Acoustic Logging Tool Leak Localization via Eigenvalue Analysis
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Solution Overview
Problem
Existing methods for monitoring well integrity in oil or gas wells are limited in accuracy and precision for localizing underground fluid flows and leaks, which can lead to safety issues and environmental hazards.
Innovation Solution
An acoustic logging tool with a sensor array that acquires broadband acoustic signals and computes covariance matrices to determine the depth of acoustic sources using eigenvalues, enhancing the localization of leaks by correlating signals from multiple sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing acoustic detection methods are used to monitor well integrity, then leaks can be detected, but the accuracy and precision of leak localization is very limited
Solution Approach 1:
The wellbore is divided into discrete depth segments along the acoustic logging tool's path. The sensor array processes acoustic signals segment by segment, calculating leak probability for each depth interval. This segmentation allows precise localization of leaks to specific depth ranges while managing computational complexity through systematic processing of divided sections.
Solution Approach 2:
The patent transitions from traditional single-sensor or simple multi-sensor acoustic detection to a sophisticated multi-dimensional analysis approach. By deploying an array of acoustic sensors and processing signals across multiple dimensions (time, frequency, spatial distribution), the system achieves high-precision leak localization. The covariance matrix analysis and eigenvalue decomposition add mathematical dimensions to the signal processing, enabling accurate source positioning.
2Measurement precision
If acoustic signals from multiple sensors are correlated using covariance matrices and eigenvalues, then leak localization accuracy improves significantly, but computational complexity increases
Solution Approach 1:
The patent replaces traditional mechanical or simple electronic acoustic detection methods with advanced mathematical signal processing. Instead of relying on basic sensor outputs, the system uses covariance matrix computation and eigenvalue decomposition to extract precise leak location information. This substitution of mathematical algorithms for simpler detection methods enables high-precision localization while the systematic approach manages computational requirements.
Solution Approach 2:
The patent creates multiple virtual representations of the acoustic signals through covariance matrix computations. By generating eigenvalues and eigenvecs that represent different aspects of the acoustic field, the system processes the original signals through multiple mathematical copies. This allows comprehensive analysis of acoustic sources from different perspectives, improving localization accuracy while organizing computational work into manageable steps.
3Measurement precision
If a sensor array is deployed along the wellbore to improve leak detection precision, then localization accuracy increases, but the complexity of the detection system increases
Solution Approach 1:
The acoustic logging tool with sensor array serves multiple functions: detecting leaks, characterizing underground flows, and localizing acoustic sources. The same sensor array and processing system handle various detection tasks along the wellbore, making the system universally applicable to different monitoring needs. This multi-functionality justifies the increased complexity by providing comprehensive well integrity assessment capabilities.
Solution Approach 2:
The sensor array system processes its own acquired signals autonomously through the covariance matrix and eigenvalue analysis. The system self-determines leak locations and characteristics without requiring external intervention or additional complex equipment. The acoustic logging tool independently completes the full detection and localization process, making the increased device complexity self-justifying through autonomous operation.
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 significantly improves the accuracy and precision of leak detection and localization, allowing for safer well operation and better reservoir characterization.
Implementation Method 1
Monitoring downhole flows around wellbores, such as injected water, can further be of interest in reservoir characterization. Underground flows generally emit acoustic signals that can be measured, e.g., with fiber cables disposed along the wellbore or with acoustic point sensors such as Fiber Bragg Grating (FBG) sensors or hydrophones.
Implementation Method 2
correlating the acoustic signals acquired by the sensors in the frequency domain, e.g., by computing covariance matrices from the acoustic signals for each of a plurality of frequency bins within a frequency range covered by the broadband acoustic signals
Implementation Method 3
computing eigenvalues of the covariance matrices; and determining a depth along the wellbore of an acoustic source based on the eigenvalues computed for the plurality of frequency bins and the plurality of depths
Data Source
AI summary
Disclosed are acoustic logging systems and methods that involve correlating broadband acoustic signals acquired by a plurality of acoustic sensors at multiple depths within a wellbore to compute covariance matrices and their eigenvalues in the frequency domain for a plurality of frequency bins. In accordance with various embodiments, acoustic sources are detected and located based on the eigenvalues viewed as a function of depth and frequency.