Nested Gamma Ray Detector in Drill Collar Insert
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Solution Overview
Problem
Existing gamma ray detectors in drilling operations face challenges such as collar attenuation effects and increased complexity and cost when placed in the outer wall of a drill collar, and they are less accessible for maintenance, while attempts to place them in a sonde have failed to provide accurate azimuthal measurements without shields, reducing detector counts.
Innovation Solution
A downhole assembly with a gamma ray detector positioned within a borehole in a drill collar, featuring an insert with a bore that allows for a larger, high-density scintillation crystal gamma ray detector, minimizing collar attenuation and enabling accurate azimuthal measurements by placing the detector inside the drill collar, which also improves maintenance accessibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gamma ray detector is placed in the outer wall of the drill collar, then collar attenuation effects are minimized, but tool design becomes more complex and expensive, and the detector becomes less accessible for maintenance
Solution Approach 1:
The gamma ray detector is nested within an insert that is positioned inside the drill collar bore, creating a hierarchical structure where the detector is protected and accessible while minimizing collar attenuation. The insert acts as an intermediate container that holds the detector in optimal position without requiring modifications to the drill collar outer wall.
2Device complexity
If the gamma ray detector is placed in a sonde in the bore of the collar, then tool design is simplified, but collar attenuation effects increase and azimuthal measurements cannot be provided
Solution Approach 1:
The insert is positioned locally within the drill collar bore at the optimal location for gamma ray detection, allowing the detector to have direct line of sight to the formation while minimizing collar attenuation. This localized positioning enables azimuthal measurements without requiring a shield that would reduce detector counts.
3Adaptability or versatility
If a shield is used to provide azimuthal measurements with a sonde-mounted detector, then azimuthal measurements are enabled, but detector counts are reduced
Solution Approach 1:
Instead of using a shield to block gamma rays for azimuthal measurements (which reduces counts), the detector is inverted to the insert position inside the drill collar where it can detect gamma rays from all azimuthal directions without attenuation, enabling azimuthal measurements with full detector counts.
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 configuration provides more accurate spectral gamma ray measurements, enhances detector count rates, and reduces costs by minimizing collar thickness and improving detector accessibility, allowing for robust and efficient formation parameter determination, including TOC and geosteering, while maintaining tool design simplicity.
Implementation Method 1
at least one sensor within the insert, wherein the sensor is a gamma ray detector
Data Source
AI summary
A downhole assembly includes a drill collar, the drill collar having an outer wall and an insert, the insert positioned within drill collar. The insert has a bore therethrough. The downhole assembly further includes at least one sensor within the insert, wherein the sensor is a gamma ray detector.