Nested Casing Evaluation Using Inversion-Based Eddy Current Sensing
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Solution Overview
Problem
Existing methods for well casing integrity evaluation, such as degassing and liquid analysis, are unreliable due to unknown gas amounts and phase volumetric measurements, while EM logging tools face challenges with ghost events and complexities in mapping casing defects accurately.
Innovation Solution
Inversion-based methods using combined collocated and non-collocated sensor data processing, including time-domain and multi-frequency measurements, to determine casing thickness and identify defects in up to six nested casings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If degassing and liquid analysis methods are used for casing integrity evaluation, then dissolved gas detection is possible, but measurement reliability deteriorates due to unknown gas amounts and phase volumetric measurements
Solution Approach 1:
The patent replaces mechanical/chemical analysis methods (degassing and liquid analysis) with electromagnetic field-based sensing. The PEC tool uses electromagnetic fields to directly detect casing integrity and gas presence, eliminating the need for physical sample collection, degassing, and volumetric measurements, thereby achieving both high reliability and precision
Solution Approach 2:
The patent introduces electromagnetic fields as an intermediary to detect casing integrity and gas presence. Instead of directly measuring gas amounts in liquid samples, the electromagnetic field interacts with the casing and surrounding environment to provide indirect but reliable measurements of integrity conditions
2Difficulty of detecting and measuring
If EM logging tools are used for casing defect mapping, then detection capability is improved, but accuracy deteriorates due to ghost events and environmental complexities
Solution Approach 1:
The patent applies preliminary signal processing and calibration before actual defect detection. The system performs initial characterization of the electromagnetic environment and compensates for expected interference patterns (ghost events) in advance, allowing accurate defect mapping despite environmental complexities
Solution Approach 2:
The patent uses feedback mechanisms where the PEC tool continuously monitors electromagnetic responses and adjusts its measurements based on previously detected patterns. This feedback loop helps distinguish actual defects from ghost events by comparing expected versus actual electromagnetic signatures
3Reliability
If combined collocated and non-collocated sensor data processing is used, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
The patent segments the sensor system into collocated and non-collocated components, each serving specific measurement functions. The collocated sensors provide direct proximity measurements while non-collocated sensors provide contextual environmental data, and the segmented data processing handles each type appropriately to maintain reliability without unnecessary complexity
Solution Approach 2:
The patent creates a universal data processing framework that handles both collocated and non-collocated sensor data through integrated algorithms. This multi-functional processing system automatically selects and combines appropriate measurement techniques based on the specific evaluation context, achieving high reliability while managing complexity through standardized procedures
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
Accurately evaluates casing thickness and identifies defects in multiple casings by combining collocated and non-collocated sensor data, providing reliable and precise integrity assessments.
Implementation Method 1
exciting a cased hole configuration comprising a plurality of casings with a first electromagnetic field generated by a source. The first electromagnetic field excites a first series of currents in the plurality of casings, the first series of currents decay with time, the decayed first series of currents excite a second electromagnetic field
Implementation Method 2
acquiring signals with a plurality of receiving elements disposed in a vicinity of the source. The acquired signals correspond to the second series of currents
Data Source
AI summary
An inversion-based method has been developed to evaluate up to 5 or 6 nested casings by utilizing complementary sensitivities from time-domain collocated (relatively shallow) and multi-frequency, multi-spacing non-collocated (both relatively shallow and relatively deeper) pulsed eddy current measurements. Stand-alone inversion-based techniques are also disclosed to process time-domain collocated sensor measurements, which may come from single or multiple sensors of different lengths.