Neutron Cement Evaluation Tool for Light Cement Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for evaluating cement behind a casing in wellbores, especially with lighter cements, are inefficient due to difficulties in detection using acoustic downhole tools, and there is a need for more effective means to ensure proper cement installation and zonal isolation.
Innovation Solution
A downhole neutron tool is used to emit neutrons that interact with the cement, causing it to emit a radiation spectrum, which is then measured to determine the presence and quality of the cement, allowing for accurate estimation of cement parameters through energy spectra and die-away patterns of gamma rays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If acoustic downhole tools are used to detect cement behind casing, then detection capability is improved for heavy cement, but detection precision deteriorates for light cement
Solution Approach 1:
The patent changes the detection parameter from acoustic impedance (used in acoustic tools) to neutron interaction properties. By measuring neutron capture cross-section and gamma ray spectra, the system can detect both heavy and light cement types with high precision, resolving the limitation of acoustic tools that work well for heavy cement but poorly for light cement.
Solution Approach 2:
The patent replaces the acoustic detection system with a nuclear physics-based neutron detection system. Instead of using acoustic waves that interact with mechanical properties, the system uses neutron radiation that interacts with nuclear properties (capture cross-section), enabling universal detection across different cement density types.
2Productivity
If lighter cement is used in well completion, then well performance is improved, but detectability using acoustic tools deteriorates
Solution Approach 1:
The patent introduces a neutron-absorbing material (such as boron or gadolinium) as an intermediary substance mixed with the light cement. This material has high neutron capture cross-section, acting as a tracer that enhances the cement's detectability via neutron tools while maintaining the desired light weight and performance characteristics of the cement.
Solution Approach 2:
The patent changes the detection approach from acoustic impedance measurement to neutron capture cross-section measurement. This parameter change enables detection of light cement that has low acoustic impedance but can be made detectable through its neutron interaction properties, especially when enhanced with neutron-absorbing materials.
3Measurement precision
If neutron tool is used to measure cement, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent designs a multi-functional downhole tool that performs both neutron capture cross-section measurement and acoustic impedance measurement. By combining multiple detection capabilities in one tool, the system achieves high measurement precision for cement parameters while reducing the need for multiple separate tools, thereby managing overall device complexity.
Solution Approach 2:
The patent segments the measurement process into distinct functional modules: a neutron source module, a gamma ray detector module, and an acoustic sensor module. This segmentation allows each module to be optimized independently while working together as an integrated system, managing complexity through modular design.
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 method enables precise detection and measurement of cement presence and thickness, improving the assessment of cement installation and zonal isolation, even with lighter cements, by utilizing neutron well-logging data in combination with acoustic impedance data.
Implementation Method 1
the neutrons interact with the particular material via inelastic scattering or capture of neutrons and cause the material to emit an energy spectrum of the gamma rays associated with the material
Implementation Method 2
the neutrons interact with the particular material via inelastic scattering or capture of neutrons and cause the material to emit an energy spectrum of the gamma rays associated with the material
Implementation Method 3
the time-based measurement of gamma rays or neutrons is influenced by the presence of the material
Data Source
AI summary
A method for evaluating cement in a cased wellbore in a geological formation includes placing a downhole tool into the cased wellbore, where the cased wellbore has been cased using a cement that contains a particular material. The method includes emitting neutrons using the downhole tool, wherein the neutrons interact with the particular material via inelastic scattering or capture of neutrons and cause the material to emit an energy spectrum of the gamma rays associated with the material or wherein the time-based measurement of gamma rays or neutrons is influenced by the presence of the material. The method includes using the downhole tool to detect radiation radiation, such as the energy spectrum of the gamma rays, or a die-away pattern of the gamma rays or neutrons that indicates a presence of the particular material and enable to estimate a parameter of the cement.