Gamma Ray Annulus Interrogation for Adhesion Assessment
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Solution Overview
Problem
In subterranean wellbores, the annulus between concentric tubulars often becomes adhered due to particulates in drilling fluids settling and forming a cement-like substance, making it difficult to remove the inner tubular without cutting below the adhesion point or leaving excessive pipe above, which existing methods cannot accurately assess or remediate.
Innovation Solution
A method using a gamma ray source and detector to investigate the annulus by directing radiation obliquely through the tubulars, scattering from both the annulus material and fluid, allowing for material identification based on detection rates and ratios, which remains consistent with changes in annulus thickness, enabling differentiation between solid and liquid materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If cutting tools are used to sever the tubulars, then the inner tubular can be removed, but the tubular cannot be removed if the cut is made at a depth below where the tubulars are adhered together
Solution Approach 1:
The patent replaces mechanical cutting operations with radiation-based detection to first identify the adhesion point depth. By using gamma ray sources and detectors to measure scattering patterns, the system determines the precise depth where tubulars are adhered together before any mechanical intervention, enabling planning of the cutting operation at the correct location.
Solution Approach 2:
The radiation detection system performs preliminary investigation to identify the adhesion depth before the cutting operation. This advance knowledge of the adhesion point location allows operators to plan and execute the cutting at the optimal depth, preventing the problem of cutting below the adhesion point which would leave the tubular stuck.
2Measurement precision
If a radiation source is directed along a path oblique to the tubular axis, then radiation can pass through the tubular into the annulus and scatter back for detection, but the detection must differentiate between scattering from annulus material and scattering from fluid in the tubular
Solution Approach 1:
The detection system segments the radiation detection into distinct pathways: one for detecting radiation scattered from the annulus material and another for detecting radiation scattered from the fluid in the tubular. By using multiple detectors positioned at different locations and angles, the system can distinguish between scattering sources and identify materials in the annulus with precision.
3Loss of information
If the radiation detection system is used to identify materials in the annulus, then accurate assessment of wellbore conditions is achieved, but the system requires differentiation between solid and liquid materials based on detection rates
Solution Approach 1:
The system exploits parameter changes in radiation scattering behavior between solid and liquid materials. By measuring detection rates and analyzing how radiation scatters differently from solids versus liquids, the system can differentiate between cement (solid) and drilling fluid (liquid) in the annulus, recovering complete information about annulus contents.
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 effectively identifies materials in the annulus, such as lightweight cement, by maintaining consistent detection ratios regardless of thickness changes, facilitating accurate assessment and remediation of wellbore conditions.
Implementation Method 1
directing gamma rays from the source so that some of the gamma rays travel into the annulus and scatter from a material in the annulus back into the inner tubular
Implementation Method 2
The radiation is directed along a path that is oblique to an axis of the tubular allowing some of the radiation to pass through the tubular into an annulus circumscribing the tubular and scatter back into the tubular
Data Source
AI summary
Monitoring scattered gamma rays is used to identify substances disposed between coaxial tubulars disposed in a subterranean wellbore. Gamma rays are strategically directed from within an inner most tubular and into the annulus, some of the gamma rays scatter from the substance between the tubulars and are detected with detectors set a designated axial distance from the gamma ray source. Gamma rays also scatter from fluid within the tubular, a ratio of the gamma rays detected that scatter from the fluid in the tubular and from the substance can be used to determine the substance.