient
Solution Approach 1:
The antenna array is segmented into multiple transmit elements and multiple receive elements, creating multiple measurement paths through the formation. This segmentation provides redundant measurements that improve reliability and extend the dynamic range of measurable formation properties
Solution Approach 2:
The system adds spatial dimensionality by using multiple antennas at different positions and orientations. This dimensional expansion from single-point to multi-point measurements provides additional independent measurements that improve both productivity and reliability
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 configuration provides improved measurement accuracy and depth investigation capabilities, enhancing the ability to log water-saturated porosity and oil movability, and extends the dynamic range and investigation depth beyond existing tools.
Implementation Method 1
dielectric tools determine the dielectric constant and conductivity of downhole formations from the real and imaginary parts of the complex propagation constant of electromagnetic waves traveling through the formations
Data Source
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AI summary
Disclosed dielectric logging tools and methods employ three or more receive horn antennas positioned between at least two transmit antennas, which can also be horn antennas. The logging tools can operate in the range between 100 MHz and 10 GHz to provide logs of formation permittivity, formation conductivity, standoff distance, and electrical properties of material in the standoff gap. Logs of water-saturated porosity and/or oil movability can be readily derived. The presence of additional receive antennas offers a significantly extended operating range, additional depths of investigation, increased measurement accuracy, and further offers compensation for tool standoff and mudcake effects. In both wireline and logging while drilling embodiments, at least some disclosed dielectric logging tools employ a set of three axially- spaced receive antennas positioned between pairs of axially- spaced transmit antennas. At least some disclosed methods employ absolute amplitude and phase measurements in response to alternate firings of the transmit antennas.