Rotating Eccentric Mass Acoustic Source for Borehole Flexural Waves
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Solution Overview
Problem
Conventional sonic tools have a limited ability to generate strong low-frequency flexural waves in geological formations, requiring large amounts of power and facing challenges in fabricating acoustic wave generation elements, such as piezoelectric crystals, that operate to produce well-matched dipole sources.
Innovation Solution
A mechanical system driven by a motor and transmission is used to generate multi-polar acoustic emissions, with a cam-driven piston producing repetitive acoustic pulses, allowing for controlled amplitude and spectral content of the acoustic waves by varying the cam shape and motor speed, enabling consistent production of strong flexural waves in boreholes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional piezoelectric and electromagnetic sources are used, then acoustic energy can be generated, but large amounts of power are required and the ability to generate strong low frequency flexural waves is limited
Solution Approach 1:
The patent replaces conventional piezoelectric and electromagnetic sources with a mechanical vibration source consisting of an eccentric mass rotating within a borehole. This mechanical system generates acoustic waves through centrifugal force and direct mechanical coupling with the formation, eliminating the need for high-power electrical sources while effectively generating strong low-frequency flexural waves
Solution Approach 2:
The invention utilizes mechanical vibration of an eccentric mass rotating at controlled speeds to generate acoustic waves. The rotating eccentric mass creates periodic mechanical disturbances that couple with the borehole and formation, producing strong low-frequency flexural waves with adjustable frequency content based on rotation speed
2Ease of manufacture
If piezoelectric crystals are used to generate acoustic waves, then dipole sources can be produced, but the fabrication of well-matched dipole sources is difficult
Solution Approach 1:
The patent replaces complex piezoelectric crystal assemblies with a simple mechanical eccentric mass system. The dipole source characteristics are achieved through the geometric configuration of the eccentric mass and its rotation axis, which can be manufactured using standard machining techniques without requiring precise crystal orientation or complex assembly procedures
Solution Approach 2:
The invention allows adjustment of acoustic source characteristics by changing operational parameters such as rotation speed and eccentricity distance, rather than requiring precise manufacturing tolerances. This enables flexible tuning of dipole source properties after manufacture, simplifying the fabrication process while maintaining manufacturing precision
3Reliability
If conventional sonic tools are used, then measurements can be made in boreholes, but the ability to generate strong low frequency flexural waves is limited
Solution Approach 1:
The rotating eccentric mass generates strong low-frequency mechanical vibrations that directly couple with the borehole wall and formation. This mechanical vibration approach is particularly effective at low frequencies where conventional electromagnetic sources struggle, enabling reliable measurement of formation properties through enhanced flexural wave generation
Solution Approach 2:
The borehole fluid and borehole wall act as intermediaries that couple the mechanical vibration source to the formation. The rotating eccentric mass transfers energy through the borehole medium to the formation, effectively generating strong flexural waves that propagate into the subsurface for reliable geological characterization
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 efficiently generates strong flexural waves in boreholes, enhancing the ability to characterize geological formations with improved acoustic energy output and reduced power requirements, thereby aiding in oil and gas exploration.
Implementation Method 1
a rotatable driving member having at least one driving lobe, and a unitary driven member having at least one cam. The driven member is configured to be set in motion to launch acoustic waves, including a dipole acoustic wave, along an axis substantially orthogonal to an axis of rotation of the driving member when the driving member rotates to periodically contact the cam with the driving lobe
Implementation Method 2
The acoustic wave has a signature at least partially determined by a profile of the cam and a rotation rate of the driving member
Data Source
AI summary
In some embodiments, an apparatus and a system, as well as a method and an article, may operate to rotate a rotatable driving member having at least one driving lobe, and to periodically contact at least one cam on a unitary driven member with the at least one driving lobe during rotation of the rotatable driving member, to set the driven member in motion. This motion can be used to launch an acoustic wave along an axis substantially orthogonal to the axis of rotation of the driving member, where the driving member disposed completely within the driven member. The signature of the acoustic wave can be at least partially determined by the profile of the cam and the rotation rate of the driving member. Additional apparatus, systems, and methods are disclosed.