Echo-Peak Detection in Borehole Image Logging
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Solution Overview
Problem
Acoustic pulse-echo imaging tools face challenges in estimating the arrival times and amplitudes of overlapping, reverberatory reflections in borehole cement bonding quality assessment, due to complex signal processing requirements.
Innovation Solution
The method involves generating an acoustic pulse, receiving overlapping events, estimating the signal envelope, and determining arrival times using a Cauchy-Hilbert bandpass filter and Gaussian-Laplace operator to characterize cement bonding properties between the casing and earth formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional signal processing methods are used to detect overlapping reflections, then the measurement process becomes complex and computationally intensive, but the arrival time estimation accuracy deteriorates due to signal overlap and reverberation
Solution Approach 1:
The patent transforms the signal processing problem by changing the parameter domain from time-domain analysis to frequency-domain analysis using Hilbert transform. This parameter transformation allows the extraction of envelope characteristics that are insensitive to signal overlap and reverberation, thereby improving arrival time estimation accuracy without increasing processing complexity
Solution Approach 2:
The patent replaces conventional mechanical signal processing approaches (filtering, windowing, iterative deconvolution) with a mathematical field-based approach using Cauchy-Hilbert bandpass filtering. This substitution eliminates the need for complex iterative algorithms while maintaining or improving measurement precision
2Reliability
If the transducer emits acoustic pulses to detect cement bonding quality, then the detection capability is improved, but the reverberatory nature of the signal causes overlapping reflections that complicate analysis
Solution Approach 1:
The patent extracts the useful information (envelope characteristics and arrival times) from the complex reverberatory signal by applying Hilbert transform to obtain the analytic signal. This extraction process separates the amplitude modulation information from the carrier wave, effectively removing the harmful reverberation effects while preserving the diagnostic cement bonding information
Solution Approach 2:
The patent introduces the Hilbert transform as an intermediary mathematical operation between signal acquisition and analysis. This intermediary transformation creates an analytic signal that serves as a bridge, converting the difficult-to-analyze real signal into a form where envelope detection becomes straightforward and arrival time estimation becomes robust against overlapping reflections
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 effectively separates and identifies overlapping reflections, enabling accurate assessment of cement bonding quality, casing properties, and detecting defects within the cement annulus.
Implementation Method 1
The acoustic pulse-echo imaging tool usually comprises a rotating head on which is mounted a piezoelectric element transducer. The transducer periodically emits an acoustic energy pulse
Implementation Method 2
After emission of the acoustic energy pulse, the transducer can be connected to a receiving circuit for measuring a returning echo of the previously emitted acoustic pulse
Implementation Method 3
estimating an envelope of the received signal; and estimating from the envelope of the received signals an arrival time of each of the plurality of events
Data Source
AI summary
Signals from an acoustic transducer used in a borehole include overlapping, ringing reflections from the casing walls, voids in the cement and the formation. By using the Hilbert transform, an envelope of the signals is determined and individual echoes are detected by using a Gauss-Laplace operator.