Acoustic Logging Tool Coherent Noise Reduction
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Solution Overview
Problem
Recent developments in well drilling, such as heavier drilling fluids and lighter cements, reduce the effectiveness of acoustic logging tools in determining cement quality due to signal attenuation, introducing additional noise from tool electronics and transducer intrinsic noise.
Innovation Solution
An acoustic logging tool system that includes a transducer configured to emit and measure acoustic pulses in specific directions to isolate and remove coherent noise from measurements, using a data processing system to subtract noise components from echo signals, thereby improving the accuracy of cement quality assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the operating frequency of acoustic logging tools is reduced to account for signal attenuation from heavier drilling fluids and thicker casings, then the acoustic signal strength is improved, but additional noise is introduced due to acoustic tool electronics and transducer intrinsic noise
Solution Approach 1:
The system performs preliminary measurements at a location without the target acoustic surface to characterize the noise component before the actual measurement. This preliminary action allows the noise to be quantified and subsequently removed from the measurement signal, resolving the contradiction between using lower frequencies for better signal penetration and avoiding electronic noise.
Solution Approach 2:
The invention extracts and removes the noise component from the measurement signal by measuring the noise separately at a location without the acoustic surface and then subtracting it from the full measurement. This separation allows the useful signal to be isolated from the harmful noise, enabling the use of lower frequencies without being overwhelmed by electronic noise.
2Device complexity
If the transducer is used for both excitation and measurement to simplify the system, then device complexity is reduced, but coherent noise from the transducer itself is introduced into the measurement
Solution Approach 1:
The system performs a preliminary measurement at a location without the acoustic surface to capture the transducer's intrinsic noise and electronic interference. This preliminary characterization allows the transducer to be used for both excitation and measurement while its noise contribution is subsequently removed through signal processing, maintaining simplicity without sacrificing measurement quality.
Solution Approach 2:
The invention converts the harmful coherent noise from the transducer into a useful measurement by measuring the noise at a location without the acoustic surface. This allows the noise to be quantified and subtracted from the full measurement, transforming the transducer's intrinsic noise from a contaminant into a characterizable parameter that can be removed.
3Strength
If heavier drilling fluids and thicker casings are used in well construction, then wellbore strength and zonal isolation are improved, but acoustic signal attenuation increases
Solution Approach 1:
The system changes the operating frequency parameter to a lower value to compensate for the increased signal attenuation caused by heavier drilling fluids and thicker casings. This parameter adjustment allows the acoustic signal to penetrate through the more substantial wellbore construction while maintaining adequate signal strength for accurate measurements.
Solution Approach 2:
The invention uses feedback from preliminary measurements to characterize and remove noise components from the final measurement. This feedback mechanism allows the system to maintain measurement accuracy even when using lower frequencies that are more susceptible to attenuation, effectively compensating for the signal loss.
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
Enhances the accuracy of cement quality evaluation by effectively filtering out coherent noise, allowing for precise determination of solid, liquid, or gas characteristics behind the casing, even in challenging drilling conditions.
Implementation Method 1
the transducer is configured to emit a first acoustic pulse from the transducer in a first direction toward a first acoustic surface
Implementation Method 2
the first echo component is due at least in part to an interaction of the first acoustic pulse with the first acoustic surface
Data Source
AI summary
A system includes an acoustic logging tool including a transducer configured to: emit a first acoustic pulse in a first direction toward a first acoustic surface; measure a first acoustic signal, wherein the first acoustic signal includes a coherent noise component and a first echo component, wherein the first echo component is due at least in part to an interaction of the first acoustic pulse with the first acoustic surface; emit a second acoustic pulse in a second direction, wherein the second direction is at least partly directed away from the first acoustic surface; and measure a second acoustic signal, wherein the second acoustic signal includes substantially only the coherent noise component. The system also includes a data processing system that includes a processor configured to remove the measurement of the second acoustic signal from the measurement of the first acoustic signal to reduce coherent noise.