Echo Detection in Noisy Downhole Logging via Time-Frequency Decomposition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Downhole ultrasonic measurement in oil-based mud environments faces challenges due to signal attenuation and noise interference, making it difficult to extract and identify echo signals effectively.
Innovation Solution
A system and method utilizing a digital signal processor to generate and shape firing pulses, segment and filter reflected waveforms, and perform time-frequency domain decomposition to separate echo signals from noise, allowing for accurate extraction of echo travel time and amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high voltage firing is used to boost response power, then the ultrasonic signal power is improved, but the system noise floor increases making echo detection harder
Solution Approach 1:
The patent segments the ultrasonic signal processing into multiple stages: signal generation, time-frequency decomposition, and echo detection. By dividing the reflected waveform into multiple segments and applying shaped filters to each, the system can process the high-power signal while managing noise through segmented analysis rather than treating it as a single overwhelming signal.
Solution Approach 2:
The patent transforms the signal from the time domain to the time-frequency domain using decomposition techniques. This dimensional transformation allows the system to analyze signals in both time and frequency simultaneously, separating echo signals from noise by their frequency characteristics even when they overlap in time, thus detecting echoes amidst high noise floors.
2Productivity
If heavy mud is used in the borehole, then drilling capability is improved, but ultrasonic signal attenuation increases significantly
Solution Approach 1:
The patent changes the parameters of the ultrasonic signal, specifically using high-frequency signals and adjusting the pulse duration and amplitude. By optimizing these parameters, the system compensates for the heavy mud attenuation and maintains sufficient signal strength for detection despite the energy loss in the drilling fluid.
Solution Approach 2:
The patent applies preliminary signal processing operations including shaped filtering and time-frequency decomposition before echo detection. These preliminary actions prepare the signal by enhancing useful frequency components and suppressing noise, making the subsequent echo detection more effective even after significant attenuation has occurred in the heavy mud environment.
3Measurement precision
If signal processing complexity is increased to separate echo from noise, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex hardware-based signal separation methods with software-based digital signal processing techniques. By using algorithms for time-frequency decomposition and shaped filtering implemented in software, the system achieves high measurement precision without requiring additional complex physical components or hardware systems.
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 enhances the detection of echo signals in noisy environments, improving the accuracy of borehole radius and acoustic impedance measurements, and enabling robust ultrasonic imaging.
Implementation Method 1
Piezo-based ultrasonic downhole measurement typically operates in a pitch-catch mode where a source pulse wave is generated by applying voltage on a Piezo transducer
Implementation Method 2
an ultrasonic signal may be heavily attenuated by the mud; typically, the heavier the mud, the greater the attenuation. The attenuation rate may be up to 30 ̃40 dB/inch for heavy mud cases
Implementation Method 3
The reflected waveforms (also called echo) are captured and recorded by the same or a different transducer
Data Source
AI summary
A method for echo detection may comprise recording one or more reflected waveforms, segmenting the one or more reflected waveforms based at least in part on a firing pulse length, applying a shaped filter to each segment of the one or more reflected waveforms, decoupling the one or more reflected waveforms into a time-frequency energy map, extracting a firing frequency band time domain plot from the decoupled time-frequency map, identifying a maximum amplitude in the extracted firing frequency band of the one or more reflected waveforms as an excitation, and identifying a second maximum amplitude in the extracted firing frequency band of the one or more reflected waveforms as an echo. A system for echo detection may comprise a digital signal processor, a transmitter, a transducer, a receiver, an analog to digital converter configured to digitize the measurement, and an information handling system.