Acoustic Transmitter Bender Bars for Anisotropic Logging
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Solution Overview
Problem
Existing acoustic logging tools face challenges in accurately interpreting data from anisotropic formations due to limited control over dipole orientation and generation of monopole frequencies, especially when the logging tool is eccentric in the borehole, leading to reduced data quality and increased logging time.
Innovation Solution
A transmitter design with four mutually orthogonally orientated bender bars that can be electrically driven to generate monopole or multi-pole pressure patterns, allowing for adjustable waveform types and orientations, including the ability to rotate poles by 45°, enhancing data redundancy and flexibility without increasing the number of hydrophones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional acoustic logging tools are used in anisotropic formations, then logging can be performed, but data interpretation accuracy deteriorates due to limited control over dipole orientation
Solution Approach 1:
The patent applies the dynamics principle by making the dipole orientation adjustable and controllable. The transmitter can generate dipole waves at different orientations (including 45° rotation capability) allowing adaptation to the specific anisotropic formation characteristics. This dynamic control enables optimal orientation selection for accurate data interpretation in varying geological conditions.
Solution Approach 2:
The patent implements parameter changes by varying the orientation angle of the dipole waves generated by the transmitter. The system can change the directional parameters of acoustic energy propagation to match the principal stress directions or fracture orientations in the formation, thereby improving measurement precision in anisotropic environments.
2Productivity
If the logging tool is positioned eccentrically in the borehole, then logging can continue, but data quality deteriorates
Solution Approach 1:
The patent addresses eccentric tool positioning by enabling parameter changes in the acoustic wave generation. The system can adjust the orientation and type of waves (monopole, dipole, quadrupole) to compensate for the asymmetric positioning, maintaining data quality despite the tool's off-center location in the borehole.
3Productivity
If monopole frequencies are generated with conventional tools, then logging data can be obtained, but frequency control is limited resulting in reduced logging efficiency
Solution Approach 1:
The patent applies dynamics by enabling flexible and adjustable frequency control for monopole wave generation. The transmitter can dynamically adjust the frequency parameters based on the specific logging requirements and formation characteristics, improving logging efficiency through optimized frequency selection rather than being constrained to fixed frequency ranges.
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 design improves data redundancy and flexibility, allowing for effective logging in anisotropic formations and eccentric tool conditions, with the ability to generate lower frequency monopole waves and adjust pole orientations, thereby enhancing logging efficiency and data quality.
Implementation Method 1
The bender bars include piezoelectric elements that may be energized under the influence of a control circuit to cause them to deflect in opposite directions and thereby generate a dipole wave
Implementation Method 2
acoustic (i.e. mechanical fluid wave) energy is generated by the logging tool and transmitted into the rock surrounding a borehole. The energy returned to the tool after passing through the rock is detected by one or more acoustic energy detectors
Data Source
AI summary
A transmitter for an acoustic logging tool includes an elongated housing, an acoustic energy generator, and a driver. The elongate housing defines a hollow interior and supports an acoustic energy generator, which includes four mutually orthogonally orientated bender bars that are electrically driveable to flex within the hollow interior in order to generate pressure-derived waves in a fluid surrounding the transmitter in use. The housing includes one or more transmissive windows via which flexing of the bender bars gives rise to propagation of one or more said waves in a said fluid. The driver electrically drives the bender bars to flex so as selectively to generate monopole, dipole, or quadrupole waves in a said fluid, with the poles of the dipole and quadrupole when generated selectively being aligned with normals to pairs of the bender bars or rotated 45° relative thereto.