Annular Eccentricity Estimation via Pulse-Echo Waveform Coherence
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Solution Overview
Problem
Current methods for determining the eccentricity and orientation of inner tubulars in dual-string cased wells are limited by the inability to accurately measure compressional wave propagation speed in high-density cement, which affects the reliability of cement evaluation and plugging and abandonment operations.
Innovation Solution
The use of pulse-echo signals to estimate inner tubular eccentricity and compressional wave propagation speed in the annular material, allowing for waveform-by-waveform processing and coherence computation to compensate for outer casing eccentricity, thereby enhancing the accuracy of cement evaluation and material identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to determine inner tubular eccentricity, then the process is simpler, but the measurement precision deteriorates due to inability to accurately measure compressional wave propagation speed in high-density cement
Solution Approach 1:
The patent applies preliminary action by performing waveform-by-waveform processing and coherence computation before final eccentricity calculation. The system pre-processes pulse-echo signals to compensate for outer casing eccentricity effects, establishing accurate reference waveforms that enable subsequent precise measurement of compressional wave propagation speed in high-density cement without requiring complex post-processing corrections
Solution Approach 2:
The patent uses coherence computation as an intermediary technique to bridge the gap between raw pulse-echo signals and accurate eccentricity measurements. By computing coherence between reference and measured waveforms, the system isolates the effect of inner tubular eccentricity from other factors, enabling precise measurement of wave propagation speed even in challenging high-density cement conditions
2Measurement precision
If waveform-by-waveform processing with coherence computation is applied, then measurement precision improves, but processing time increases
Solution Approach 1:
The patent applies partial action by selectively processing only the necessary waveform components for eccentricity determination. Rather than performing exhaustive analysis on entire signal sequences, the system focuses coherence computation on specific time windows and frequency bands that contain the relevant eccentricity information, achieving accurate measurements with reduced processing time
3Reliability
If outer casing eccentricity is not compensated, then processing is simpler, but reliability of cement evaluation deteriorates
Solution Approach 1:
The patent extracts and isolates the outer casing eccentricity effect from the total signal using coherence computation. By separating this interfering component, the system can compensate for it explicitly in the eccentricity calculation, ensuring reliable cement evaluation without requiring complete redesign of the measurement system
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 provides robust and accurate estimation of inner tubular eccentricity and compressional wave propagation speed, improving the quality of cement evaluation and enabling reliable identification of annular material types, even in high-density cement conditions.
Implementation Method 1
acoustic waves are emitted by the pulse-echo tool and propagate in the annular material between the inner tubular and the outer casing
Implementation Method 2
acquired pulse-echo signals in a dual-string cased hole
Data Source
AI summary
Determining eccentricity and its direction of an inner tubular (e.g., tubing, liner, inner casing, etc.) in a cased hole using pulse-echo signals that are acquired in, for example, a dual-string cased well, being pre-processed for enhancing echo signals from the outer annular boundary and for reducing the inner tubular specular echo and pipe ringing. Disclosed methods also provide propagation speeds, of the signals traversing the annular materials between the inner tubular and outer annular boundary, that is be used to identify annular material (e.g., production fluids, brine, water, cement, collapsed formation, etc) and one of the input parameters for dual-string cement evaluation.