Sonic Phase Slowness Dispersion Analysis for Multi-String Well Integrity
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Solution Overview
Problem
Current methods for diagnosing well zonal isolation, particularly in multi-string casing configurations, face challenges in effectively probing and analyzing cement placement and bond conditions beyond the first casing and annulus, due to increased complexity and limitations in computational resources for continuous logging over thousands of feet.
Innovation Solution
The use of sonic data from monopole, dipole, and quadrupole modalities to process phase slowness dispersions, generate plots of slowness, attenuation, and wavenumber projections, and match these with templates derived from modeling scenarios of free pipes in multiple casing string configurations to diagnose the integrity of dual and multi-string casings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If sonic measurements are used to diagnose cement placement and bond conditions beyond the first casing in multi-string configurations, then the depth of probing and diagnostic capability are improved, but the complexity of measurement physics and data analysis increases significantly
Solution Approach 1:
The patent segments the complex multi-casing diagnostic problem into distinct analytical components: (1) processing sonic measurements to identify cut-off modes for each casing, (2) determining free pipe intervals for inner and outer casings separately, (3) analyzing annulus content based on mode identification, and (4) generating depth-dependent diagnostic results. This segmentation allows the system to handle the complexity of multiple casings by treating each casing's acoustic signature independently while integrating results.
Solution Approach 2:
The patent transforms the diagnostic approach by adding the dimension of frequency analysis through cut-off mode identification. Instead of relying solely on traditional amplitude-based sonic logging, the system analyzes the frequency-dependent behavior of acoustic waves to identify characteristic cut-off modes that indicate free pipe conditions. This dimensional transformation from spatial-only to frequency-spatial joint analysis enables deeper probing through multiple casings.
2Length of stationary object
If continuous sonic logging is performed over thousands of feet to cover the entire well, then the coverage and diagnostic completeness are improved, but the computational resources required become prohibitive
Solution Approach 1:
The patent extracts and focuses on specific diagnostic features from the continuous sonic logging data, namely the cut-off modes and their frequency characteristics. Rather than processing and analyzing all sonic measurement data in detail over thousands of feet, the system identifies and extracts the key indicators of well integrity (cut-off mode presence, frequency, and attenuation) that are sufficient to diagnose annulus content and casing integrity. This extraction approach maintains comprehensive coverage while reducing computational burden.
Solution Approach 2:
The patent applies partial action by performing detailed cut-off mode analysis only at depth intervals where diagnostic information is most critical, such as transitions between cemented and uncemented zones. The system processes continuous logging data but applies full analytical rigor selectively, using simplified identification methods in stable intervals and more detailed analysis at transition zones, thereby optimizing computational resource usage across the entire well depth.
3Measurement precision
If traditional low frequency sonic logging tools are used for cement evaluation, then the measurement capability for single casing is sufficient, but the ability to diagnose cement behind multiple casings is limited
Solution Approach 1:
The patent enhances the universality of sonic logging tools by developing a diagnostic system that can evaluate multiple casing configurations using the same measurement platform. The system processes sonic measurements to identify cut-off modes characteristic of different casing-annulus-formation configurations, enabling a single tool to diagnose both single and multi-casing wells. The methodology universally applies to various well architectures by adapting the interpretation of cut-off mode patterns rather than requiring different hardware for different configurations.
Solution Approach 2:
The patent employs a composite diagnostic approach that combines multiple acoustic modalities (different sonic measurement types and frequencies) to achieve diagnostic capability for multi-casing configurations. By integrating analysis of various acoustic wave behaviors and their interactions with multiple casings, the system creates a composite diagnostic model that leverages the strengths of different measurement approaches to penetrate and characterize complex multi-casing structures that traditional single-modality tools cannot resolve.
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 allows for a more robust diagnosis of well integrity by identifying depth-dependent changes and discontinuities, enabling accurate assessment of cement placement and bond conditions across multiple casings, thereby improving the reliability of well integrity evaluation.
Implementation Method 1
A sonic tool 10 includes a plurality of sonic sources 20 and a plurality of spaced sonic detectors 30. The sonic sources may be referred to as transmitters and the detectors as receivers.
Implementation Method 2
measured dispersions with one or more template cut-off modes is an indicator of the corresponding scenario in the multi-string configuration
Data Source
AI summary
Methods arc provided for using sonic tool data to investigate a multi-string wcllbore. The sonic data is processed to obtain indications of phase slowness dispersions for multiple locations in the wellbore. The dispersions are aggregated. The aggregated dispersions are compared with a plurality of cut-off mode templates to identify the presence of cut-off modes or the lack thereof in the aggregated phase slowness dispersions. Features of the multi-string wellbore are identified based on the presence of the cut-off modes or the lack thereof. In another method, the sonic data is processed to obtain indications as a function of depth of at least one of an energy spectrum, a semblance projection, a slowness dispersion projection, an attenuation dispersion projection, and a wavenumber dispersion projection. The indications are inspected to locate a shift at a particular depth indicat- ing a transition in at least oneannulus of the multi-string wellbore.