Rotating Spectral Density Tool for Annular Material Characterization
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Solution Overview
Problem
Current wellbore logging tools, such as pad-mounted spectral density logging tools, fail to provide accurate characterization of materials in the annulus between casing and wellbore due to limited circumferential coverage, leading to inaccurate determination of material presence and required cutting forces during plug and abandonment operations.
Innovation Solution
The implementation of circumferential spectral density logging tools that use a rotating mechanism with a radioactive source and detectors to provide complete circumferential coverage, distinguishing between solid, liquid, and gas components, and integrating with legacy acoustic and neutron measurements for improved material characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pad-mounted spectral density logging tools are used, then the tool structure is simple and easy to operate, but the circumferential coverage is limited and measurement accuracy is insufficient
Solution Approach 1:
The tool divides the circumferential measurement task into multiple segments by using multiple spectral density detectors positioned at different azimuthal locations (e.g., 0°, 90°, 180°, 270°) around the casing. Each detector measures a specific sector, and the combined data provides complete circumferential coverage, resolving the contradiction between measurement precision and device complexity by distributing the measurement function across multiple simpler detector units.
Solution Approach 2:
The invention transitions from single-point or limited-sector measurements to three-dimensional circumferential measurements by adding the azimuthal dimension. Multiple detectors are positioned at different angular positions around the casing, enabling full 360-degree coverage. This dimensional expansion allows accurate material characterization throughout the entire annulus without requiring an overly complex single-detector system.
2Measurement precision
If legacy acoustic measurements are used, then the measurement process is simple, but the ability to distinguish solids from other materials is insufficient
Solution Approach 1:
The invention merges legacy acoustic measurements with new spectral density measurements into a unified measurement system. The acoustic detectors continue to provide their traditional measurements while the added spectral density detectors provide complementary information about material composition. By combining these different measurement modalities, the system achieves superior material differentiation capability without completely replacing the simple acoustic measurement approach.
Solution Approach 2:
The measurement system uses a composite approach by integrating multiple types of detectors (acoustic and spectral density) that measure different physical properties of the annular materials. This composite measurement strategy allows differentiation between solids, liquids, and gases by analyzing multiple characteristics simultaneously, enhancing measurement precision while building upon the existing acoustic measurement infrastructure.
3Reliability
If complete circumferential coverage is achieved, then material characterization accuracy is improved, but the tool complexity and cost increase
Solution Approach 1:
The tool segments the circumferential measurement function into multiple independent detector units positioned at different azimuthal locations. Each detector is a relatively simple component that measures spectral density in its specific direction. By segmenting the measurement task across multiple simple detectors rather than using one complex omnidirectional detector, the system achieves complete circumferential coverage and improved reliability for operation planning while keeping individual component complexity manageable.
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 allows for more accurate characterization of the annular region, enabling better planning of rig operations and reducing costs by determining optimal cutting depths and managing expenses during well intervention.
Implementation Method 1
a first radioactive source positioned in a rotating portion of the circumferential spectral density logging tool while rotating the rotating portion and detecting the gamma radiation scattered by the material
Implementation Method 2
a first radioactive source positioned in a rotating portion of the circumferential spectral density logging tool while rotating the rotating portion
Implementation Method 3
a dual spaced neutron logging tool having a second radioactive source, a near neutron detector, and a far neutron detector
Data Source
AI summary
A method includes introducing a tool string into a wellbore having material disposed in an annular region surrounding the casing. Obtaining acoustic refracted waveform measurements of the material from a cement bond logging tool, obtaining ultrasonic measurements of the material from a circumferential acoustic scanning tool, obtaining gamma radiation measurements scattered from the material from a circumferential spectral density logging (RSDX) tool by emitting gamma radiation from a radioactive source in a rotating portion of the RSDX and detecting scattered gamma radiation using near and far spectral density detectors, and obtaining thermal neutron radiation measurements scattered from the material from a dual spaced neutron logging tool. A computer obtains measurements and generates a deliverable that includes one or more cross plots that identify a compositional equivalent of the material in an entire circumference of the wellbore.