Downhole Acoustic Mapping Tool Eccentering Compensation
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Solution Overview
Problem
Current downhole acoustic tools face inaccuracies in cement bonding quality assessment due to tool eccentering and limited spatial resolution, especially in azimuthally heterogeneous formations and cased-holes, where lower frequency ranges and axial measurements are insufficient for precise evaluation.
Innovation Solution
The implementation of a downhole tool with azimuthally distributed transmitters and receivers, operating at different frequency ranges (less than 30 kHz and greater than 50 kHz), allows for accurate detection of empty spaces within cement and improved cement bonding quality assessment by compensating for tool eccentering and providing higher spatial resolution through both axial and angle path measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If lower frequency acoustic signals (below 30 kHz) are used for cement bonding evaluation, then the tool can operate in a wider frequency range for formation elastic properties measurement, but the spatial resolution of the acoustic logging tool is limited
Solution Approach 1:
The patent divides the acoustic measurement system into two distinct frequency subsystems: a low-frequency subsystem (below 30 kHz) for formation elastic properties and a high-frequency subsystem (above 50 kHz) for cement bonding evaluation. Each subsystem has dedicated transmitters and receivers optimized for its frequency range, allowing both functions to operate simultaneously without interference and achieving both wide adaptability and high measurement precision.
2Measurement precision
If higher frequency acoustic signals (above 50 kHz) are used for cement bonding evaluation, then the spatial resolution is improved, but the impact of tool eccentering becomes larger
Solution Approach 1:
The patent employs an asymmetric azimuthal distribution of transmitters and receivers, with transmitters positioned at specific azimuthal locations and receivers distributed at different azimuthal positions. This asymmetric arrangement, combined with selective activation of transmitters based on tool orientation, compensates for eccentering effects by providing geometric correction capabilities while maintaining high-frequency spatial resolution.
Solution Approach 2:
The patent transitions from conventional axial-only measurements to three-dimensional azimuthal measurements by distributing transmitters and receivers around the tool circumference. This adds the azimuthal dimension to the measurement space, enabling detection and correction of eccentering effects through geometric relationships between multiple measurement paths.
3Measurement precision
If a single transmitter is placed on one side of the tool for azimuthally focused measurements, then the transmitter and receiver array can provide localized measurements, but the tool must be rotated to achieve full azimuthal coverage, which is not possible with wireline conveyance
Solution Approach 1:
The patent segments the transmitter system into multiple independently controllable transmitters distributed azimuthally around the tool. By selectively activating specific transmitters based on the desired measurement azimuth, the system achieves azimuthally focused measurements without requiring physical rotation of the tool, making it compatible with wireline conveyance methods.
4Device complexity
If conventional axial receiver arrays are used for cement bonding evaluation, then the tool structure is simple, but the azimuthal variation of cement bonding cannot be accurately evaluated
Solution Approach 1:
The patent uses asymmetric azimuthal distribution of receivers at multiple axial positions, with different numbers and positions of receivers at each axial location. This asymmetric configuration optimizes the measurement geometry for detecting azimuthal variations in cement bonding while maintaining a relatively simple tool structure.
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 approach enhances the accuracy and reliability of cement bonding quality evaluation by minimizing the effects of tool position and providing detailed azimuthal coverage without the need for rotational positioning, effectively addressing the limitations of existing technologies.
Implementation Method 1
A first transmitter unit of the downhole tool is located at a first axial location of the downhole tool and is operable to transmit a first acoustic signal at a first frequency that is less than 30 kilohertz
Implementation Method 2
A first receiver unit of the downhole tool is located at a second axial location axially offset from the first axial location, and is operable to measure amplitude of the first acoustic signal
Data Source
AI summary
A downhole tool for operation within a wellbore and including a transmitter array and first and second receiver arrays. The transmitter array includes a plurality of transmitters azimuthally distributed around a longitudinal axis of the downhole tool at a first axial location of the downhole tool. The first receiver array includes a plurality of first receivers azimuthally distributed around the longitudinal axis at a second axial location axially offset from the first axial location. The second receiver array includes a plurality of second receivers azimuthally distributed around the longitudinal axis at a third axial location axially offset from the first and second axial locations.