Spectral Noise Logging Tool for Casing Leak Detection
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Solution Overview
Problem
Current acoustic noise logging methods in hydrocarbon exploration have limitations in detecting fluid flow through or behind well casings due to coarse frequency resolution and inability to separate noise from well completion leaks and surrounding formations, restricting the detection of leaks with lower flow rates and failing to identify completion elements effectively.
Innovation Solution
A spectral noise logging method and tool that record power-frequency spectrum data at multiple stationary positions within a borehole, processing these data sets to generate a spectral noise log, using an acoustic detector with multiple frequency channels and digital signal processing to achieve high sensitivity and frequency resolution from 8 Hz to 60 kHz, allowing for the detection and characterization of fluid flow through or behind the casing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If coarse frequency resolution and time averaging are employed, then high flow rate leaks can be detected, but detection sensitivity for lower flow rates is insufficient and noise from different sources cannot be separated
Solution Approach 1:
The acoustic spectrum is segmented into multiple frequency bands (e.g., 20-100 Hz, 100-500 Hz, 500-2000 Hz, 2000-6000 Hz, 6000-12000 Hz, and above 12000 Hz) using band-pass filters. This segmentation allows different frequency ranges to be analyzed independently, enabling differentiation between various noise sources and improving detection sensitivity for lower flow rate leaks without requiring overly complex high-resolution frequency analysis across the entire spectrum.
Solution Approach 2:
The patent transitions from time-domain analysis to frequency-domain analysis by employing spectrum analyzers for each frequency band. This dimensional transformation allows the system to characterize leaks based on their spectral signatures rather than just temporal patterns, enabling separation of noise from different sources (casing leaks vs. formation noise) and improving detection of lower flow rates through spectral fingerprinting.
2Measurement precision
If single frequency band analysis is used, then the system is simpler, but inability to separate acoustic noise from well completion leaks and formation noise limits detection accuracy
Solution Approach 1:
The acoustic spectrum is segmented into multiple frequency bands (e.g., 20-100 Hz, 100-500 Hz, 500-2000 Hz, 2000-6000 Hz, 6000-12000 Hz, and above 12000 Hz) using band-pass filters. This segmentation allows different frequency ranges to be analyzed independently, enabling differentiation between various noise sources and improving detection sensitivity for lower flow rate leaks without requiring overly complex high-resolution frequency analysis across the entire spectrum.
Solution Approach 2:
The patent transitions from time-domain analysis to frequency-domain analysis by employing spectrum analyzers for each frequency band. This dimensional transformation allows the system to characterize leaks based on their spectral signatures rather than just temporal patterns, enabling separation of noise from different sources (casing leaks vs. formation noise) and improving detection of lower flow rates through spectral fingerprinting.
3Measurement precision
If continuous logging process is employed, then productivity is improved, but road noise from tool bumping and scraping increases measurement noise
Solution Approach 1:
The system employs periodic measurement cycles where the tool is moved to a new position, allowed to stabilize for a predetermined period, and then measurements are taken. This periodic approach with stabilization periods allows road noise from tool movement to subside before data collection, improving signal-to-noise ratio while maintaining reasonable logging productivity through efficient use of measurement windows.
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 method and tool provide improved detection and characterization of fluid flow, enabling the identification of leaks and fluid types, flow rates, and rock types, with increased sensitivity and accuracy over existing systems, capable of detecting noise generated behind the casing and within the surrounding formation.
Implementation Method 1
detecting an acoustic noise within a first frequency range; additionally detecting an acoustic noise within a second frequency range
Implementation Method 2
The acoustic detector comprises a pressure pulse sensor or hydrophone. The hydrophone comprises a piezo electric transducer
Data Source
AI summary
In the present invention that considerable advantage is to be gained in the provision of apparatus and methods for spectral noise logging that exhibit improved frequency resolution and thus sensitivity over those systems known in the art since this would allow for improved detection and characterization of fluid flow through, or behind, a casing of a well penetrating subsurface formations.