Monopole Acoustic Transmitter With Nested Piezoelectric Disc Stack
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Acoustic logging systems face limitations in achieving optimal acoustic pressure and frequency output due to structural restrictions in logging-while-drilling (LWD) and measurement-while-drilling (MWD) tools, which affect the energy and frequency output of monopole acoustic transmitters.
Innovation Solution
A monopole acoustic transmitter comprising a stack of thin piezoelectric discs with central holes, held together under compressional force and electrically connected using conductive epoxy or copper shims, with end caps made of different materials to control pressure and frequency output, optimized for placement on the perimeter of the logging tool housing to maximize acoustic energy transmission into the borehole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the transmitter is disposed near the outer periphery of the tool to maximize acoustic energy transmission, then acoustic pressure output is improved, but the radial depth and azimuthal width of the recess are restricted by structural strength requirements
Solution Approach 1:
The transmitter assembly is nested within a recess in the outer surface of the drill collar, with the piezoelectric element positioned within the recess and covered by a protective cover that is also disposed within the recess. This nesting arrangement allows the transmitter to be positioned near the outer periphery for maximum acoustic energy transmission while maintaining the structural integrity of the drill collar by not compromising its radial depth and azimuthal width.
2Power
If the transmitter dimensions are increased to maximize acoustic energy output, then energy transmission is improved, but the space required for fastening, sealing, and mechanical isolation increases
Solution Approach 1:
The transmitter assembly including the piezoelectric element, end caps, and protective cover is nested within a recess in the drill collar. This integration eliminates the need for separate fastening, sealing, and isolation structures that would otherwise be required, reducing the additional space needed while maintaining the transmitter's acoustic energy output capabilities.
3Device complexity
If a single piezoelectric element is used to simplify the transmitter structure, then device complexity is reduced, but sufficient energy at the desired frequency cannot be obtained
Solution Approach 1:
The transmitter uses a stack of multiple thin piezoelectric discs instead of a single piezoelectric element. Each disc is electrically connected in series or parallel configuration, and when voltage is applied, all discs expand or contract simultaneously to generate acoustic energy. This segmentation allows the transmitter to produce sufficient energy at the desired frequency while maintaining a relatively simple overall structure that can be accommodated within the drill collar recess.
4Power
If the recess dimensions are increased to accommodate larger transmitter, then acoustic pressure output is improved, but structural strength of the drill collar is compromised
Solution Approach 1:
The transmitter assembly is nested within a recess that has controlled dimensions, with the piezoelectric element positioned within the recess and covered by a protective cover. This nesting arrangement allows the transmitter to be positioned optimally for acoustic pressure output while the recess dimensions are kept minimal to preserve the structural strength of the drill collar.
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
The solution enhances acoustic pressure output and frequency precision, allowing for more accurate measurement of formation parameters while meeting structural and operational requirements of LWD and MWD systems, ensuring effective energy transmission and minimizing tool mode signals.
Implementation Method 1
If the transmitter comprises piezoelectric transducers, the acoustic pressure output of an acoustic transmitter is proportional to the dimensions and the configuration of the transmitter
Implementation Method 2
The frequency output and the acoustic energy output of a piezoelectric element are both a function of the geometry and dimensions of the piezoelectric element
Data Source
AI summary
A monopole acoustic transmitter with at least one disc assembly with a plurality of piezoelectric discs configured to optimized acoustic pressure output within a desired frequency range while meeting physical restrictions of LWD and MWD logging systems. The transmitter is disposed in a recess or “slot” in the perimeter of a logging tool housing to reduce acoustic pressure waves transmitted directly along the tool housing and to optimize acoustic energy transmission into the borehole environs. In order to increase acoustic pressure output at a desired logging frequency range, the plurality of piezoelectric discs in each of at least one disc assembly are connected electrically in parallel and fired simultaneously. The polarity of the discs and the wiring arrangement are such that each disc expands or contracts in a common direction during simultaneous firing by an applied voltage. The desired output frequency is obtained by selectively polarizing and dimensioning the discs within the one or more disc assemblies. Each disc assembly is preferably disposed within an oil filled pressure housing that is pressure and temperature compensated. The axis of the at least one disc assembly can be parallel or perpendicular to the major axis of the logging tool.