Rotating Gamma Scanner for Azimuthal Downhole Cement Inspection
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Solution Overview
Problem
Existing downhole inspection tools lack azimuthal information in multistring completions due to collimated gamma ray sources and detectors, making it challenging to detect defects and properties in wellbore components like cement layers and casing.
Innovation Solution
A gamma scanner system with synchronized rotation of source collimator and detector aperture provides azimuthal information by emitting radiation in a directionable manner, allowing for defect detection through multiple layers in multistring completions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a collimated gamma ray source and detector are used, then the radiation can be directed in a certain direction, but azimuthal information is lost
Solution Approach 1:
The patent implements dynamic rotation of the collimated gamma ray source and detector assembly around the wellbore axis. By making the previously static collimated system dynamic and rotatable, the invention captures azimuthal information at multiple angles while maintaining the directional radiation capability provided by collimation.
Solution Approach 2:
The invention adds the azimuthal dimension to the measurement system by rotating the collimated source-detector assembly. This transforms a one-dimensional directional measurement into a three-dimensional measurement that captures information in the radial, axial, and azimuthal directions.
2Ease of manufacture
If the source and detector are collimated for directional radiation, then radiation can be sent in a certain direction, but multiple logging runs are required to obtain complete information
Solution Approach 1:
By implementing continuous rotation of the collimated source-detector assembly during a single logging run, the system captures directional radiation data at multiple azimuthal positions simultaneously, eliminating the need for multiple separate logging runs and improving productivity.
Solution Approach 2:
The invention maintains continuous useful action by rotating the collimated source-detector assembly throughout the logging operation, ensuring that directional radiation measurements are continuously acquired across all azimuthal angles in a single pass through the wellbore.
3Ease of manufacture
If traditional collimated gamma ray instruments are used, then directional radiation is achieved, but detection of defects behind multiple layers becomes challenging
Solution Approach 1:
By adding azimuthal rotation to the collimated gamma ray instrument, the system can probe defects behind multiple layers from different angular perspectives. This dimensional addition enables the detection and localization of defects in complex multistring completions where layers are stacked radially.
Solution Approach 2:
The dynamic rotation of the collimated source-detector assembly allows the radiation to penetrate through multiple layers at various angles, improving the ability to detect defects behind cement layers, casings, and other intermediate structures that would block or attenuate radiation from fixed directions.
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
Enables efficient and accurate detection of defects and properties in cement layers and casing by obtaining azimuthal information, reducing the need for multiple logging runs and minimizing sinusoidal variations in count rates.
Implementation Method 1
the at least one source emitting radiation into the multistring wellbore
Implementation Method 2
the at least one detector receiving backscatter radiation
Data Source
AI summary
A method for identifying a defect within a cement layer of a multistring wellbore includes deploying a gamma scanner into the multistring wellbore, the gamma scanner including at least one source and at least one detector, the at least one source emitting radiation into the multistring wellbore and the at least one detector receiving backscatter radiation. The method also includes obtaining, from the gamma scanner, a count rate associated with at least one region of interest of the multistring wellbore. The method further includes identifying, based at least in part on data acquired from the gamma scanner, a background profile for the multistring wellbore. The method includes removing the background profile from the count rate. The method further includes identifying, within the at least one region of interest, a defect within the cement layer.