Downhole Acoustic Sensor Backing with Reflective Cavity

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Solution Overview

Problem

Piezoelectric acoustic sensors used in oilfield services face challenges with signal attenuation and self-induced interference in high-density downhole fluid environments, leading to reduced accuracy and consistency due to decreased signal-to-noise ratio (SNR).

Innovation Solution

Incorporating a backing material layer with an acoustic reflector within the piezoelectric acoustic sensor, which includes an acoustic impedance discontinuity to reduce self-induced interference by reflecting and absorbing acoustic waves outside the echo response phase, thereby improving SNR.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If piezoelectric transducers are used to generate acoustic signals in high density downhole fluid environments, then acoustic measurement capability is provided, but signal attenuation occurs leading to reduced signal-to-noise ratio

Engineering Contradiction:

Improveacoustic measurement accuracyVSAvoidacoustic signal attenuation

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

An acoustic reflector is introduced as an intermediary element within the backing material layer to manage acoustic energy. The reflector has acoustic properties intermediate between the piezoelectric transducer and the outer environment, enabling controlled reflection and absorption of acoustic waves to reduce attenuation and improve signal quality.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If piezoelectric transducers generate acoustic signals, then measurement function is achieved, but self-induced acoustic interference degrades performance by reducing signal-to-noise ratio

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidself-induced acoustic interference

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The acoustic reflector converts the harmful self-induced acoustic interference into a beneficial effect by reflecting acoustic waves away from the transducer face. The interference that would normally degrade the signal is redirected to absorb at the reflector interface, transforming a harmful factor into a mechanism for improving signal-to-noise ratio.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Measurement precision

If acoustic waves propagate through drilling mud or downhole wellbore substances, then measurement data is obtained, but substantial attenuation reduces data accuracy and consistency

Engineering Contradiction:

Improvedata accuracy and consistencyVSAvoidacoustic signal energy loss

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The acoustic reflector performs preliminary action by intercepting and absorbing acoustic waves before they can propagate into the downhole environment and suffer substantial attenuation. By managing acoustic energy at the source interface, the system preserves signal integrity and prevents energy loss that would occur during propagation through attenuating media.

Inventive Principle:

Principle #10Preliminary action

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 effectively minimizes reverberation interference and enhances the accuracy and consistency of acoustic signal measurements by dissipating acoustic energy prior to the echo response phase, leading to improved signal quality and reduced noise.

Implementation Method 1

an acoustic reflector embedded within the backing material layer... configured to reduce self-induced interference by reflecting and absorbing acoustic waves

Methodology Applied

Scientific EffectAcoustic reflection: Reflection

Implementation Method 2

a backing material layer coupled to a back side of the piezoelectric transducer... configured to reduce self-induced interference by reflecting and absorbing acoustic waves

Methodology Applied

Scientific EffectAcoustic absorption: Acoustic Absorption

Implementation Method 3

The acoustic sensor comprises a piezoelectric transducer configured to periodically generate acoustic signals, such as ultrasonic pulses

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS11554387B2Ringdown controlled downhole transducer

Publication Date: 2023.01.17 HALLIBURTON ENERGY SERVICES INC

AI summary

An apparatus and system for deploying an acoustic sensor are disclosed. In some embodiments, an acoustic sensor includes a transducer comprising a piezoelectric material layer having a front side from which the transducer is configured to transmit acoustic sensing signals and an opposing back side. A backing material layer comprising an acoustic damping material is coupled at a front side to the back side of the piezoelectric material layer. An acoustic reflector such as may comprise a cavity containing gaseous or liquid fluid is disposed between the front side and a back side of the backing material layer.